The patient: A man in his 50s in Nottingham, England

The symptoms: The man suddenly developed numbness on his left side, as well as unsteadiness.

What happened next: Upon the man's admission to a hospital, his blood pressure was found to be 254/150 millimeters of mercury (mm Hg), according to a report of the case. That extremely high reading indicates a hypertensive crisis. A neurological exam confirmed that he had numbness across the entire left side of his body and that he had trouble coordinating movements with his left arm and leg.

A CT angiogram — a scan that details the blood vessels, including blockages and damage — showed signs that the man may have experienced a sudden spasming and narrowing of the cerebral arteries, an event known as reversible cerebral vasoconstriction syndrome (RCVS). Additionally, an MRI showed tissue death in the thalamus, which acts as a relay station for motor and sensory information; specifically, he had damage in the thalamus located on the right side of the brain.

There were no other notable findings on the patient's exam, and his medical history lacked any history of smoking, alcohol use or substance abuse. The report describes him as "normally fit and well."

The diagnosis: The man was diagnosed with a right thalamic lacunar stroke. A lacunar stroke happens when a blood vessel that carries blood to one of the brain's deep structures gets blocked. Right-sided strokes affect the sensation and movement on the left side of the body, and vice versa.

The treatment: The man was treated with a combination of physiotherapy and occupational therapy while at the hospital, and he began taking blood thinners to help prevent another stroke. He also began taking a cholesterol-lowering drug and blood-pressure-lowering medications.

The man had several follow-up appointments over the next three months. "He appeared to have made an excellent functional recovery, although the sensory symptoms [of numbness] were persistent and deteriorated throughout the day," his doctors noted. His blood pressure had also remained persistently high, so he began taking additional blood-pressure drugs.

At that point, the doctors asked the patient more questions about his lifestyle and learned that he consumed an average of eight cans of a "high-potency" energy drink each day. Each can contained 160 milligrams of caffeine per 16 fluid ounces, adding up to about 1.2 grams of caffeine a day. (Less than 400 milligrams is considered a safe daily dose of caffeine.)

The patient was advised to stop consuming energy drinks, and his blood pressure quickly fell to normal levels. He was able to stop taking all of his prescribed medications within three weeks of quitting the drinks.

"Further follow-up at 3 and 6 months showed complete resolution of hypertension and a complete recovery from the stroke with full return to work," his doctors reported. Eight years later, he had had no further strokes, though he still had lingering sensory issues on his left side from the first stroke.

What makes the case unique: Although he was otherwise healthy, the man's excessive consumption of energy drinks appeared to have driven his high blood pressure and subsequent stroke.

The case report authors noted that the high caffeine levels were likely a big culprit, but they hypothesized that other common ingredients in energy drinks may have contributed to the stroke risk. For instance, when combined with caffeine, taurine and guarana may amplify the stimulant's blood-pressure-boosting effects and its effects on blood-vessel constriction, they theorized. Taurine, an amino acid, is often added to energy drinks for its purported ability to increase exercise capacity, while guarana is a plant that is similarly perceived to have health benefits and whose seeds contain caffeine.

Additionally, the high sugar content of many energy drinks may further raise the risk by causing inflammation and dysfunction in the lining of blood vessels.

The authors cited a handful of published medical case reports in which the excessive consumption of energy drinks or of individual energy drink ingredients was tied to cardiovascular issues, including dangerously high blood pressure.

They concluded that "both acute and chronic intake" of energy drinks may increase the risk of cardiovascular disease and stroke.

"Healthcare professionals should consider specific questioning related to ED [energy drink] consumption in young patients presenting with stroke or unexplained hypertension," they concluded. Importantly, the risk seems to be reversible, they added, given that quitting energy drinks appears to resolve the related problems.

For the patient's part, he said, "I obviously wasn't aware of the dangers drinking energy drinks were causing to myself. [I] have been left with numbness [in my] left hand side hand and fingers, foot and toes even after 8 years."

For more intriguing medical cases, check out our Diagnostic Dilemma archives.

This article is for informational purposes only and is not meant to offer medical advice.

Missing your morning coffee is a headache — literally. Though caffeine is often used to kick-start a day or deliver an energy boost, a sudden drop in consumption can cause painful headaches. And for those trying to kick a coffee habit entirely, the pain can be particularly agonizing.

"Caffeine withdrawal headaches can be surprisingly intense," Dr. Nolan Pearson, a neurologist and headache specialist at Cedars-Sinai Medical Center in Los Angeles, told Live Science. "It can trigger a migraine-type headache, so it can be pulsing, pounding, throbbing."

But why is caffeine withdrawal so excruciating? Neurologists still aren't entirely sure, but they have a few theories and some tips on how to treat these nasty headaches.

Caffeine withdrawal headaches occur after a person consumes more than 200 milligrams of caffeine — the amount in about two cups of coffee — per day for more than two weeks and then abruptly stops, according to the International Classification of Headache Disorders (ICHD-3). The headaches usually appear within 24 hours without caffeine, and typically go away within one week or when caffeine is consumed again.

Why withdrawal headaches are so painful remains somewhat unclear. Because caffeine affects many parts of the body, experts haven't been able to pin down a single overarching cause. But the pain likely comes, in part, from dilated blood vessels.

Caffeine constricts blood vessels — which is part of the reason why the drug can also, paradoxically, be used to relieve some types of headaches, according to the Mayo Clinic. When caffeine use stops, those blood vessels swell, causing more blood flow and, therefore, pain. But Dr. Brian McGeeney, a neurologist and headache specialist at Boston's Brigham and Women's Hospital, said that's just one contributing cause.

"It's involved, but it's not the whole story," he told Live Science.

Related: Does caffeine help or cause headaches?

Another explanation for caffeine withdrawal headaches has to do with adenosine receptors. The drug blocks adenosine, a building block of RNA, from attaching to receptors scattered across the central nervous system. This causes neurons to fire more quickly and blood vessels to constrict, which, in turn, makes people feel more alert and awake.

When someone stops consuming caffeine, the sudden buildup of adenosine in the body can contribute to withdrawal headaches. This is also why caffeine is commonly used to treat headaches: By blocking adenosine receptors, it prevents blood vessel dilation from the outset. In fact, caffeine can make painkillers like ibuprofen and acetaminophen work more efficiently, according to the Mayo Clinic.

But, as Pearson noted, much of caffeine withdrawal is yet to be explained. "We certainly don't know, but these are all reasons why it might be causing headaches," he said.

Caffeine withdrawal often happens in hospital settings when patients have to quit their coffee habit to undergo a medical procedure. Some studies also show caffeine withdrawal symptoms in people who fast, such as Muslims observing Ramadan.

"When life is interrupted unpredictably, like you end up in the emergency room or get admitted to hospital, you see a lot of caffeine withdrawal," McGeeney said.

Caffeine is usually safe in moderation. But when someone is looking to reduce or eliminate their caffeine intake, experts agree that the best strategy is to cut down gradually. Drink a little less each day, or substitute lower-caffeine alternatives, like tea, to make the transition easier.

"If somebody's using caffeine chronically and they want to cut back, I would do it quite gradually," Pearson said. "So no faster than about 25 to 50 milligrams of caffeine reduced per day — that's a quarter to half a cup of coffee."

If a headache lasts longer than a week, Pearson recommended seeking medical care, as that time frame suggests the headache may be triggered by something other than caffeine withdrawal.

This article is for informational purposes only and is not meant to offer medical advice.

Caffeine may help some bacteria keep antibiotics out of their cells, potentially reducing the therapeutic effects of the drugs, a new laboratory study hints.

However, experts caution that it's not yet clear how this effect might play out in humans, so caffeine drinkers needn't panic yet.

Scientists have known for decades that bacteria can protect themselves by pumping out harmful substances through special transport proteins in their outer layers — and this ability helps bacteria resist the effects of drugs that would otherwise kill them. However, it wasn't clear how bacteria change the activity of the genes behind these transport proteins in response to molecules they encounter.

To learn more, researchers tested how the common gut bacterium Escherichia coli — better known as E. coli — responded to 94 different chemical compounds, including antibiotics and aspirin, as well as products made in the gut, like secondary bile acids. They also looked at small molecules found in common foods, such as vanillin, the compound that gives vanilla its flavor, and caffeine.

Their study, published July 22 in the journal PLOS Biology, showed that many different chemicals can trigger changes in bacterial transport-related genes and thus potentially affect their response to antibiotics.

Related: Superbugs are on the rise. How can we prevent antibiotics from becoming obsolete?

For example, caffeine was found to reduce the production of a transport protein called OmpF, which helps bring common antibiotics — like ciprofloxacin and amoxicillin — into bacterial cells' membranes or innards. In theory, with fewer of these OmpF proteins available, the antibiotics cannot access their targets within the cells as easily, making them less effective.

But this finding shouldn't worry coffee drinkers just yet — there are many potential variables that haven't been studied yet, said April Hayes, a postdoctoral researcher at the University of Exeter who was not involved in the study. "This would include whether the effect of caffeine would reduce the body's ability to clear infections," Hayes told Live Science.

Andrew Edwards, a professor of molecular microbiology at Imperial College London, agreed that "there's no evidence from this study that drinking coffee will affect a person's response to antibiotics and nobody should change their routine." Edwards, who was not involved in the study, said he recommends that people prescribed antibiotics follow their doctor's guidance and the instructions that come with the medicine.

Adaptable microbes

In the study, researchers at the University of Tübingen in Germany looked at how seven genes involved in transport inside E. coli responded to different chemicals. Out of the 94 substances they tested, 28 changed the activity of these genes.

The chemicals that had an effect included caffeine; the weed killer paraquat; and certain classes of antibiotics, like tetracyclines and macrolides. Drugs that block folic acid, which are used to treat some cancers and inflammatory diseases, and salicylates, a broad class of drugs that includes aspirin, also had an effect.

"This study adds to a growing appreciation that bacteria can sense and respond to numerous different stimuli … all of which can affect the susceptibility of the microbe to antibiotics," Edwards said.

One-third of the chemical-induced genetic changes involved the Right-origin-binding protein ("Rob," for short), which switches genes on or off by binding to specific DNA sequences. The findings suggest that Rob plays a bigger role in helping E. coli adapt to its environment than previously thought.

For now, though, it's still unclear exactly how caffeine changes gene activity in E. coli or interacts with Rob at the molecular level. Additionally, the researchers don't yet know whether the effects seen in lab experiments happen the same way during real infections in people.

In the study, the researchers found that caffeine's ability to interfere with how antibiotics work also applied to a strain of E. coli sampled from a real patient with a urinary tract infection. This lab experiment suggests the effect of caffeine on bacteria could have important implications for human health — but again, that will need to be confirmed in future research.

Future research could also look at microbes beyond E. coli. The researchers suspect their findings may also have implications for how other bacteria tweak their transporters over time.

But importantly, "at this point, it still seems highly unlikely that consuming caffeine would result in a difficult-to-treat infection," Hayes said. "Overall, this study is interesting, but is not a cause for concern for caffeine consumers."

This article is for informational purposes only and is not meant to offer medical or dietary advice.

The human body continues to surprise doctors, who report meeting patients with rare conditions or unique abilities. In this list, we take a look at 32 unusual medical cases reported throughout the years, zooming in on the patients' symptoms and outcomes. 

Not all of the cases are fully explainable, but in many of them, doctors determined the causes of the unusual conditions. A prompt diagnosis followed by the appropriate treatment meant a number of patients in these stories recovered, but some of the cases were fatal.

Cement in a man's heart

A 4-inch (10 centimeters) piece of cement got lodged in the heart of a 56-year-old man after traveling through his bloodstream after a surgical procedure.

The man was admitted to the emergency room after experiencing chest pain and trouble breathing for two days. An X-ray and CT scan confirmed that a foreign object was in his heart. During surgery, doctors found the object, which turned out to be a sharp, thin piece of cement that had torn through the upper-right chamber of the man's heart and punctured his right lung.

The cement had come from a procedure the man had a week earlier to treat a broken vertebra. Doctors injected a special type of cement to restore his vertebra. Although this procedure is usually safe, in this case, the cement leaked from the bone into the patient's veins. The cement then hardened and traveled through the man's bloodstream to his heart. He recovered a month after the surgery to remove the cement.

Green "furry" tongue

A man found that his tongue was sprouting green "hairs" after he developed a benign condition known as hairy tongue. Lingua villosa, as it is also called, happens when the tiny bumps on the tongue, called papillae, don't shed as they normally would and thus grow beyond their normal length, which is usually around 0.04 inch (1 millimeter) long. As the bumps grow, they turn a particular color — typically green, brown, white, green or pink — depending on the food, bacteria and other material they encounter.

The condition is fairly common, affecting about 13% of people at some point in their lives. Eating soft foods and drinking large amounts of coffee, tea or alcohol can increase the risk of developing hairy tongue. The 64-year-old in this case followed his doctors' instructions to scrub his tongue daily with a toothbrush, and his tongue turned back to normal in six months, the case report noted.

Fetus in a toddler's brain

Doctors surgically removed a fetus that was found in the brain of a 1-year-old girl. 

This rare condition, called intraventricular fetus in fetu, was discovered after the child developed an enlarged head and had delayed motor skill development. The fetus came from the same fertilized egg as the girl, so if the fetus had developed normally, it would have been her identical twin. However, when one fetus envelops the other, the absorbed twin typically stops developing.

Fetus-in-fetu is very rare, occurring in only about 1 in 500,000 births. Most cases of the phenomenon happen in the abdomen, rather than the head. 

Student able to change pupil size

Most of us can't tell what our pupils are doing, as usually, they automatically dilate in the dark to let in more light and constrict in bright environments to limit the amount of light that flows through them. However, one student in Germany found he could enlarge and shrink his pupils voluntarily.

The 23-year-old told researchers that constricting his pupils felt like tensing something, while making them larger felt like he was fully relaxing his eyes. At first, he changed his pupils' sizes by focusing in front of or behind an object, and then with practice, he learned how to do it simply by concentrating on his eyes. Although some people can achieve this effect indirectly, such as by thinking about the sun, researchers couldn't find any indication that the student was using such a method.

Man living normally with small brain

A 44-year-old man who worked as a civil servant was leading a normal life, despite his brain being at least half the average size.

This case was described in the journal The Lancet after the man sought medical help because he had felt weakness in his left leg for two weeks. When he was 6 months old, doctors had placed a shunt in his head to relieve fluid buildup in his brain. At age 14, he lost full control of his left leg but recovered it after the shunt was altered. His neurological development and the rest of his medical history were otherwise normal.

However, after he sought medical help for the weakness in his leg, brain scans showed several abnormalities. His condition caused a buildup of fluid in his skull, which left him with just a thin sheet of brain tissue, because the fluid left little room for brain tissue. Feeling returned to his leg after a new shunt was inserted to drain the excess fluid.

Teen speaking only in a foreign language

A 17-year-old in the Netherlands lost his ability to speak and understand Dutch for 24 hours after an orthopedic surgery. During this case of foreign language syndrome (FLS), he could communicate only in English, which he'd never spoken outside of a classroom.

According to the case report, it started when the teen went to the hospital for knee surgery following an incident during a soccer game. This was his first time being operated on and undergoing general anesthesia. When he woke up, he was confused and thought he was in the United States, specifically Utah. A psychiatrist confirmed that the teen could answer questions only in English — adequately but not fluently. 

When friends came to visit him around 24 hours after the surgery, the boy spontaneously began to understand and speak Dutch again. During a mental exam the next day, the teen said he could remember himself only speaking and understanding English. However, it could be that he thought this because he was told about the incident.

The authors of the case report believe this was the first scientifically reported case of FLS in a child or adolescent. It's unclear what caused the teen to experience FLS, but the authors hypothesized that it might have been linked to the anesthetic he was given. 

Severe side effect of holding in a sneeze

A man in his 30s was driving when he felt the urge to sneeze. He stifled his sneezes by pinching his nose and closing his mouth but immediately felt severe neck pain. When he went to the ER, a CT scan of his neck and chest revealed a quarter-inch-long (half a centimeter) tear in his trachea, or windpipe.

Doctors decided against surgery, since the man's vital signs were otherwise normal. Nevertheless, the patient was kept under observation. Five weeks after he was discharged, a follow-up CT scan showed that his trachea had healed. 

"We suspect the trachea perforated due to a rapid build-up of pressure in the trachea while sneezing with a pinched nose and closed mouth," the care team wrote in the journal BMJ Case Reports. They advised people not to stifle sneezes in this way. 

Girl born with hair all over her body

Since birth, a 2-year-old girl had hair all over her body, except on her palms, soles, mouth, eyes and nose.

In a report of the case, doctors noted that the girl had no other complications related to the condition, known as congenital generalized hypertrichosis terminalis. The main reason she was brought in for medical attention was that her parents were alarmed by her physical appearance. Doctors assured her parents that the condition was benign and listed some hair-removal options for the child.

Allergy to water

In an extremely rare case, an 18-month-old was diagnosed with an allergy to water, known medically as aquagenic urticaria. Within just 15 seconds of coming into contact with water, she experienced severe skin reactions, including hives and rashes.

The exact cause of this condition remains unknown. Some theories suggest the hives could be caused by a substance that's dissolved in the water, such as chlorine, rather than the water itself, or that something on patients' skin produces a toxic substance when it touches water.

Baby's changing eye color

A 6-month-old's eyes turned from brown to a deep indigo blue after he was given the antiviral favipiravir to treat COVID-19. 

Favipiravir stops viruses from replicating their genetic material. Less than a day after the antiviral drug was given to the infant, his eyes started shining blue in the sunlight. A medical examination revealed a buildup of blue pigment in both of his corneas — the clear, outer part of the eye. Five days after the antiviral was stopped, the boy's eyes returned to their original brown.

The blue may have been caused by the buildup of fluorescent chemicals in the cornea as the drug was broken down by the body, the case report authors suggested.

The dancing plague

One of the greatest unsolved mysteries of public health is what caused the three-century-long "dancing plague" in Europe.

Starting in the 13th century, people in Germany, the Netherlands and Italy would reportedly gather in large crowds and dance frantically until they got exhausted or died. As many as 1,100 people would take part in each gathering. There are detailed accounts of such dancing plagues in literature, but the exact cause remains unknown. It's likely that this dancing plague, or choreomania, was triggered by a combination of factors.

Historical accounts suggest that it was a mass psychological phenomenon triggered by social adversity and that it presented itself in the form of dancing due to the underlying culture of the period.

Fatal insomnia

A patient was sleeping only two to three hours a night in a case of fatal familial insomnia (FFI). The 57-year-old man had experienced progressive memory decline for one year before being admitted to the hospital. During the day, he often felt weak and often ended up falling asleep when he was sitting or lying down. His ability to use chopsticks worsened quickly, he developed issues walking soon afterward. The man died a few months after being admitted to the hospital.

FFI is a type of hereditary prion protein disease for which there's no effective treatment. Prion diseases occur when cells make dysfunctional proteins that accumulate in the brain, leading to progressive damage. The symptoms of FFI include insomnia, movement disorders and hormonal shifts. Tests usually reveal mutations in a gene called PRNP; one mutation called D178N is tied to both FFI and a second prion disease.

Police officer who recognized everyone

"Where do I know you from?" a police officer kept asking strangers. The 46-year-old had developed intermittent episodes of anxiety each lasting about 15 seconds; six months after these episodes began, he had a seizure. His MRI results and neurological exam were normal. However, a month after the seizure, he reported new symptoms. In addition to memory problems, he experienced an odd phenomenon: Every person he saw looked familiar.

A case report detailed how the officer's "hyperfamiliarity" also occurred to a lesser extent with faces in photos and on TV, but not with voices. Patients with hyperfamiliarity for faces (HFF) quickly realize that they're mistaken. They usually have lesions on the left hemisphere and temporal lobe of the brain, but the right hemisphere and frontal areas of their brains remain normal.

The left hemisphere is involved in identifying unique facial features, while the right is known to link  faces with emotional and personal meaning. Thus, HFF may occur when the left hemisphere is impaired and the right hemisphere overcompensates, leading to a false sense of familiarity. The authors of the report suggested that HFF is more common than suspected, since the vast majority of cases likely go unrecognized. 

Giant kidney worm

A young man went to the ER because he couldn't pee and he'd had a fever for two days. His vitals were normal except for a rapid heart rate. Hospital staff placed a catheter and gave the man IV fluids and a combination of drugs. But on his second day in the hospital, the patient found a worm in his urine bag. 

The hospital's microbiology department confirmed that the worm — which was red and almost 12 inches (30 cm) long — was the rare parasite Dioctophyma renale. When his urine was analyzed, no traces of the parasite's eggs were found. Although doctors advised against it, the man left the hospital after he had passed the worm.

D. renale is one of the largest known parasitic nematodes. It's found mostly in the kidneys of flesh-eating mammals, like dogs and wolves, which then excrete its eggs in their urine. Humans could get infected by eating raw or undercooked fish or frogs containing the larvae. In this particular case, the patient had eaten raw fish from a lake close to his home. It wasn't the first time he'd passed such worms. In complicated cases, the only treatment is for the infected kidney to be removed.

Related: 32 scary parasitic diseases

Child who ate "everything except food"

In a case report, doctors described how a 7-year-old girl reported to their department with a history of abdominal pain for three years, worn down teeth and cavities. The girl had been eating pieces of bricks for five years, despite warnings from her parents. 

It's common for babies to go through a temporary period of putting all kinds of things in their mouths. However, when a child past this phase starts eating things that aren't food again, there's cause for concern. When people start eating nonfood items such as stones, bricks, chalk and soap, the condition is known as pica. Possible causes of pica include iron deficiency and lead exposure. 

The child in the case report was given iron, zinc and calcium supplements, and her habit stopped after six months. 

Double teeth

When a 14-year-old boy went in for a routine dental checkup, dentists found that his left first premolar had two crowns. He had no symptoms related to the tooth and did not want any treatment for it, according to the report of the case.

Tooth gemination, commonly known as "double teeth," is a development disorder of a tooth's shape coming from a single tooth germ's unsuccessful attempt to divide. The exact cause of gemination is unknown, but environmental factors such as trauma or vitamin deficiencies may play a role.

Mermaid syndrome

A report describes the case of a baby with sirenomelia, also known as "mermaid syndrome," a condition in which a baby is born with a single middle lower limb instead of two legs. The baby was born with fused lower limbs and fused feet, which were rotated and aligned abnormally, making them resemble fins. The baby was transferred to a neonatal unit but died after seven hours of life.

Risk factors for mermaid syndrome include maternal diabetes and drug abuse, but the exact cause remains unknown.

Woman who couldn't feel pain

A 58-year-old woman had a long history of insensitivity to pain and recalled how, as a child, she would get cuts that she could not feel. She also did not feel pain when touching extremely hot or cold water, although she could tell the difference between the two, her doctors described in a case report. The woman, who has two children, didn't feel pain during childbirth, either.

She was diagnosed with a condition called congenital insensitivity to pain (CIP), a rare disease caused by mutations in the SCN9A gene. People who have CIP can feel different sensations but can't perceive pain.

Similar to others with CIP, the woman had anosmia, meaning she couldn't smell.

Persistent hiccups

While hiccups usually end on their own after a short while, that's not always the case. In fact, almost 4,000 people are admitted to the hospital in the United States for hiccups every year. 

A 22-year-old male reported having hiccups all day for two years. Past medical treatments, which were not described in the report, did not help. Due to his chronic hiccups, he quit his job and his social life broke down. He also started feeling abdominal pain and had anemia.

Eventually, he chose to undergo surgery to treat his gastroesophageal reflux, which was thought to be causing the hiccups, and he hiccuped throughout the procedure. Although the frequency of his hiccups decreased after the surgery, he wasn't entirely cured. While it's often not possible to identify a single cause for chronic hiccups, some cases include gastroesophageal reflux disease and adrenal insufficiency. 

Giant, lung-shaped blood clot

A man was admitted to the intensive care unit when his symptoms of chronic heart failure suddenly worsened. After admission he started coughing up blood and also had trouble breathing. He was given blood-thinning medication, which increased his risk of bleeding, for the serious heart condition. At one point, he started coughing violently — and he hacked up a giant blood clot in the shape of part of his lung. Basically, it was a mold of clotted blood in the shape of a branched airway called a bronchial tree. 

The 36-year-old man died a week later due to complications of heart failure. Doctors published the image of the blood clot in a case report in The New England Journal of Medicine.

Navy-blue blood

One night, a 25-year-old woman in Rhode Island applied large amounts of numbing medication to a tooth that was hurting her. The next day, she went to the ER because she felt weak and fatigued, was experiencing shortness of breath and had skin discoloration.

When her blood was drawn, it appeared a deep, navy blue instead of red. According to the case report, the woman had a condition called methemoglobinemia, where there's an increased level of a type of hemoglobin called methemoglobin, which, unlike the regular form of hemoglobin, can't carry oxygen to the rest of the body. 

The condition can be either congenital or a side effect of some drugs, including some anesthetics. The woman was quickly treated with intravenous methylene blue, which improved her breathing and reduced her skin discoloration. The medication helped by restoring iron to its proper form within her blood, and in this case, the woman made a complete recovery.

Beer-making belly

A man was arrested for "drunk driving" even though he insisted he hadn't been drinking. After this incident, he went to an Ohio clinic, where doctors found strains of Saccharomyces boulardii and Saccharomyces cerevisiae, known as brewer's yeast, in his stool samples.

It turned out that the man had a condition called auto-brewery syndrome, in which microbes in the gut transform carbohydrates into alcohol, according to a case report in the journal BMJ Open Gastroenterology. This diagnosis also explained why he had episodes of mysterious drunkenness and "brain fog." The man was cured after doctors placed him on antifungal agents and a carbohydrate-free diet for six weeks.

Sudoku-triggered seizures

In a puzzling case, a German man developed seizures while trying to solve a Sudoku brainteaser.

According to the report of the man's case, he hadn't always reacted this way to Sudoku. During a ski trip in 2008, he was buried in the snow by an avalanche, knocked unconscious and then given CPR. The man survived, but because his brain was deprived of oxygen for 15 minutes, he developed muscle jerks in his mouth and legs. After being given anti-epileptic medication, he started to recover.  

But while trying to solve a Sudoku puzzle at a rehabilitation facility, the man started experiencing involuntary jerking motions, called clonic seizures, in his left arm. Doctors later discovered that the seizures were triggered when the man imagined the numbers in Sudoku grids in three dimensions, which reportedly helped him solve the puzzles. Unfortunately, that put an end to the man's hobby, as it was the only way he could avoid the seizures.

Teeth in a baby's brain

A 4-month-old boy was taken for medical tests because his head appeared to be growing faster than what was normal for his age. A brain scan confirmed that he had a brain tumor. However, during brain surgery to remove the tumor, doctors found that it contained several fully formed teeth, according to the case report.

It turned out that the child had a craniopharyngioma, a rare type of benign brain tumor. After the surgery, his doctor said the boy was "doing extremely well, all things considered."

Long-lost contact lens found decades later

While playing badminton, a 14-year-old girl was hit in the eye with a shuttlecock. She was wearing a contact lens, which she couldn't find; she assumed it fell out of her eye and was lost. However, she was in for a surprise when she went to the doctor due to swelling in her left upper eyelid 28 years later.

An MRI showed a cyst, which was surgically removed. When it was removed, the cyst burst — and there, lo and behold, was the long-lost contact lens, her doctors explained. It turned out that during the badminton injury, the lens migrated to the woman's left upper eyelid, where it remained hidden for 28 years.

Baboon syndrome

Penicillin is one of the most commonly used antibiotics globally, but as with any other drug, it can have side effects. A 40-year-old man with a sore throat was given penicillin to treat tonsillitis. Days later, he developed a rash on his armpits, groin and buttocks in a case of "baboon syndrome," named after its resemblance to the red coloration on the rears of some monkeys.

The condition, formerly called "symmetrical drug-related intertriginous and flexural exanthema," is usually caused by an allergic reaction to penicillin or other substances, such as mercury. According to the man's case report, the rash disappeared after his medication was changed.

Temporary wrinkles

When a man put his hands in water, he developed "excessive wrinkling" on his hands that would disappear around 30 minutes after they dried, according to a case report in the journal JAMA Dermatology. 

The condition, called aquagenic syringeal acrokeratoderma (ASA), is a rare skin disease that usually occurs in young women, but in this instance, it affected a man in his 20s. It occurs mostly in people with cystic fibrosis.

The man sought medical help after experiencing the condition for three years, with the skin on his hands becoming swollen, wrinkly and scaly whenever they made contact with water. The man's palms were unaffected, which is unusual, but he was nonetheless diagnosed with ASA. He was treated with an ointment containing a corticosteroid and moisturizer, and his symptoms started improving within a month.

Accidental caffeine overdose after measuring error

An error while measuring caffeine powder had fatal consequences for a man in the U.K. The 29-year-old personal trainer ordered a small bag of caffeine powder to add to his drinks. Although he meant to add up to 300 milligrams (0.01 ounce) of the powder, the scale he used had a starting weight of 2 grams (0.07 oz). Immediately after consuming his drink, he felt his heart beating fast, and he started foaming at the mouth. His wife called an ambulance, but the man died later that day.

At the time, the coroner found a caffeine level of 392 milligrams per liter in the victim's blood — the equivalent of about 100 to 200 cups of coffee. The coroner said it appeared that the man was aiming for the middle of the range of the recommended caffeine dose but got his calculations wrong.

Folded stomach

Doctors managed to save a girl's life after she developed a rare and potentially life-threatening condition called gastric volvulus, in which part or all of the stomach rotates by more than 180 degrees. When this happened to the 12-year-old girl, she was left in crippling pain, could not breathe properly and couldn't pass stools.

Gastric volvulus can lead to an obstructed stomach, blocking the movement of food, blood and oxygen. According to the report of her case, the girl survived, thanks to the prompt diagnosis and surgical treatment. However, the condition is fatal in about 30% to 50% of cases.

Gastric volvulus is usually caused by a hernia, in which part of the stomach pushes into the chest cavity through an opening in the diaphragm. However, in the girl's case, the stomach folded over itself because the ligaments anchoring her stomach in place were loose.

Tumor in "extra" breast

A 63-year-old woman felt painful swelling in her armpit and sought medical help. Doctors saw that she had a mass of tissue, which an ultrasound revealed was an "extra breast." However, doctors also found a spherical tumor growing in one of the milk ducts in the extra breast. The tumor was benign and was successfully removed, according to the patient's case report.

This kind of tumor affects up to 3% of people in their normal breast tissue, but it is not commonly found in extra breast tissue. Polymastia, which refers to having extra breast tissue, is a relatively common condition, affecting up to 6% of females and 3% of males.

Diver's leaky blood vessels

Scuba divers plan their rate of ascent to avoid decompression sickness (DCS), which can be life threatening. DCS happens when dissolved gases in a person's blood form bubbles in a person's bloodstream and tissues. A diver's rapid ascent from a high-pressure environment in the deep sea to the lower pressure at the surface could trigger DCS. Symptoms include joint pain, nausea and headaches.

One diver had an extremely rare complication of DCS in which fluid started flowing out of his cells, doctors explained in the journal BMJ Case Reports. The man, who was in his 40s, went to the ER with shortness of breath after a 100-foot (30 meters) dive. While doctors might have suspected DCS, an expert on systemic capillary leak syndrome (SCLS) identified the diver's symptoms and helped provide the appropriate treatment for the complication.

It was suspected that air bubbles formed in the patient's blood vessels, triggering a "pro-inflammatory cascade which made the vessels more permeable, resulting in the leakage of protein and fluid," the expert said at the time. SCLS can be fatal, but in this case prompt diagnosis and treatment meant the diver was discharged in less than a week.

Locked-in syndrome

A case report describes the case of a 54-year-old man with locked-in syndrome (LIS), a rare neurologic disorder in which patients can't move or speak but can otherwise think normally. It has been described as "being a prisoner in [your] own body." 

Historically, people with LIS have interacted with others by moving their eyes or blinking; nowadays, though, there are various assistive devices available and in development to help people communicate. The main cause of LIS is damage to a part of the brain called the ventral pons; the damage most commonly results from a stroke but can also be caused by trauma; infection; masses, such as tumors; or demyelinating disorders, such as multiple sclerosis. 

Patients can live for years with LIS. However, this patient had recurrent infections and died from pneumonia 36 days after being diagnosed with the condition.

If you miss your morning cup of joe, your temples may start throbbing. If you drink more than normal, that could cause a headache, too. And somehow, a strong cup of coffee can also stop some migraines in their tracks. 

So is caffeine the culprit or the cure for headaches? Is the problem too much or not enough? The answer: all of the above. 

The key to understanding caffeine is to remember that it's no ordinary ingredient. Caffeine is a psychoactive substance, said Dr. Richard Lipton, a professor of neurology at Albert Einstein College of Medicine in New York City. It has stimulating and vasoconstricting properties, meaning it speeds up brain activity and causes veins in the head to narrow, which help explain caffeine's roles in headaches — both as instigator and reliever. 

Related: Does coffee really give you an 'energy boost'? 

Caffeine as headache treatment 

Caffeine's ability to relieve a withdrawal headache or halt a migraine is well established; it's a key ingredient in multiple over-the-counter and prescription drugs, including headache-specific medicines like Excedrin. 

"It's not a pain reliever in its own right, but when combined with pain relievers, it makes them more effective," Lipton told Live Science. While caffeine's synergy with pain relievers is not fully understood, it could be related to caffeines activity in the brain.

The caffeine molecule binds to adenosine receptors in the brain and spinal cord. Normally, adenosine, a building block in DNA's molecular cousin RNA and in the main chemical fuel used by the body's cells, binds to these receptors, but it's blocked by ingested caffeine.  

By taking up the seats adenosine would normally occupy, caffeine blocks the molecules' effects. While adenosine slows nerve activity, caffeine increases it. Adenosine increases blood flow and causes blood vessels to widen, while caffeine constricts them; as some headaches partly stem from vasodilation in the head, caffeine's role as a vasoconstrictor may partly explain its effects. 

However, adenosine also plays a complex role in pain transmission, sometimes quelling pain signals and sometimes promoting them, so caffeine may also relieve headaches by messing with this signaling. Studies also show that, when taken with caffeine, pain relievers like acetaminophen are absorbed faster and their effects may last longer. In a study in which providers and patients didn't know whether they received an active pill or a placebo, caffeine with ibuprofen provided better and faster pain relief than ibuprofen alone.

However, caffeine's pain-killing abilities vary widely depending on how much people normally consume, according to Stanford Health Care. People develop a tolerance with frequent caffeine use and can then become dependent on caffeine's effects. This minimizes its headache-relieving effects. 

Related: What are the different types of headaches? 

Not enough or too much

On the flip side, caffeine can also cause headaches — both when people consume less than they normally would and when they consume too much. 

In the former case, headaches can occur because, with daily use, caffeine starts to change the brain's structure. "When your receptors are chronically exposed [to caffeine]," Lipton said, "then your brain doesn't function normally unless the caffeine is around."

Studies suggest that regular caffeine consumption increases the number of adenosine receptors in a person's brain, making a person more sensitive to adenosine's effects. Withdrawal headaches occur because the body becomes used to the vasoconstriction that comes with daily caffeine, and without it, those blood vessels suddenly swell, which can cause headaches. 

The good news is that once you catch up on your caffeine, these headaches usually go away — or after a period free from caffeine, the brain's number of adenosine receptors falls, as do the symptoms of withdrawal. 

Excess caffeine can also trigger headaches. Headache is one of the many side effects of caffeine overdose, and for some migraine patients, caffeine can actually trigger an attack. However, while there's rigorous evidence behind caffeine withdrawal headaches and caffeine's benefits in combination with painkillers, the reason excessive caffeine causes headaches is less established, Lipton said. But it's a phenomenon neurologists like Lipton have observed in the clinic, he said. 

To be safe, the Food and Drug Administration says healthy adults should limit their caffeine intake to 400 milligrams — the equivalent to four or five cups of coffee — per day.  But it's important to note that individuals' sensitivity to caffeine can vary. 

"Caffeine is definitely this two-edged sword," Lipton said. It can be mood-boosting and productivity-enhancing, and sometimes pain-stopping, but overuse and overdependence are fast paths to a throbbing headache. 

This article is for informational purposes only and is not meant to offer medical advice.

Many of us want (or should I say need?) our morning coffee to give us our "get up and go." Altogether, the people of the world drink more than two billion cups of coffee each day.

You might think coffee gives you the energy to get through the morning or the day  — but coffee might not be giving you as much as you think.

The main stimulant in coffee is the caffeine. And the main way caffeine works is by changing the way the cells in our brain interact with a compound called adenosine.

Getting busy, getting tired

Adenosine is part of the system that regulates our sleep and wake cycle and part of why high levels of activity lead to tiredness. As we go about our days and do things, levels of adenosine rise because it is released as a by-product as energy is used in our cells.

Eventually adenosine binds to its receptor (parts of cells that receive signals) which tells the cells to slow down, making us feel drowsy and sleepy. This is why you feel tired after a big day of activity. While we are sleeping, energy use drops lowering adenosine levels as it gets shuffled back into other forms. You wake up in the morning feeling refreshed. Well, if you get enough sleep that is.

If you are still feeling drowsy when you wake up caffeine can help, for a while. It works by binding to the adenosine receptor, which it can do because it is a similar shape. But it is not so similar that it triggers the drowsy slow-down signal like adenosine does. Instead it just fills the spots and stops the adenosine from binding there. This is what staves off the drowsy feeling.

No free ride

But there is a catch. While it feels energising, this little caffeine intervention is more a loan of the awake feeling, rather than a creation of any new energy.

This is because the caffeine won’t bind forever, and the adenosine that it blocks doesn't go away. So eventually the caffeine breaks down, lets go of the receptors and all that adenosine that has been waiting and building up latches on and the drowsy feeling comes back — sometimes all at once.

So, the debt you owe the caffeine always eventually needs to be repaid, and the only real way to repay it is to sleep.

Timing is everthing

How much free adenosine is in your system, that hasn't attached to receptors yet, and how drowsy you are as a consequence will impact how much the caffeine you drink wakes you up. So, the coffee you drink later in the day, when you have more drowsy signals your system may feel more powerful.

If it's too late in the day, caffeine can make it hard to fall asleep at bedtime. The "half life" of caffeine (how long it takes to break down half of it) is about five hours. That said, we all metabolise caffeine differently, so for some of us the effects wear off more quickly. Regular coffee drinkers might feel less of a caffeine "punch," with tolerance to the stimulant building up over time.

Caffeine can also raise levels of cortisol, a stress hormone that can make you feel more alert. This might mean caffeine feels more effective later in the morning, because you already have a natural rise in cortisol when you wake up. The impact of a coffee right out of bed might not seem as powerful for this reason.

If your caffeinated beverage of choice is also a sugary one, this can exacerbate the peak and crash feeling. Because while sugar does create actual energy in the body, the free sugars in your drink can cause a spike in blood sugar, which can then make you feel tired when the dip comes afterwards.

While there is no proven harm of drinking coffee on an empty stomach, coffee with or after a meal might hit you more slowly. This is because the food might slow down the rate at which the caffeine is absorbed.

Read more: Does coffee burn more fat during exercise? What the evidence tells us

What about a strong tea or fizzy cola?

Coffee, of course, isn't the only caffeinated beverage that can loan you some energy.

The caffeine in tea, energy drinks and other beverages still impacts the body in the same way. But, since the ingredients mostly come from plants, each caffeinated beverage has its own profile of additional compounds which can have their own stimulant effect, or can interact with caffeine to change its impacts.

Caffeine can be useful, but it isn't magic. To create energy and re-energise our bodies we need enough food, water and sleep.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Veterinarians frown upon giving dogs any kind of "people food" but are especially adamant about keeping chocolate far away from our canine friends. During holidays such as Easter, when delicious chocolate may be more commonly found around the house, it's even more important to be vigilant about your pet gulping down this human treat. 

But why is chocolate — milk or dark — so toxic for dogs?

Chocolate contains the chemicals theobromine and caffeine, and these two stimulants — which dogs can't metabolize as easily as people can — accumulate in the animal's body, where they can rev up a dog's bodily functions and cause dangerous side effects, according to VCA Animal Hospitals. 

The severity of chocolate's negative impacts on a dog are determined by the levels of theobromine and caffeine in the chocolate product, how much of it the dog ate, and the dog's weight and sensitivity to chemical stimulants. Chocolate that is dark and bitter is more toxic to dogs, as it contains a higher concentration of theobromine per ounce than milk chocolate (130 to 450 milligrams per ounce, compared with milk chocolate's 45 to 58 mg per ounce). White chocolate, on the other hand, contains just 0.25 mg of theobromine per ounce, and therefore poses a much lower toxic threat to dogs, according to VCA Animal Hospitals.

What are symptoms of chocolate toxicity in dogs?

Initial symptoms of chocolate toxicity typically appear within 6 to 12 hours, and may include excessive drooling and panting, increased thirst and urination, and an upset stomach followed by vomiting and diarrhea, according to the American Kennel Club (AKC). The dog may experience an increased heart rate and become restless, nervous and excited, much like a caffeine-sensitive person who has downed too many cups of coffee. 

In severe cases, irregular heart rate from chocolate consumption can reduce circulation, resulting in a drop in body temperature. Extreme symptoms include lethargy, muscle spasms, seizures and coma, sometimes leading to death, according to VCA Animal Hospitals. And because theobromine has a long half-life, which means it takes longer for the body to break it down, symptoms of chocolate poisoning can persist for days.

In some cases, dogs consume chocolate but show no symptoms; that's because the dosage size of the toxins can affect an animal's response to being poisoned, according to the Office for Science and Society at McGill University in Ontario, Canada.

How do veterinarians treat chocolate poisoning?

Veterinarians typically treat chocolate toxicity by inducing vomiting or administering doses of activated charcoal,  which purges toxins from the dog's digestive system before they can be absorbed by the animal's bloodstream, according to the AKC. Depending on the severity of the poisoning, medication or fluids may be required to counteract the poisoning, the AKC says.

What might affect a dog's reaction to chocolate?

How a dog reacts to chocolate can depend on the animal's size, said veterinarian Dr. Greg Nelson, Director of Surgery and Director of Diagnostic Imaging at Central Veterinary Associates in Valley Stream, New York. A square of chocolate will therefore have a more pronounced effect on a Chihuahua, which typically weighs about 4 to 6 pounds (1.8 to 2.7 kilograms) than on a Saint Bernard, which can weigh as much as 180 pounds (81.6 kg).

"One hundred milligrams of theobromine and caffeine per each kilogram of a dog's weight is enough to be lethal," Nelson told Live Science. (A kilogram equals 2.2 pounds.) "Different chocolate products have varying levels of theobromine and caffeine, and the worst offender is baker's chocolate. In my experience, one ounce of baker's chocolate per kilogram [of the dog's body weight] can be lethal."

Milk chocolate is less dangerous than baking chocolate because it contains less stimulants, but Nelson warns that if your dog has ingested any type or amount of chocolate, you are always better off being safe than sorry.

"I advise clients to come in instead of second-guessing and possibly creating an emergency by not having the dog looked at right away," Nelson said. "At the very least, call your veterinarian or the national Animal Poison Control center for advice." (The American Society for the Prevention of Cruelty to Animals (ASPCA) Animal Poison Control Center can be reached 365 days a year at 888- 426-4435.)

While chocolate poisoning may affect dogs at any time, pups are more likely to find and consume chocolate on holidays such as Christmas and Easter when plentiful chocolate is available as figurines (such as bunnies and Santa Claus), as well as in bars, eggs, liqueurs, cakes and decorations, researchers wrote in a 2017 paper in the journal Vet Record. In fact, during Christmastime, dogs are four times more likely to require a vet visit for chocolate poisoning than during non-holidays; and on Easter, dogs are twice as likely to be sickened by chocolate, compared with other times of the year, Live Science previously reported.

Additional resources

Read more from the ASPCA on their Toxicology and Poison Control web page, to learn about toxins, medications, hazards and resources that could help you save the life of your pet in the event of a toxic exposure. The Veterinary Emergency Group provides tips for identifying symptoms of chocolate toxicity in dogs, and recommends what to do in an emergency. The ASPCA also compiled a list of other human foods that are hazardous for pets to eat, such as avocados, coconuts, citrus and alcohol, among others.

This article is for informational purposes only, and is not meant to offer medical advice.

Originally published on Live Science.

Bibliography

"Chocolate Poisoning in Dogs." Chocolate Poisoning In Dogs | VCA Animal Hospitals, https://vcahospitals.com/know-your-pet/chocolate-poisoning-in-dogs. 

Staff, AKC. "What to Do If Your Dog Eats Chocolate." American Kennel Club, American Kennel Club, 28 Dec. 2021, https://www.akc.org/expert-advice/health/what-to-do-if-your-dog-ate-chocolate/. 

"My Dog Ate Chocolate and He Was Fine, so What's the Big Deal?" Office for Science and Society, 26 Aug. 2019, https://www.mcgill.ca/oss/article/health/my-dog-ate-chocolate-and-he-was-fine-so-whats-big-deal. 

Noble, Peter-John M, et al. "Heightened Risk of Canine Chocolate Exposure at Christmas and Easter." Veterinary Record, vol. 181, no. 25, 2017, pp. 684–684., https://doi.org/10.1136/vr.104762. 

"Toxicology & Poison Control." ASPCApro, 21 Mar. 2022, https://www.aspcapro.org/topics-animal-health/toxicology-poison-control. 

"Chocolate Toxicity in Dogs: Signs and What to Do." Veterinary Emergency Group, 21 Feb. 2022, https://veterinaryemergencygroup.com/blog/chocolate-toxicity-in-dogs/. 

"People Foods to Avoid Feeding Your Pets." ASPCA, https://www.aspca.org/pet-care/animal-poison-control/people-foods-avoid-feeding-your-pets. 

A man in the U.K. died from a caffeine overdose after drinking a mixture containing the caffeine equivalent of several hundred cups of coffee, according to news reports.

The 29-year-old man, Tom Mansfield, was a personal trainer who had ordered a 100 gram (3.5 oz) bag of caffeine powder to use in supplement drinks, according to Yahoo News. However, when measuring the powder on a scale, he made an error that resulted in him consuming a fatal dose of caffeine.

The recommended dose of caffeine powder was between 60 and 300 milligrams (0.002 and 0.01 oz), but the scale Mansfield used had a starting weight of 2 grams (0.07 oz), according to the BBC. This meant Mansfield ended up consuming several grams of the powder, equivalent to up to 200 cups of coffee, according to the BBC.

Related: 10 things you need to know about coffee

Immediately after consuming the drink on Jan. 5, 2021, Mansfield clutched his chest and said his heart was beating fast, the BBC reported. He then began foaming at the mouth, and his wife called an ambulance. Mansfield was taken to the hospital after going into cardiac arrest, and was pronounced dead later that day.

The coroner found that Mansfield had a caffeine level in his blood of 392 mg per liter. The typical caffeine level after drinking a cup of coffee is around 2 to 4 mg per liter, the BBC reported.

Caffeine powders can be dangerous because they are much more potent than caffeine-containing beverages like coffee. In 2015, the U.S. Food and Drug Administration warned several companies selling the powder that their products posed a "significant or unreasonable risk of illness or injury to consumers," Live Science previously reported.

The agency noted that it can be difficult for consumers to accurately measure a safe dose of caffeine powder. For example, to measure out 50 mg of powder using a quarter-teaspoon measuring spoon, a consumer needs to fill just 6% of the spoon. "The difference between a safe amount and a toxic dose of caffeine in these pure powdered products is very small," the agency said.

In Mansfield's case, the company that sold the powdered caffeine product did not include a scoop to measure at the time of Mansfield's death; but the brand now does include a scoop, according to North Wales Live. The corner said that if the scoop had been available at the time, Mansfield would likely still be alive, North Wales Live reported.

Related: signs you might have caffeine sensitivity

Originally published on Live Science. 

A young man's heart problems may have been triggered by his excessive consumption of energy drinks — he ended up in the hospital with heart failure after consuming four energy drinks per day for two years, according to a new report of the case.

The findings add to a growing body of evidence linking energy drink consumption with heart problems, leading the authors to call for warnings about the dangers of drinking these beverages in large amounts.

The 21-year-old man went to the hospital after he experienced progressively worse shortness of breath for four months as well as weight loss, according to the report, published Thursday (April 15) in the journal BMJ Case Reports.

Related: 10 interesting facts about caffeine

He reported drinking four 500-milliliter cans of energy drinks every day for about two years, with each can containing 160 milligrams of caffeine. (A typical cup of coffee contains about 90 mg of caffeine.)

The man recalled that he occasionally had episodes of indigestion, tremors and a racing heartbeat, which he didn't seek care for in the past. He felt so unwell and lethargic in recent months that he had to stop his university studies, according to the report, from doctors at St Thomas' Hospital in London.

After a barrage of tests, the man was diagnosed with two potentially life-threatening conditions: heart failure and kidney failure. Heart failure occurs when the heart muscle can't pump enough blood to meet the body's needs; and kidney failure happens when the kidneys can't properly filter waste products from the blood. In the man's case, the two conditions appeared to be unrelated, but they each had serious effects. The man's doctors discussed whether he needed a double (heart and kidney) organ transplant. 

His kidney failure was due to a long-standing but previously undiagnosed condition called chronic obstructive uropathy, when urine can't properly drain through the urinary tract tubes and so it backs up into the kidneys.

His doctors considered a number of possible causes for his heart failure, including "broken heart syndrome," when the heart's main pumping chamber becomes enlarged and weakened, and myocarditis, or inflammation of the heart. However, neither condition fit with the man's history and test results. The most likely explanation for his heart failure was his high level of energy drink consumption, the authors concluded, although they can't prove this for certain.

Previous studies have linked energy drink consumption with concerning cardiovascular effects, including increased blood pressure and abnormal heart rhythms. There have been several reports of young people who have suffered heart attacks and heart rhythm problems after consuming energy drinks, Live Science previously reported.

After 58 days in the hospital, the man was cleared to go home and was prescribed several heart medications. He stopped drinking energy drinks completely and his heart function improved so much that his doctors say he doesn't need a heart transplant at this time. However, he will likely need a kidney transplant at some point in the future.

Some people may be predisposed to heart problems from energy drinks due to underlying biological factors, although more research is needed to determine what these factors are, the authors said.

"This case further highlights the potential cardiovascular dangers of energy drinks in susceptible individuals," the authors wrote. "Clear warnings should be provided about the potential cardiovascular dangers of energy drink consumption in large amounts," they concluded.

Originally published on Live Science.  

One reason coffee isn't usually given to kids may be the widely held belief that the caffeinated beverage can stunt children's growth. But is there any truth to this idea?

The answer is a resounding "no": There's no evidence that coffee or caffeine stunts childhood growth and development. 

Instead, a person's height is largely governed by other factors. For example, hundreds of genes so far identified are thought to be responsible for approximately 16% of a person's adult height. 

Related: Can carrots give you night vision?

A child's general health also plays a role. For example, repeated infection during infancy can slow nutritional uptake and bone growth, as shown by a number of different studies. Moreover, whether a child has access to important dietary needs, such as milk, during their early years also influences height, as does the mother's diet during pregnancy, according to research in the journal Nutrition Research Reviews. 

So, why do some people still believe that coffee can stunt a child's growth? 

No one really knows, but there are a couple of theories. In the 1980s, several studies suggested that regular coffee drinkers were at an increased risk of osteoporosis because caffeine can lead to increased calcium excretion (although the effect was small). If caffeine was capable of weakening bones then it was conceivable that higher consumption in childhood would lead to shorter stature. However, it turned out that there was another variable at play: Coffee drinkers also tended to consume less milk, a major source of calcium. In other words, it likely was not the coffee, but rather the insufficient calcium, causing the problem. Moreover, later research has found no link between osteoporosis and coffee consumption, according to Harvard Health Publishing.

Another idea is that many studies have linked caffeine consumption with both positive and negative health effects, only contributing to the confusion.

"There have been so many epidemiological studies of coffee, indicating harm or good, that it is confusing," said science writer Mark Pendergast, author of "Uncommon Grounds: The History of Coffee and How It Transformed Our World" (Basic Books, 2019). 

Related: Signs you might have caffeine sensitivity

Another theory, favored by Duane Mellor a dietitian at Aston University in the United Kingdom, is that the myth stems from the recommendation that pregnant women limit their caffeine consumption because some research has linked a fetus's exposure to caffeine with a higher risk of spontaneous miscarriage. These studies, however, are limited by small sample sizes. The evidence is inconclusive at the moment, so health groups such as the World Health Organization now advise pregnant women to limit (but not necessarily completely avoid) caffeine consumption to reduce the possible risk of pregnancy loss and low birth weight in infants.

"That's where we've got this idea of growth and caffeine, but the biology of a fetus and how it gets its nutrients pushed through a placenta is so different from a free-living individual," Mellor said. "The metabolisms are different, too. You can't draw parallels." 

Related: Does sugar make kids hyper?

So, the science is clear: Coffee doesn't stunt kids' growth. In fact, it's probably healthier for your child to quaff a weak cup of joe than a sugary, tooth-rotting soda, said Mellor. 

"A weak coffee probably isn't a big deal," Mellor told Live Science. "Some of the bitter notes in coffees are shared by vegetables, and you might even see a benefit in getting them [kids] used to those flavors. Obviously, you wouldn't want to give them a strong coffee, but really I'd be more concerned about sweet drinks." 

But Mellor doesn't advise giving your toddler a double espresso every morning, either. And for good reason: Moderation is key. Caffeine can cause increased anxiety, high blood pressure and acid reflux, and it can also interfere with sleep, according to Johns Hopkins Medicine. Caffeine from coffee can also cause these issues in adults, of course. But children have smaller bodies, so the same amounts of caffeine can have more pronounced effects in them, also according to Johns Hopkins Medicine. For that reason, the American Academy of Pediatrics recommends young children abstain and adolescents limit their coffee drinking. 

Despite the evidence, this coffee myth likely isn't going away anytime soon.

"The widespread myth that it stunts your growth isn't going to completely die out," Pendergast told Live Science. "Once a health myth enters our culture, it is very difficult to eradicate it." 

Originally published on Live Science.

Drinking too much coffee or other caffeinated drinks may be a trigger for migraines among people prone to these severe headaches, a new study suggests.

The study researchers found that, among people with periodic migraine headaches, consuming at least three caffeinated drinks a day was tied to a higher likelihood of experiencing a migraine on that day or the following day. However, consuming only one or two caffeinated drinks a day was generally not associated with migraines, the study found.

Although many people anecdotally report that caffeine tends to trigger their migraines, few rigorous studies have examined this link. Indeed, the new study, published today (Aug. 8) in The American Journal of Medicine, is one of the first to examine whether daily changes in caffeine intake are tied to the onset of migraines. [Ouch: 10 Odd Causes of Headaches]

"Interestingly, despite some patients with episodic migraine thinking they need to avoid caffeine, we found that drinking one to two servings [per] day was not associated with higher risk of headache," study senior author Dr. Suzanne Bertisch, an assistant professor at Harvard Medical School and a clinical investigator in the Division of Sleep and Circadian Disorders at Brigham and Women's Hospital in Boston, said in a statement. Still, more research is needed to confirm the findings; "but it is an important first step," Bertisch said.

The role of caffeine in triggering migraine headaches may be particularly complex, the authors said, because its impact depends on how much people consume and how often. Caffeine may trigger an attack, but it could also have a pain-relieving effect, they said.

In the new study, the researchers analyzed information from nearly 100 adults who were diagnosed with episodic migraines, which means they experienced migraine headaches at least twice a month, but no more than 15 times a month. (People with 15 or more migraine headaches per month have a condition called "chronic migraine.")

Participants filled out an online survey twice a day for six weeks to record their caffeine intake — including the number of servings of coffee, tea, soda and energy drinks they consumed — and whether they experienced a migraine headache that day.

On average, participants reported experiencing about eight migraines during the six-week study period. All of the participants reported consuming caffeine at least once during the study period, and on average, they consumed about eight servings per week.

For each participant, the researchers compared reports of migraines on the days they consumed caffeine with reports of migraines on the days they did not consume caffeine.

Overall, participants were more likely to experience migraine headaches on days they consumed three or more caffeinated beverages, compared with days they didn't consume caffeinated beverages. But there wasn't a link between migraine headache and consumption of one or two caffeinated beverages.

However, among people who rarely consumed any caffeine, even one to two servings of caffeine increased the chances of having a headache on that day, the authors said.

The findings held even after the researchers took into account other factors that could trigger migraines, including alcohol consumption, stress, exercise and sleep deprivation.

It's possible that some participants tended to consume caffeinated drinks after their migraines started. To try to rule out such "reverse causation," the researchers examined the link between caffeine consumption on a given day and migraine headaches on the following day. Their findings were similar: Drinking at least three caffeinated beverages was linked with an increased risk of migraine on the following day.

Still, the study was not able to examine whether factors such as the type of caffeinated beverages, total amount of caffeine or time of day of consumption affected the risk of migraines, and so more research is needed to investigate this, the authors said.

•  10 Things You Need to Know About Coffee 
•  11 Ways Processed Food Is Different from Real Food 
•  9 Snack Foods: Healthy or Not? 

Originally published on Live Science.

The story of decaf coffee starts, improbably, with Johann Wolfgang von Goethe.

Goethe, who wrote the tragedy "Faust," was one of Germany's most famous authors, but he also dabbled in natural science. In 1819, Goethe saw the chemist Friedlieb Ferdinand Runge demonstrate how deadly nightshade extract could dilate a cat's pupils. Impressed, Goethe gave Runge a small box of coffee beans from Greece and tasked the chemist with figuring out why the stuff kept him up at night.

A couple of years later, Runge became the first scientist to isolate and identify caffeine. (Those who are extra-sensitive to the jittery effects of a cup of strong coffee probably won't be surprised to hear that the discoverer of the stimulant had a penchant for working with deadly substances; his colleagues and students allegedly nicknamed him "Doktor Gift," which means "Dr. Poison" in German.) [Does Medicine Really Expire?] 

According to the Max Planck Institute, it took almost another 100 years after Runge's discovery before scientists figured out how to extract caffeine from coffee and still have a beverage that tasted somewhat like the real thing. 

Chemical solvents, CO2 and water

Today, decaffeination is an intensive process that takes place at specialized facilities.

"There are a couple [of] very large [coffee] companies that own their own decaf plants, but beyond that every other company either contracts directly with a decaffeination company or they contract through an importer," David Kastle, a senior vice president at the Canada-based company Swiss Water Decaffeinated Coffee, told Live Science.

Generally, decaffeination involves water-logging coffee beans when they're still green (before roasting) so that the caffeine inside can be made soluble, meaning that it can be dissolved. But there are different ways of washing that caffeine out of the beans.

The first commercially successful decaffeination method was invented around 1905, by German coffee merchant Ludwig Roselius. According to Atlas Obscura, one bit of lore about the origins of decaf claims that Roselius received a shipment of coffee beans that was soaked in seawater. Instead of tossing the beans, Roselius decided to process and test them. He found that the coffee had been stripped of its caffeine content but still basically tasted like coffee, albeit a bit salty.

Roselius then figured out he could use benzene — a chemical that, at the time, was also used in paint strippers and aftershave — as a solvent to remove caffeine from coffee beans. His company, Kaffee HAG, was the first to produce instant decaf coffee. The coffee was sold as "Sanka" in the United States by General Foods, and was a mid-20th-century staple — and occasional punchline. (In the 1982 movie "Fast Times at Ridgemont High," a biology teacher pleads with his students, "I'm a little slow today. I just switched to Sanka, so have a heart.")

Benzene is no longer used for decaffeinating coffee because it's a known carcinogen. Instead, companies that use chemical solvents have switched to other substances, predominantly ethyl acetate and methylene chloride, although there has been some controversy about the latter because exposure to high amounts of the substance can be toxic and lead to damage of the central nervous system. The FDA has ruled that miniscule trace amounts of methylene chloride in decaf coffee are not cause for concern, and residues of more than 0.001% are prohibited.

Another method for decaffeinating coffee also originated, somewhat accidentally, in Germany. Chemist Kurt Zosel was working with supercritical carbon dioxide at the Max Planck Institute for Coal Research in Ruhr. Zosel discovered that when the gas is heated and put under a lot of pressure, it enters a supercritical state that can be useful for separating different chemical substances — including separating caffeine from coffee when it's pumped through the beans.

The chemist patented his decaffeination method in 1970; it's still widely used today. According to NPR, crude caffeine can be salvaged during the supercritical carbon dioxide decaffeination process, which is used in sodas, energy drinks and other products.

Yet another method, dubbed the Swiss Water Process, was first used commercially in the 1970s. Kastle explained that first, a batch of green coffee beans is soaked in water. That water becomes saturated with all the soluble components found in coffee — including chlorogenic acid, amino acids and sucrose; the caffeine is then filtered out with carbon. This uncaffeinated liquid, called green coffee extract, is then added to columns of new, rehydrated, green coffee beans that still have their caffeine. Kastle said that caffeine migrates from the beans to the green coffee extract as the beans and liquid seek equilibrium, until the beans are almost entirely caffeine-free.

According to Consumer Reports, it can be difficult to figure out the process by which your decaf coffee has been made; there are no specific labeling rules that require companies to disclose this information. Some coffee companies do, however, advertise their methods. (The high-end coffee company Blue Bottle, for instance, flaunts its use of the Swiss Water Process in making its decaf.)

And the FDA says that decaffeinated coffee might still contain small amounts of caffeine, warning consumers that an 8-ounce cup of decaf typically has 2 to 15 milligrams of caffeine. But that's still much lower than a caffeinated cup of joe; for comparison, the same amount of regular coffee usually has about 80 to 100 mg of caffeine.

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Originally published on Live Science.

It may sound counterintuitive, but people who are supersensitive to coffee's bitter taste actually drink more of it, a new study finds.

This sensitivity isn't simply a matter of taste, either, but rather is influenced by a person's genetic makeup, the researchers said in the study, which was published online today (Nov. 15) in the journal Scientific Reports.

"You'd expect that people who are particularly sensitive to the bitter taste of caffeine would drink less coffee," study senior researcher Marilyn Cornelis, an assistant professor of preventive medicine at the Northwestern University Feinberg School of Medicine in Chicago, said in a statement. "The opposite results of our study suggest coffee consumers acquire a taste [for] or an ability to detect [the bitterness of] caffeine due to the learned positive reinforcement elicited by caffeine." [10 Things You Need to Know About Coffee]

Put another way, people who have a heightened ability to taste the bitterness of coffee, and especially the distinct bitter flavor of caffeine, learn to associate "good things with it," Cornelis said. This finding is surprising, given that bitterness often serves as a warning mechanism to convince people to spit out harmful substances, the scientists said.

Researchers conducted the study to understand how genetics influences people's consumption of tea, coffee and alcohol, which tend to taste bitter, said lead study researcher Jue Sheng Ong, a doctoral student in the Department of Genetics and Computational Biology at the QIMR Berghofer Medical Research Institute in Brisbane, Australia.

"While all bitter flavors might seem the same, we perceive the bitterness of Brussels sprouts, tonic water (quinine) and caffeine separately," Ong told Live Science. "The degree to which we find these flavors bitter is, in part, determined by your genes."

To investigate, the researchers looked at the genetic makeup and daily bitter-beverage consumption of more than 400,000 people from the United Kingdom. "Using the genes related to our ability to taste bitterness, we were able to assess whether those that have a higher genetic predisposition to tasting bitterness are more likely to prefer tea over coffee," Ong said.

The results showed that people with the genes to taste the bitterness of green vegetables (such as Brussels sprouts) or tonic water are more likely to prefer tea over coffee, the researchers found. In addition, people who were more sensitive to quinine's bitter flavors and those found in green vegetables tended to avoid coffee.

Meanwhile, people with the genes to taste the bitterness in Brussel sprouts were less likely to drink alcohol, especially red wine, than people without those gene variants, the researchers found. This insight may help scientists studying addiction, Ong said.

Ong noted that the researchers didn't look at flavorings, such as cream or sugar, that people sometimes pour into coffee to temper its bitterness. "One can imagine that, at a personal level, there are a lot of factors that determine a person’s coffee intake — socioeconomic status, ability to metabolize caffeine and smoking," he said. "On top of that, people drink all sorts of coffee — black coffee, flat white [and] cappuccino." So, the researchers chose to look for big trends in how genes relate to bitter-beverage consumption, he said.

"[The results] suggest that perhaps most types of coffee still share very similar bitter-taste profiles," Ong said.

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Originally published on Live Science.

Some diet supplements that contain caffeine claim that the compound helps reduce appetite. Other research has suggested that caffeine could speed up metabolism.

It looks like those claims don't live up to the hype: According to a new study published today (July 19) in the Journal of the Academy of Nutrition and Dietetics, caffeine doesn't have an effect on weight loss.

In the study, researchers recruited 50 healthy adults between the ages of 18 and 50, and one day a week for three weeks, asked them to come to the lab in the morning to drink either some caffeine-infused juice or a placebo. The drink either contained no caffeine, caffeine equivalent to a 4-ounce serving or caffeine equal to an 8-ounce coffee. The participants weren't told which drink they received each time, but by the end of the experiment, they had each received all three of the drinks. [10 Interesting Facts About Caffeine]

Thirty minutes after drinking the juice, the participants were presented with a breakfast buffet, where they were allowed to eat as much as they wanted. Then, they were sent home and instructed to document everything they ate throughout the rest of the day using an online tool. They also recorded their appetite levels throughout the day.

The researchers found that when people were given the lower-dose caffeine drink, they ate around 10 percent less at the breakfast buffet, on average, than when they were given the caffeine-free drink or the higher-dose drink. After drinking the low-dose beverage, the participants ate around 650 calories, on average, at the breakfast buffet; after consuming the caffeine-free beverage, they ate 721 calories, on average; and after having the high-dose drink, they ate 715 calories, on average. No one's reported appetite for breakfast seemed to change based on how much caffeine they had.

Outside of the lab, the researchers found no significant differences in participants' appetites or the amounts of food eaten throughout the day based on the amount of caffeine they drank. They also found that the participants' body-mass indexes had no effect on their appetite or how much they ate.

The findings — that caffeine may have a small effect on food intake shortly after drinking it but the effect quickly wears off — "suggest caffeine has weak, transient effects on energy intake and do not support caffeine as an effective appetite suppressant," the authors wrote in the study.

Instead, the study "reinforces the importance of good eating habits and not relying on unsupported weight loss aids or unhealthy practices," study co-author Carol DeNysschen, chair of the Department of Health, Nutrition, and Dietetics at SUNY Buffalo State College, said in a statement.

Originally published on Live Science.

A new report divides coffee lovers into three groups depending on how their bodies respond to caffeine.

But as fun as it is for caffeine drinkers to figure out which group they fall into, not all experts are on board with the report's clear-cut conclusions.

According to the report, which was published June 6 by the Institute for Scientific Information on Coffee (ISIC), the answer lies in our genes. Specifically, caffeine sensitivity depends partly on a liver enzyme called CYP1A2, which is coded by the CYP1A2 gene. The enzyme is responsible for "inactivating 95 percent of all ingested caffeine," the report said. In other words, this liver enzyme breaks down caffeine in the body. [10 Interesting Facts About Caffeine]

ISIC members include several European coffee companies, including Nestlé.

The versions of the gene vary among people, according to the report, and these genetic variations split the population into two groups: "fast metabolizers" and "slow metabolizers." The fast group breaks down caffeine more quickly than the slow group, and thus the effects of caffeine don't last as long for this group, the report says.

J.W. Langer, a clinical pharmacology lecturer at the University of Copenhagen and the author of the report, claims that these fast metabolizers can drink "multiple cups of coffee a day" because their bodies can quickly clear caffeine from their systems. But for slow metabolizers, caffeine stays in the body longer, so "the physiological effects of caffeine last longer and are more pronounced," Langer said. Thus, the report recommends lower doses of caffeine for this group.

But where did the third group come from?

"You have the genes for the liver enzymes, but you also have to consider how coffee affects the brain," Langer told Live Science.

That’s where adenosine, a neurotransmitter, comes in. Adenosine binds to adenosine receptors, leading to the sensation of being tired. But caffeine can also bind to these receptors, blocking the adenosine from binding and, in turn, preventing tiredness and boosting alertness.

Related: Does Caffeine Sensitivity Increase With Age?

As with the liver enzyme responsible for breaking down caffeine, there are also genetic variations in the genes that produce the adenosine receptor, according to the report. These variations, along with variations in the enzymes, "combine to factor into the three caffeine sensitivity groups: high, regular and low," Langer said. (The low-sensitivity group includes the "fast metabolizers" while the high-sensitivity group includes the "slow metabolizers.")

The report says that, because individuals tend to consume "the amount of caffeine they feel comfortable with," their levels of consumption are based on "self-regulating mechanisms rooted in the individual's genetic make-up." In turn, the report advises those with high sensitivity to consume caffeine in small amounts and says those with regular sensitivity will be "safe and without problems" with a "moderate caffeine consumption of 5 cups a day." (It's unclear, however, if the report was referring specifically to 8 ounces of coffee as a cup, or a more colloquial definition; in Europe, coffee is typically served in smaller cups than it is in the U.S.)

Caffeine concerns remain

But the new report has not been fully accepted by the scientific community. Nanci Guest, a dietitian and researcher at the University of Toronto who was not involved with the new report, said it's largely misleading. [10 Things You Need to Know About Coffee]

"The gist of this report is that you drink as much coffee as you feel comfortable with, and you'll be OK," Guest told Live Science. "That take-home message is not based in any real evidence, and this report freely promotes coffee intake without considering any of the risks."

According to Guest, the term "sensitivity" is not an accurate description because it assumes that individuals can "feel the effects of caffeine intake," including the possibility of "increased heart attack risk, high blood pressure and decreased endurance performance."

Langer, however, said that he defines sensitivity as "what you feel when you drink coffee," and hopes that this report will help people recognize that "everyone is a unique coffee drinker."

He also cautioned against drinking excessive amounts of coffee to achieve the effects of caffeine, stating that although "low sensitivity" individuals may need more caffeine to feel the effects, there are potential negative effects.

These negative effects include mainly "anxiety and panic attacks," particularly if you’re sensitive to caffeine, Langer said, but these sensitive individuals are in "the minority."

Guest emphasized that "the jitters" are just the tip of the iceberg when it comes to the negative effects of caffeine.

She also noted that there are inaccuracies in the report and that the advice given should be taken with a grain of salt. For example, while the report states that pregnant women should limit their caffeine intake to 200 milligrams (mg), Guest said zero caffeine intake is the safest. (The American College of Obstetricians and Gynecologists, however, supports the 200-mg. limit.)

Guest also refuted the "moderate" five cups of coffee a day, stating that such levels of intake should be considered carefully.

Moreover, while the report states that coffee consumption has possible preventive effects against Parkinson's disease, these reports have been disputed recently, Guest said.

Originally published on Live Science.

Many people groggily pour a cup of coffee in the morning to wake themselves up. But exactly how much caffeine should you consume — and when should you take it — to achieve "peak" alertness?

A new algorithm aims to answer that question.

The algorithm, developed by U.S. Army researchers, takes into account people's sleep schedules and identifies how much caffeine they should consume, and when, to achieve optimal alertness. [10 Interesting Facts About Caffeine]

The researchers found that, by using this algorithm, they could improve people's performance on an attention task by up to 64 percent, even though people were consuming the same total amount of caffeine as they did before. (The algorithm may recommend, for example, a specific amount of caffeine at one time, and then a different amount later in the day.) The study also found that, by following the algorithm's dosing schedule, people could reduce their caffeine consumption by up to 65 percent, and still achieve the same level of performance.

"We developed algorithms that work together, and they essentially allow us to determine, at the individual level, when and how much the individual should take caffeine to achieve peak performance at the desired time, for the desired duration," said study senior author Jaques Reifman, director of the DoD Biotechnology High Performance Computing Software Applications Institute at the U.S. Army Medical Research and Materiel Command in Fort Detrick, Maryland. 

For example, if you're a student who has been sleep-deprived for the last week while cramming for an upcoming exam, the algorithm aims to tell you when to take caffeine "so you are as alert as possible during the exam," Reifman told Live Science.

The researchers have already used their technology to develop a web-based tool and a smartphone app, called 2B‐Alert, which can predict a person's alertness based on their sleep time and caffeine consumption. The web tool provides a result for the "average Joe," while the smartphone app learns over time how an individual responds to sleep deprivation and caffeine, Reifman said.  

Currently, the publicly available version of 2B-Alert doesn't tell people when and how much caffeine to take to achieve peak performance. This aspect of the work is still being validated in studies on U.S. soldiers.

Ultimately, although the work is being developed for the military, Reifman hopes it can also benefit the lay public, including shift workers, air traffic controllers and even students cramming for a test. "We all suffer from sleep deprivation" from time to time, Reifman said.

The study was published May 28 in the Journal of Sleep Research.

Caffeine and timing

The effectiveness of caffeine depends not just on how much you consume, but when you consume it — for a sleep-deprived person, a single cup of coffee in the morning may not prevent drowsiness later in the day.

Previously, the researchers developed a mathematical model, called the unified model of performance (UMP), which could predict the effects of sleep loss and caffeine consumption on a person's performance. But this model didn't tell people exactly when and how much caffeine they needed to take to achieve their peak performance.

To address this issue, the researchers combined the UMP with an "optimization algorithm." The new algorithm used a person's sleep schedule as the input and provided a "caffeine-dosing strategy" (when and how much caffeine to take) as the output.

The researchers then tested their algorithm using data from previous studies on the effectiveness of caffeine on people who were sleep-deprived. In these earlier studies, people were deprived of sleep for certain amounts of time and given specific doses of caffeine. Then, the researchers measured how well the caffeine improved their performance on a simple task that measured attention and reaction time.

In the new study, the researchers ran computer simulations to examine people's performance using the caffeine dosing strategies in the original studies, as well as the dosing strategies determined by the new algorithm.

They found that the dosing strategies from the new algorithm could improve people's performance by 16 to 64 percent and reduce total caffeine consumption by 17 to 65 percent, compared with the earlier studies.

How was this possible? For example, in one study, participants consumed 400 milligrams of caffeine at the same time each day, for five days, for a total of 2,000 mg. But because the participants were sleep-deprived — getting just 5 hours of sleep a night — they gradually accumulated a "sleep debt" that hurt their performance, particularly later in the day. So the optimization algorithm determined that participants needed more caffeine later in the week (particularly later in the day) — and less caffeine at the beginning of the week — to optimize their performance.

While the current study was retrospective (meaning it used previous data), the researchers are planning another study that will test the algorithm in real time. In this future study, soldiers will be deprived of sleep for a certain amount of time. About halfway through this period, the algorithm will determine how much caffeine each solider needs, and at what time, so that they achieve at least a certain level of alertness, Reifman said.

Reifman said the optimization algorithm should be available on the 2B-Alert platform sometime before the end of the year.

Original article on Live Science.

A standard cup of coffee contains around 100 milligrams of caffeine; a Red Bull has 80 mg. But according to the Center for Science in the Public Interest, one caffeinated beverage manages to pack around 200 mg of caffeine into less than 2 fluid ounces (56 milliliters): 5-hour Energy. 

So, what would happen if you were to drink five 5-hour Energy shots at once? Would you gain 25 hours of energy? Or would the consequences be more severe?

The answer to what would happen is, "nothing good," said Kathleen Miller, an energy-drink specialist at the University at Buffalo Research Institute on Addictions. Five bottles of 5-hour Energy contain about 1,000 mg of caffeine — the equivalent of the caffeine in 10 cups of coffee. [Does Caffeine Really Dehydrate You?]

"Caffeine can be a great thing, at low doses," Miller told Live Science. "With the consumption of five 5-hour Energy drinks, however, you move past alert and awake, into the territory of jittery, anxious and [heart palpitations]."

True caffeine intoxication doesn't kick in, however, until you reach even higher doses: 5,000 mg of caffeine, or the amount in 50 cups of coffee and 25 5-hour Energy drinks. At these levels, a person will experience the more life-threatening effects of caffeine, including "seizures, strokes [and] hallucinations," Miller said. And yes, caffeine can be deadly at these extreme doses, she added.

In 2012, an Amazon user posted a reviewfor 5-hour Energy after claiming to drink 22 5-hour Energy drinks poured into a Super Big Gulp cup. In a list of cons, the user stated that they "hadn't slept in 72 hours" and that they couldn't feel their own pulse. As a positive, the user joked that they could now read minds.

While such extreme circumstances are rare, Miller emphasized that the risk of caffeine intoxication is higher in people with existing heart conditions. In 2012, for example, a 14-year-old girl with a heart valve problem diedafter drinking two 24-ounce Monster Energy drinks in 24 hours — together they contained 480 mg of caffeine.

Excessive caffeine consumption is also especially dangerous for children and teenagers with "low body mass," Miller said.

"Chemically, caffeine can deceive your body into thinking it's wide awake when what you really need is sleep," she noted. "This is harmful for young people who need sleep, and for everyone long-term. With repeated use, caffeine can elevate blood pressure and cause prolonged sleep disturbances."

In addition, there are certain plant and herbal extracts in energy drinks that count as "dietary supplements, which are legally exempt from regulation," Miller added. Although these extracts are mostly present in low doses, their effects are unclear and could be potentially harmful, she said.

So, while energy drinks might keep you awake, there's no guarantee that excessive use will keep you healthy.

Originally published on Live Science.

What does coffee have to do with cannabis? According to a new study, your morning joe causes a drop in the levels of certain substances that are linked to the body's system for responding to marijuana.

The levels of these substances — metabolites found in what's known as the endocannabinoid system — decrease in people who drink between four and eight cups of coffee a day, according to the study, published today (March 15) in the Journal of Internal Medicine. Endocannabinoids are molecules that bind to cannabinoid receptors, which are found all over the nervous system, as well as in immune and endocrine tissue. The body makes its own endocannabinoids, but it also responds to foreign cannabinoids, like the ones found in the leaves of plants of the Cannabis genus.

Coffee suppresses the endocannabinoid chemicals that smoking marijuana boosts, said Marilyn Cornelis, an assistant professor of preventative medicine at Northwestern University's Feinberg School of Medicine, who led the new research. [25 Odd Facts About Marijuana]

That would suggest that coffee might generate the opposite effects as cannabis on the endocannabinoid system, Cornelis told Live Science.

Your blood on coffee

The research didn't look at the sensations or behaviors that coffee produces compared to cannabis, only at the rise and fall of chemicals in the blood after coffee consumption. Endocannabinoids were just one set of the chemicals — or metabolites — that changed, the researchers found. All told, coffee altered 115 different metabolites in the blood. Thirty-four of those metabolites don't even have names or known roles in the body. The other 82 known metabolites play roles in 33 different biological processes.

Cornelis and her team focused on five of these specific biological processes where numerous metabolites seemed to cluster. Two of the processes were expected: One was xanthine metabolism — a set of processes that includes caffeine metabolism, which made sense, because the body naturally has to metabolize the caffeine in coffee once it is consumed. The other pathway, benzoate metabolism, in involved in breaking down other compounds in coffee called polyphenols. The compounds are broken down by microbes that live in the gut, Cornelis said. The gut microbiome is under increased scrutiny for its role in health, so the finding is intriguing, she said.

But the real surprises were three other metabolic processes never before linked with coffee. Endocannabinoids were clustered in one of those processes.

"What we're seeing here is that the systems that are impacted by coffee and cannabis overlap," Cornelis said. That could mean that drinking coffee with marijuana in your system could create interacting effects, she said, though the nature of those interactions isn't yet clear. Typically, she said, the same endocannabinoids that declined with coffee also decrease when the body is under stress. It's possible that the amount of coffee that participants were drinking (four to eight cups a day) caused stress, which led to a drop of endocannabinoid levels as some kind of protective measure.

Cornelis and her team also found that coffee consumption increased the concentration of steroid metabolites in the blood, possibly because coffee contains plant steroids called phytosterols. In particular, the metabolites that increased are linked to steroid excretion, Cornelis said, so it's possible that coffee could boost steroid breakdown in the body. (Greater steroid breakdown would lead to greater steroid excretion.)  

What this finding means for human health remains a mystery. Some steroid processes have links to certain cancers, Cornelis said, and the link between coffee itself and cancer is fuzzy, so the steroid finding could provide a new place to look to understand whether coffee consumption affects the likelihood of a person developing cancer.

The final grouping of metabolites changed by coffee consumption consisted of fatty acid acylcholines, which may be linked with the endocannabinoid pathway, Cornelis said. But the changes there are the most mysterious of all.

"That's a novel set of metabolites that we don't really know how to explain," she said.

Coffee and health

That the study raised more questions than answers is no surprise: Cornelis went into the research hunting for new links between coffee and health. Plenty of research has associated coffee drinking with health effects, she said — so much so that Coffee Is Good For You/Coffee Is Bad For You headlines are almost a cliche. [10 Things You Need to Know About Coffee]

But those are just statistical associations, Cornelis said. "The goal of my research is to understand the causal reasons that link coffee to those outcomes."

The current study is based on a years-old clinical trial conducted in Finland, where 47 coffee drinkers were asked to abstain from the brew for one month, then drink four cups a day for a month, then escalate to eight cups a day for the final month of the study. All participants drank the same medium-roast arabica blend, which is also the most popular type of coffee in the United States, Cornelis said. Cornelis and her team used the blood of these participants to test 733 metabolites.

The same people were also tested for changes in their levels of lipids and proteins, which is what Cornelis is studying next. She also hopes to use other data from large, population-based studies that included data on coffee consumption to see if the same metabolites change in broader populations.

"It would be interesting to see if there were some genetic differences in the response to coffee as well," she said.

Originally published on Live Science.

Hot tea may do more than warm your insides: Drinking at least one cup of caffeinated tea a day may lower a person's risk for glaucoma, a new study suggests.

Researchers found that daily hot-tea drinkers were 74 percent less likely to be diagnosed with glaucoma, compared with those who drank no tea, according to the study, which was published today (Dec. 14)in the British Journal of Ophthalmology.

Glaucoma is a leading cause of vision loss and occurs when pressure builds up inside the eye. This pressure may damage the optic nerve and cause vision loss or blindness. Cases of this serious eye condition are on the rise worldwide, according to the study. [9 Healthy Habits You Can Do in 1 Minute (Or Less)]

The new findings show that lifestyle changes could help prevent vision loss from glaucoma, said lead study author Dr. Anne Coleman, a professor of ophthalmology at the David Geffen School of Medicine at the University of California, Los Angeles.

In the study, the researchers reviewed data from the 2005-2006 National Health and Nutrition Examination Survey (NHANES), a yearly survey evaluating the health and diet of people in the U.S. The researchers used that year because it also included eye test results for glaucoma.

Of the 1,600 men and women who had eye tests in the survey, about 5 percent had glaucoma, according to the study.

To determine whether beverage choice had any ties to glaucoma risk, the researchers looked at the NHANES data, which included information on how frequently the survey respondents said they had consumed coffee, tea or soft drinks during the past 12 months.

The researchers found that coffee lovers outnumbered fans of hot tea, but only a daily cup of caffeinated hot tea was tied to a lower risk of glaucoma. This finding held true even after factoring in whether someone smoked or had diabetes, both of which can affect glaucoma risk, the study said.

Interestingly, though the study showed a link between caffeinated hot tea and glaucoma risk, the results did not show a similar association between decaffeinated hot tea and the eye condition.

One possible explanation for this finding is that teas containing caffeine have more antioxidants than decaffeinated teas do, Coleman said. [4 Awesome Perks of Drinking Tea]

In addition, there was no evidence that other beverages had protective effects: The analysis did not find that drinking hot coffee (either caffeinated or decaf varieties) or caffeinated iced tea or soft drinks every day was associated with a lower risk of developing glaucoma.

The researchers noted that the study did not prove cause and effect, but rather found merely an association between drinking hot tea and glaucoma risk.

But why might people's beverage choice affect eye health?

It could be that tea contains phytochemicals and flavonoids, and these plant compounds have anti-inflammatory and antioxidant properties that may protect the eye and the nerves surrounding it, Coleman told Live Science. Caffeinated tea drinkers may also have other healthy behaviors, such as getting more exercise or drinking less alcohol, that the researchers had not considered, she said.  

As for coffee, it contains more caffeine and fewer flavonoids than tea, the study authors said. And the lack of protective effects observed with iced tea may be due to the small sample size of people who regularly drank the beverage, Coleman said. 

One of the study's limitations is that no information was collected about the type of tea consumed, the brewing method, how long the tea steeped or the cup size used, the researchers said.

Originally published on Live Science.

A company that claims to make one of the strongest coffees in the world is recalling some of its products because they could pose a risk of serious illness.

On Tuesday (Sept. 19), Death Wish Coffee Co., which brands itself as the "world's strongest coffee," said it was recalling all of its 11-ounce Nitro Cold Brew cans because the products could pose a risk of botulism, a serious and sometimes deadly illness caused by the botulin toxin. The company said it had determined that its current manufacturing process for the cans could lead to the growth of the bacteria that produce the botulin toxin, which can occur in low-oxygen and low-acid foods.

"Our customers' safety is of paramount importance and Death Wish Coffee is taking this significant, proactive step to ensure that the highest quality, safest and, of course, strongest coffee products we produce are of industry-exceeding standards," Mike Brown, the founder and owner of Death Wish Coffee, said in a statement. "We apologize for the inconvenience this may cause our customers and our retail partners, but we believe this is the right precautionary measure to take."

So far, no illnesses have been reported in connection with the recalled products.

Death Wish coffee contains more than 700 milligrams of caffeine per 12 fluid ounces, according to the company. That's nearly twice the recommended daily limit of caffeine, which is 400 mg. Its Cold Brew product contains less caffeine, about 380 mg per can. For comparison, a 12-ounce cup of dark roast coffee at Starbucks has about 200 mg of caffeine. [10 Interesting Facts About Caffeine]

The company, which is based in Round Lake, New York, said it was halting production of its Cold Brew cans until an extra step is added to their manufacturing process to address the botulism risk.

Death Wish Coffee has pulled its cans from store shelves and removed them from its website. In addition, customers who purchased the cans through the Death Wish website will receive a full refund within 60 days, the statement said.

The botulin toxin attacks the body's nerves and can cause difficulty breathing, muscle paralysis and death, the Centers for Disease Control and Prevention says. Symptoms of botulism include blurred vision, drooping eyelids, slurred speech, difficulty swallowing and muscle weakness. People experiencing these symptoms should seek immediate medical attention, Death Wish Coffee said.

Original article on Live Science.

Eighty percent of Americans get a daily jolt from caffeine, and now, as marijuana legalization has spread across the nation, some users and businesses have begun touting a combination of the two drugs.

"After years of smoking, I've found that caffeine and weed are a perfect mix. If I get nicely stoned then drink a strong cup of coffee, the effects mix so perfectly," wrote one Reddit user.

A company called Cannabiniers recently tapped into the trend with the launch of Brewbudz, which are cannabis-infused coffee, tea and cocoa pods that pop into any Keurig coffee brewer. [25 Odd Facts About Marijuana]

But what happens when you combine the drugs, and are there possible dangers?

It's important to keep in mind that the caffeine in a regular cup of coffee or tea is a pretty powerful psychoactive drug, meaning it’s capable of affecting the mind, emotions and behavior, Dr. Sergi Ferre, a senior investigator at the National Institute on Drug Abuse (NIDA), told Live Science.

Caffeine exerts its effects by blocking receptors in the brain for a neurotransmitter called adenosine, Ferre told Live Science. Adenosine is an inhibitory neurotransmitter, meaning that it blocks other neurotransmitters that excite the neurons; its activity thus leads to feelings of fatigue. So, by blocking adenosine, caffeine changes peoples' moods and leaves them feeling more alert and awake.

Caffeine is also known to boost another neurotransmitter: dopamine, Ferre said. This neurotransmitter is often called the "feel-good" chemical, because it's responsible for feelings of pleasure and reward. It just so happens that tetrahydrocannabinol (THC), the active ingredient in marijuana, is also known to stimulate dopamine neurons throughout the brain, he said.

Indeed, one reason why people may like the combination of marijuana and caffeine so much is that caffeine can magnify the effects of dopamine released by marijuana.

"Caffeine increases tremendously the effects of a psychostimulant, including THC and cocaine," Ferre said. "So, any substance that releases dopamine, including THC, its effects are increased by caffeine."

Magnified marijuana

That enhancement may be why more people are combining the drugs, but Ferre cautioned that doing so is a bad idea. Using caffeine with any psychostimulant drug, and enhancing the drug's high, can make the drug much more addictive than it would be if it was used alone, he said. [7 Ways Marijuana May Affect the Brain]

Ferre and colleagues published a 2014 study in The Journal of Neuroscience that tested the effects of combining THC with a compound called MSX-3 that mimics some of the effects of caffeine. In experiments on squirrel monkeys that were addicted to THC, the researchers measured whether a range of doses of the caffeine-like compound influenced the monkey's likelihood to give themselves more hits of THC.

The researchers concluded that the caffeine-like compound enhanced the effects of THC at any dose.

 Caffeine "is not good, at any dose, to associate with THC," Ferre said.

Another cause for concern is that adding caffeine may worsen the memory impairment commonly associated with using marijuana, he said.

A 2012 study in rats, also by Ferre and colleagues, showed that combining caffeine with marijuana worsened the memory problems induced. The effect is likely to be particularly acute in teens, because their brains are still developing, Ferre said.

"The worst is with kids," Ferre said. "Caffeine can be a really powerful drug that can have strong effects on a developing brain."

Questions remain

Although Ferre's research presents significant warning flags about combining caffeine with marijuana, not all experts agree. [Marijuana Could Treat These 5 Conditions]

In general, there is not much research on marijuana and its effects, said Gary Wenk, a professor of psychology, neurology and molecular virology at the Ohio State University. Marijuana is classified as a Schedule 1 drug under the Controlled Substances Act, meaning the drug is considered to have a high potential for abuse and no medical use.

"There has been very little research, because there is a lack of funding," Wenk told Live Science. "The National Institute on Drug Abuse does some research, but it's all related to treatment or determining ways it's harmful. But otherwise, it's hard to get funded, because it's a Schedule 1 drug."

Despite the lack of research on marijuana's effects, an increasing number of Americans are using the drug. Currently, around one-fifth of Americans now live in states where marijuana is legal for adults to use recreationally, according to the Brookings Institution, and some 200 million live in places where it's legal to use the drug for medical reasons.

Aside from being cautious, in recognition of what research there is on the effects of combining caffeine and marijuana, Wenk said that users are, to some extent, on their own.

"When people ask, 'How will it affect me?' you have to ask, 'What are your genes? What are your vulnerabilities?'" Wenk said. "Combining the drugs will have a different effect on different people, so it can be hard to predict."

Originally published on Live Science.

Drinking coffee may do more than help wake you up — it may also help you live longer, two large new studies suggest.

Both studies — one from the United States and the other from Europe — found that people who drank caffeinated or decaffeinated coffee every day were less likely to die over a period of about 16 years, compared with people who didn't drink coffee.

Moreover, the more cups of joe people consumed each day, the less likely they were to die from any cause during the studies than people who were not coffee drinkers, according to the findings, which were both published online yesterday (July 10) in the journal Annals of Internal Medicine. [10 Interesting Facts About Caffeine]

These studies are in line with earlier findings that also showed a connection between higher rates of coffee consumption and a reduced risk of death, the researchers said. However, the previous studies had been done in largely white populations, and there was limited data on whether the effect would be seen in nonwhite populations.

In one of the new studies, the researchers analyzed data collected from more than 215,000 adults in the U.S., ages 45 to 75. Participants included African-Americans, Japanese Americans, Latinos, Native Hawaiians and Caucasians, who lived in Los Angeles or Hawaii and were all enrolled in the Multiethnic Cohort, an ongoing study examining lifestyle risk factors that may cause cancer in minority populations.

People's lifestyle habits, disease risks and genetic susceptibilities to cancer vary widely across different races and ethnicities, so the new finding that again linked coffee drinking with a lower risk of dying offers stronger evidence that coffee drinking is protective and is associated with lower mortality, said Veronica W. Setiawan, the lead author of that study and an associate professor of preventive medicine at the University of Southern California's Keck School of Medicine in Los Angeles.

At the beginning of the study, each participant completed a lifestyle and dietary questionnaire asking them to describe how frequently they drank regular or decaffeinated coffee in the past year. The researchers found that during an average follow-up period of about 16 years, there were about 58,000 deaths among the participants.

The analysis also showed that participants who consumed an average of one cup of regular or decaffeinated coffee a day had about a 12 percent lower risk of death than participants who drank no coffee.

Participants who downed two to three cups of coffee a day, on average, were about 18 percent less likely to die than people who drank no java, according to the findings. The results held true in four out of five ethnic groups studied — all except Native Hawaiians — even after researchers took into account factors that could influence people's coffee habits or their risk of death, such as smoking, alcohol use, physical activity and pre-existing illness. [Extending Life: 7 Ways to Live Past 100]

The mortality rates found in this study are quite comparable to the data from white populations, Setiawan told Live Science. It's unclear why coffee may reduce a person's risk of dying, but the popular beverage has many biologically active compounds that may play a role, because they have antioxidant and anti-inflammatory properties, she said.

European coffee drinkers

Although the American study did not ask the participants any questions about coffee- preparation methods, the other study, which was done in Europe, took this information into consideration. The researchers said they suspected that different preparation methods and drinking customs in different countries could affect people's risk of dying.

For this study, researchers examined data collected from 520,000 men and women, most of whom were ages 35 and older, in 10 European countries (Denmark, France, Germany, Greece, Italy, the Netherlands, Norway, Spain, Sweden and the United Kingdom). All of the participants were enrolled in the European Prospective Investigation into Cancer and Nutrition, an ongoing trial of the relationship between diet and cancer. 

Each of the European participants were asked via questionnaire or in an interview about their typical coffee consumption per month, week or day as well as whether they drank caffeinated or decaffeinated versions of the beverage. The study found that participants in Denmark drank the most coffee, while Italians drank the least. [Coffee's Perks: Studies Find 5 Health Benefits]

The researchers also had access to other information about the participants' diet and lifestyle habits, as well as the results of lab tests to evaluate their health status.

During an average follow-up period of about 16 years, more than 41,000 participants died.

The findings revealed that participants who consumed higher amounts of coffee, about three cups a day, had a lower risk of death from any cause than participants who drank no coffee.

Men who drank three or more cups of coffee per day had an 18 percent lower risk of death, compared with men who drank no coffee, said lead author Marc Gunter, the head of the section of nutrition and metabolism at the International Agency for Research on Cancer in Lyon, France. 

Women who drank three or more cups of coffee per day had an 8 percent lower risk of death during the study, compared with women who consumed no coffee, Gunter said. Although the size of the effect is not a large one, it's overall health impact on the population could be considerable because coffee is such a commonly consumed beverage, he said.

When the researchers looked at specific causes of death they found that participants who consumed higher amounts of coffee were less likely to die from digestive diseases and circulatory diseases, such as heart attack and stroke.

Similar reductions in people's risk of dying were observed across all 10 European countries, which had different coffee-drinking habits and customs, Gunter told Live Science.

All in all, the findings suggest that moderate coffee drinking, meaning up to three cups per day, is not detrimental to your health, Gunter said. "Incorporating coffee into your diet could have health benefits," he said.

Originally published on Live Science.

A teen in South Carolina has died after drinking three caffeinated beverages over a 2-hour period.

The 16-year-old boy drank a large diet Mountain Dew, a McDonald's cafe latte and an unnamed energy drink in that time, USA Today reported today (May 16).

The Richland county coroner, Gary Watts, said the teen's death was caused by a "caffeine-induced cardiac event causing a probable arrhythmia," according to USA Today. In other words, the caffeine caused a heart problem that could have led to an irregular heartbeat. Watts also said that the teen was healthy and didn't have any medical problems that the caffeine could have exacerbated. [10 Interesting Facts About Caffeine]

About 400 milligrams of caffeine a day, or four cups of coffee, is considered safe for healthy adults, according to the Mayo Clinic.

So how does caffeine cause such heart problems? And how could it lead to death at a young age?

"Caffeine is a stimulant," said Dr. Lewis Nelson, the chairman of emergency medicine at Rutgers New Jersey Medical School in Newark, who was not involved in the teen's case.

In general, stimulants "raise [a person's] heart rate and can cause some people to have" heart problems, Nelson told Live Science. In particular, stimulants can disrupt the heart's regular rhythm, he said.

Caffeine can also cause a person to have "difficult-to-treat seizures," and these can make the effects on the heart worse, Nelson added.

Dr. Amy Durso, the deputy chief medical examiner for Richland County, South Carolina, where the teen lived, said it's the amount of caffeine and the time frame over which it's ingested that can put a person at risk, according to The State, a South Carolina newspaper.

"A cup of a coffee, a can of soda isn't going to cause this thing," Durso told The State.

Indeed, the director of the South Carolina Coroner's Association, Dennis Fowler, told The State that he's never seen this happen before.

However, caffeine's effects on the heart have been documented.

In a 2015 study, published in the journal JAMA, researchers measured the blood pressure and hormone levels of healthy adults before and after they drank 16 ounces of an energy drink. They found that both of these increased after people consumed the drink.

These changes may put people at risk for heart problems, the researchers wrote in the study.

In addition, a case report from August 2016 described a 28-year-old man's heart problems that landed him in the emergency room after drinking two energy drinks a day, plus alcohol, for months. The doctors who treated the man reported that his heart rate was fast and that he had an irregular heartbeat.

Originally published on Live Science.

Consuming energy drinks may be particularly risky for people with a certain genetic heart condition, a new study from Australia suggests.

The study looked at 24 people who had inherited long QT syndrome, a condition that can cause dangerous irregular heartbeats. About one person in every 2,000 has this condition, the researchers said.

Participants in the study received either two sugar-free energy drinks containing a total of 160 milligrams of caffeine plus 2,000 mg of the chemical taurine, or a control drink, which consisted of juice that didn't contain any caffeine or taurine. A chemical that's often added to energy drinks, taurine has been purported to enhance mental and athletic performance. Participants in the study weren't told whether they'd received the energy drink or the control drink.

The results showed that participants' blood pressure increased significantly when they consumed the energy drink, compared to when they consumed the control drink, the study said.

What's more, after consuming the energy drink, three participants experienced a dangerous increase in a part of their heartbeat's electrical cycle known as the QT interval. This interval corresponds to the time it takes for the heart to contract and refill with blood, according to the Mayo Clinic. Although this prolonged QT interval doesn't always cause problems, it can trigger life-threatening irregular heartbeats in people with long QT syndrome. [10 Interesting Facts About Caffeine]

"The potential cardiovascular risk of energy drinks continues to emerge as an important public health issue," study co-author Dr. Christopher Semsarian, a cardiologist and professor at the University of Sydney in Australia, said in a statement. The researchers said that people with long QT syndrome should be cautious about consuming energy drinks.

Many previous studies have found links between energy-drink consumption and heart problems. For example, one study published in 2015 found that consuming just one energy drink can increase blood pressure in healthy people. And there have been several reports of young people who have suffered heart attacks or abnormal heart rhythms after consuming energy drinks.

Dr. Peter Schwartz and Dr. Federica Dagradi, of the Center for Cardiac Arrhythmias of Genetic Origin in Milan, Italy, who wrote an editorial accompanying the new study, said the findings deserve careful consideration. They noted that patients with long QT syndrome often don't discover they have the condition until after their teen years.

This "implies that a significant number of youngsters with [long QT syndrome] will help themselves to energy drinks without knowing their real condition and thus endangering themselves," Schwartz and Dagradi wrote.

Still, the researchers did not find an increase in the QT interval among all participants, which suggests that some people with the condition may be at higher risk than others for this effect.

The study and the editorial were published March 15 in the International Journal of Cardiology.

Original article on Live Science.

Caffeine could counteract the inflammation that comes with aging, a new study finds.

The difference could come down to just a few cups of coffee a day, study co-author and Stanford University professor of microbiology and immunology Mark Davis told Live Science. The study's findings may explain why coffee drinkers tend to live longer than those who do not drink coffee, the researchers suggested in a statement from Stanford University.

The study had a few parts: First, researchers analyzed data from more than 100 people who are taking part in an ongoing study, called the Stanford-Ellison cohort, which aims to investigate how the system changes during aging. The researchers reviewed the participants' blood samples, survey data and medical and family histories. [10 Interesting Facts About Caffeine]

The results showed that the older participants had higher levels of an inflammatory protein, called IL-1-beta, compared with the younger participants. What's more, among the older participants, those with higher levels of IL-1-beta had a greater risk of stiff arteries, high blood pressure and mortality during the study period, compared with those who had lower levels of this inflammatory protein.

To identify whether there was any causal link between IL-1-beta and conditions like high blood pressure, researchers then conducted a study on mice. The scientists found that injecting the mice with substances that increased the production of IL-1-beta triggered large amounts of inflammation and hypertension, supporting the idea of a cause-effect relationship, said Davis.

Next, researchers investigated why some older adults showed lower activation of the genes that encode IL-1-beta, and found an interesting correlation: The older participants who reported that they consumed more caffeinated beverages generally showed a lower activation of these inflammation-causing genes.

When researchers looked again at the blood samples of the older participants, they found that those whose blood had higher levels of caffeine and its breakdown products showed lower activation of these genes than participants whose blood had lower levels of caffeine and its breakdown products.

Researchers then turned to the laboratory again to confirm a cause-effect relationship. This time, they added caffeine into human immune cells growing in lab dishes, along with compounds that would trigger inflammation. Results showed that caffeine actually prevented these compounds from causing inflammation in cells. [10 Things You Need to Know About Coffee]

This finding may "explain why caffeine consumption correlates with lower blood pressure," Davis told Live Science.

The researchers noted in their study that lowering chronic inflammation in older people may prevent a number of age-associated diseases, including high blood pressure, stiff arteries and other cardiovascular problems, although more research is needed to confirm this.

For now, drinking coffee may be one way to decrease the inflammatory processes that naturally come with age, the researchers wrote in their paper.

But the researchers said they hope their work will spur other scientists to develop more sophisticated drugs that could target these culprits of inflammation.

Originally published on Live Science.

What you should know

People may not think of caffeine as the most popular mood-altering drug in the world, even those who use it daily, by drinking coffee, tea, sodas or energy drinks as part of their routine. 

Yet many of us depend on regular doses of 1,3,7 trimethylxanthine, the chemical name for a bitter white powder known as caffeine, to help wake us up, keep us alert and get us through the daily grind.

Whether it's brewed from a K-Cup, sipped in sweet tea, savored in chocolate or downed in cola, caffeine is a mild stimulant to the central nervous system that has become a regular fixture in everyday life. 

In moderate amounts, caffeine has been shown to have positive effects on people's bodies and minds. There's some evidence that caffeine may help improve memory, enhance workouts and boost concentration.

The Food and Drug Administration considers 400 milligrams a safe amount of caffeine for healthy adults to consume daily. However, pregnant women should limit their caffeine intake to 200 mg a day, according to the American College of Obstetricians and Gynecologists. (One cup of coffee usually has about 100 to 200 mg, a cup of tea usually has no more than 70 mg and most sodas have less than 50 mg, according to the Mayo Clinic.)

The Mayo Clinic suggests that teens limit their caffeine intake to 100 mg a day and recommends that younger children avoid caffeine.  [5 Experts Answer: Is Caffeine Bad for Kids?]

Some people are highly sensitive to caffeine's effects. Caffeine can lead to headaches or an upset stomach, and may cause people to have trouble sleeping, feel jittery or get heart palpitations, when their intake is high (about four cups of coffee a day), studies (and anecdotal observations) suggest.

Here are 10 interesting facts about caffeine to mull over while nursing that first cup of joe. 

Caffeine stays in the body for hours

Caffeine is absorbed into the blood and tissues within about 45 minutes of being consumed. But it takes much longer than that for the body to break it down and clear it from a person's system.

The half-life of caffeine, or the time it takes to eliminate one-half of the caffeine people have in their bodies, is about 4 hours, said James Lane, an emeritus professor of psychiatry at Duke University School of Medicine in Durham, North Carolina. But that doesn't mean that all of the caffeine is gone after 8 hours, in fact, it may take 12 hours to completely eliminate the caffeine in a morning cup of coffee, said Lane, who has studied the health effects of the drug.

Caffeine's half-life may be shortened to about 3 hours in people who smoke, Lane said. In contrast, women who take birth control pills may keep caffeine in their systems for up to 4 hours longer than women who are not on the pill, according to one study. [7 Surprising Facts About the Pill]

Pregnancy can extend caffeine's half-life even more, lengthening it to 10.5 hours during the final four weeks of pregnancy, according to one study.

Because it can take up to 12 hours to clear caffeine from the body, the drug often wears off when a person is almost ready to go to bed. This makes it easier for people to develop a dependency on caffeine because it makes people want to continue to drink it the next day, Lane said.

The reason people who regularly drink caffeine wake up feeling groggy, confused or with a headache is that they are experiencing withdrawal symptoms from yesterday's coffee, Lane said. These withdrawal symptoms are relieved when they get their morning fix of caffeine.

Death from too much caffeine is rare, but possible

In rare instances, when caffeine is consumed at high enough doses (typically in excess of 5 grams in adults — the amount in about 30 to 50 cups of coffee), it can kill.

Deaths have been reported from overdosing on powdered caffeine and caffeine pills, such as weight-loss aids. [7 Foods You Can Overdose On]

In 2014, two young men — an 18-year-old in Ohio and a 24-year-old in Georgia — overdosed on pure powdered caffeine, according to the FDA. Their deaths illustrate the dangers and potency of this concentrated product. One teaspoon of pure powdered caffeine contains about the same amount of caffeine as 28 cups of regular coffee, according to the FDA.

The FDA warns that young people, in particular, might use powdered caffeine — which is sold legally online — to boost their energy level, study longer, improve their athletic performance or lose weight.

But the powder is 100 percent caffeine, making it a powerful stimulant that, in even very small amounts, may trigger an accidental and potentially fatal overdose. Further complicating matters is that safe quantities of powdered caffeine can be nearly impossible to measure accurately with kitchen teaspoons, the FDA said.

Signs of caffeine toxicity might include a racing heart, sweating, seizures, vomiting, muscle tremors and, eventually, respiratory collapse, Lane said.

It was involved in soda snafu

Although it contains less caffeine than a small cup of coffee, a 12-ounce can of Sunkist Orange soda has 41 milligrams of caffeine in it, according to the Center for Science in the Public Interest. Other brands of orange soda are usually noncaffeinated, but Sunkist Orange has more caffeine in it than a similar amount of Coca-Cola or Pepsi.

In September 2010, the makers of Sunkist Orange recalled nearly 4,000 cases of the 12-ounce bottled version of the beverage after receiving customer complaints that the soft drink had a medicinal taste to it and was causing stomachaches, vomiting and even hospitalization, according to the book "Caffeinated: How Our Daily Habit Helps, Hurts, and Hooks Us" (Hudson Street Press, 2014) by Murray Carpenter.

After looking into it, the manufacturer determined that human error was to blame for the incident: The reason for the off-taste and sickness was that a batch of the orange soda had been accidentally blended with six times as much caffeine as it should have, they said, according to the book.

Each bottle contained about 238 milligrams of caffeine, an amount equivalent to what's found in three Red Bulls, about seven cans of regular cola or 16 ounces of strong coffee, according to the book. Because orange soda is popular with kids, this high dose of caffeine possibly made a few children uncomfortable because they may not have realized why they felt that way.

Consumers were never informed of the supercaffeinated snafu because the FDA considered it a Class III recall, meaning "a situation in which exposure to the product is not likely to cause adverse health consequences," according to the book.

Caffeine withdrawal is a real condition

In the latest version of the psychology handbook "Diagnostic and Statistical Manual of Mental Disorders" (DSM-5), caffeine withdrawal is listed as a mental health condition. The text describes the effects seen in some people who abruptly stop or dramatically cut back on their daily use of caffeine.

For example, withdrawal side effects, which may start 12 to 24 hours after stopping or drastically curbing caffeine, include a throbbing headache, fatigue, irritability, depressed mood and difficulty concentrating, according to the book. In people diagnosed with the condition, these symptoms are typically severe enough to interfere with a person's ability to function properly at work or in social situations, the mental health manual suggests.

People who regularly consume caffeine wake up every morning in caffeine withdrawal, Lane said. But they might not think of it that way, he added. Instead, people typically consider morning grumpiness, fuzzy thinking and sleepiness as signs of not yet having their coffee.

"The truth is, these are signs of caffeine withdrawal," Lane told Live Science.

Cutting back gradually on caffeine over the course of a week may help to avoid a withdrawal headache.

People aren't truly "addicted" to caffeine.

People who consume caffeine every day are most likely dependent on the drug, and it does produce symptoms of dependence, Lane said. But addiction is not the best way to describe it, he said.

Caffeine use is socially acceptable, and because people who consume it in large amounts aren't thought of as acting like addicts, society doesn't put its overuse in the same category as that of other drugs, Lane said. [5 'Hidden' Sources of Caffeine]

Caffeine is not highly addictive, said Dr. Peter Martin, a professor of psychiatry and pharmacology at Vanderbilt University School of Medicine, and the director of the Institute for Coffee Studies at Vanderbilt University in Nashville.

Generally, people's need for caffeine is a different order of magnitude compared with an addiction to opioid drugs or cocaine, Martin said. "Caffeine has minor-league side effects compared with real addictive drugs," he said. 

A person might say, "I'm addicted to coffee," to describe their habitual need for caffeine, but Martin, who is a specialist in addiction psychiatry, said he would ask that individual, "When was the last time you robbed a bank to get money to buy coffee?"

Caffeine resembles a brain chemical

Caffeine has a similar molecular structure to adenosine, a neurotransmitter (a substance that transmits nerve impulses in the brain). Because of its chemical resemblance to adenosine, caffeine can bind to adenosine receptors in brain cells.

Caffeine's stimulant effects come mainly from the way it acts on the brain's adenosine receptors. Normally, the binding of adenosine to its receptors produces drowsiness and depresses the central nervous system, which slows down nerve cell activity and promotes relaxation, Martin said.

But when caffeine molecules take the place of adenosine and bind to these same receptors, it blocks the sleep-inducing actions of adenosine and speeds up nerve cell activity. This causes a person to feel temporarily more awake and energetic, Martin told Live Science.

Caffeine can be found in unusual places

These days, consumers might notice caffeine in some unexpected places. People can purchase caffeine-infused bottled water, jelly beans, breath mints, peanut butter and chewing gum.

There are even caffeinated bath soaps that supposedly help wake people up in the morning. Although caffeine can be absorbed through the skin, it's doubtful this soap will improve alertness during the day, Lane said.

Caffeine has also been added to shampoos to purportedly thicken hair and stop hair loss, but there's no good evidence that these pricey products can truly deliver results.

The beauty industry has jumped aboard the caffeine bandwagon, by adding it to everything from eye cream and lotions to body scrubs and shaving cream. Whether products containing the ingredient work better than their noncaffeinated counterparts is questionable.

In addition, drug makers have added caffeine to headache medications, such as Excedrin and Anacin, because it may enhance the effectiveness of pain medications and bring faster relief, according to headache specialists. It's even in the menstrual pain reliever Midol Complete.

College students who pull all-nighters may be familiar with caffeine pills, also called "alertness aids," such as NoDoz and Vivarin, each of which contain 200 milligrams per pill. 

In addition, caffeine is in some weight-loss products and dietary supplements. It may be listed on the label as guarana, kola nut, yerba mate, green tea extract or green coffee bean extract, according to the National Institutes of Health.

Coffee beans come from a red fruit

The fragrant brown beans that people might toss into a grinder every morning actually come from a bright-red fruit.

Coffee comes from shrubs, known as coffee cherries, that produce a red berry when ripe, Lane told Live Science. The actual coffee beans, which are green, are found inside the coffee cherries. 

Coffee often has to be picked by hand because the red fruit doesn't all mature at the same time, Lane noted.

Before the beans were used to make coffee, the pulp from the red fruit was first fermented and used to make a wine, he said. Some time around 1000 A.D., people in Arabia began to roast coffee beans to make a beverage from them.

But according to the National Coffee Association, an industry trade group, an Ethiopian goat herder named Kaldi first discovered the stimulant powers of coffee around 800 A.D., when he found his goats dancing and frolicking in the fields after grazing on the red berries from a coffee shrub. After seeing its effects on his goats, Kaldi also tried the coffee cherries. He had a similar reaction to them. [Coffee's Perks: Studies Find 5 Health Benefits]

Then, a monk who supposedly observed Kaldi and his goat's odd behavior plucked some berries and took them back to his monastery for his brothers to try that night. After consuming the fruit, they became more alert and attentive during long hours of evening prayer. According to legend, the monks came up with the idea of drying the fruits and boiling them into a beverage.

It's as if coffee cherries were the answer to the monks' prayers — or at least their ability to stay awake during them. 

Caffeine can exaggerate the effects of stress

Lane's research has found that caffeine can amplify stress in people who consume it every day. In a small study of habitual coffee drinkers, he found that caffeine amplifies the stress response in the body, resulting in increases in blood pressure and heart rate, as well as increases in the production of stress hormones.

Caffeine directly affects not only the way a person's body responds to stress but also the mind by magnifying an individual's perception of stress.

An exaggerated stress response can make a difference to people with conditions such as high blood pressure and type 2 diabetes, Lane said.

In fact, he encourages people with these conditions, as well as people with prediabetes or borderline hypertension who are not yet on medication, to try eliminating coffee and other caffeinated beverages to see if it lowers their blood pressure or blood sugar levels.

Lane said lower blood pressure readings may occur within a few days of quitting caffeine, but it may take several months for people to see reductions in blood glucose.  

Caffeine in plants acts as a natural pesticide and herbicide

Caffeine is found in the leaves, fruits and seeds of some caffeine-producing plants, including coffee and tea shrubs, kola and cacao trees, guarana and yerba mate from South America.

Caffeine in plants function as a natural pesticide to help ward off insects that may attack the plants, and it may be useful in pest control, suggested a study from researchers at Harvard Medical School that was published in 1984 in the journal Science. At high doses, caffeine can even be toxic to insects.

Caffeine is also a natural herbicide that gets released into the soil so that weeds can't grow near coffee and tea shrubs, Lane said. Weeds might compete with the shrubs for nutrients, he noted.

Lane also said that on coffee farms, caffeine can build up so much in the soil that the coffee plants themselves might suffer.

Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

If one cup of coffee keeps you perked up all day, you may be able to thank your genes for that long-lasting caffeine kick, a new study finds.  

Scientists in Scotland have identified a gene that may play a role in how the body breaks down caffeine, according to the study — and variations in this gene may influence how much coffee a person drinks.

In people with a certain variation of a gene called PDSS2, caffeine is broken down in the body more slowly, according to the study, which was published today (Aug. 25) in the journal Scientific Reports. Slower breakdown means that the caffeine stays in the body longer, so a person doesn't need to drink as much coffee to get the same effects, the researchers said. [10 Interesting Facts About Caffeine]

In the study, the researchers examined the DNA of more than 1,000 people in northern and southern Italy and more than 1,700 people in the Netherlands. Everyone in the study also filled out a questionnaire that included questions about how much coffee they drank each day. 

Among the Italians in the study, those who had a certain variation in their PDSS2 gene tended to drink less coffee, by about one cup a day, on average, than those who did not have the variation, the researchers found.

The reason might be that people with this gene variation break down caffeine more slowly, so the chemical stays longer in their bodies, and they tend to drink less, the researchers said.

Similarly, among the Dutch people in the study, those with that same gene variation also drank less coffee each day, on average, though the difference was not as large as the difference observed in the Italians, according to the study.

This discrepancy may be due to the fact that coffee-drinking styles vary in the two countries, the researchers added. In Italy, people typically drink small cups of espresso or mocha, whereas in the Netherlands, it is more common for people to drink filtered coffee. These differences in preparation result in different amounts of caffeine per cup. Indeed, the intake of caffeine per cup among the Dutch is almost three times higher than that of Italians, according to the study.

The PDSS2 gene isn't the only gene that's been linked to caffeine consumption, however. Previous research has shown that other genes that code for enzymes that break down caffeine are also linked to how much coffee people drink, according to the study.

It's possible that PDSS2 blocks the expression of these enzymes, the researchers wrote. By blocking the enzymes, the body doesn't break down caffeine as efficiently, they wrote.

"The results of our study add to existing research suggesting that our drive to drink coffee may be embedded in our genes," said Nicola Pirastu, a research fellow in statistical and quantitative traits genetics at the University of Edinburgh and the lead author of the study.

More research is still needed to understand the link between the genetic variation and coffee consumption, Pirastu said.  

One of the researchers involved in the study works for the coffee company Illy; however, the company did not provide funding for the study.

Originally published on Live Science.

A previously healthy 28-year-old man wound up in the emergency room with heart problems after drinking two energy drinks a day, as well as alcohol, for months, according to a new report.

The man experienced a very fast heart rate and an irregular heart rhythm (called arrhythmia), and the report supports a connection found in many previous studies: that there is a link between energy-drink consumption and heart problems.

Although the new report cannot prove that the energy drinks caused the man's abnormal heart rate, this case, combined with other previous reports, shows the abnormal heart rhythm "could be a complication" of energy-drink consumption, the researchers, from the University of Florida, reported in the July/August issue of the Journal of Addiction Medicine.

Given the popularity of energy drinks, doctors should consider asking patients about their energy-drink consumption if they have an unexplained heart rhythm problem, the researchers said. [5 Health Problems Linked to Energy Drinks]

Previous studies have found that consuming just one energy drink can increase blood pressure, sometimes to unhealthy levels. And there have been several reports of young people who have suffered heart attacks after consuming energy drinks, including a 2015 report of a 26-year-old who drank eight to 10 of these highly caffeinated beverages a day.

In the new report, the researchers wrote that the man went to the hospital after he started vomiting blood. He told the doctors that he had consumed two Monster energy drinks that day, each of which contained 160 milligrams of caffeine, for a total of 320 mg of caffeine that day. (For comparison, an 8-ounce cup of coffee contains about 95 to 200 mg of caffeine, according to the Mayo Clinic.) He also reported having consumed two to three beers that day.

A physical exam showed normal results, except that the man's heart rate was very fast — 130 beats per minute. (A normal heart rate is usually between 60 and 100 beats per minute.) A test of his heart's electrical activity showed he had atrial fibrillation, or an abnormal heart rhythm. The problem is not usually life-threatening, but it can increase the risk of stroke and other heart complications, according to the Mayo Clinic.

The man was treated with two heart medications (diltiazem and metoprolol), and his heart rate returned to normal within 24 hours. He was released from the hospital three days later, and as of one year after the incident, he had not experienced any more problems with his heart rhythm, the report said.

Monster energy drinks contain about four to five times the amount of caffeine per serving as caffeinated soft drinks. Caffeine can cause heart cells to release calcium, which may affect heartbeat, and high amounts of caffeine can cause heart palpitations and vomiting, the researchers said.

Between 2004 and 2012, the Food and Drug Administration received 40 reports of people experiencing health problems after drinking Monster energy drinks, including abnormal heart rate, increased blood pressure, loss of consciousness and cardiac arrest, the report said.

Still, up to 400 mg of caffeine per day is considered safe for healthy adults, according to the Mayo Clinic.

It's possible that other ingredients in energy drinks, along with caffeine, contribute to the development of heart problems, the researchers said. For example, taurine, a common ingredient in energy drinks, may heighten the effects of caffeine, the researchers said. Another ingredient, called guarana, also usually contains caffeine and may boost the caffeine content of the whole beverage above what's listed on the label, they said.

Further studies of the ingredients in energy drinks are needed for experts to better understand how the beverages may be linked with heart problems, the researchers noted.

Consuming alcohol along with energy drinks might also increase the effects of caffeine, allowing the compound to stay in the blood longer, the researchers said. Caffeine also could lower the sedative effects of alcohol, allowing people to continue drinking longer and consume more alcohol, which, in turn, could increase intoxication and lead to arrhythmias, they said.

Although the long-term effects of energy-drink consumption are not known, "it may be reasonable to limit their use, especially in combination with alcohol or illicit substances and in patients predisposed to arrhythmias," the researchers concluded.

At the time of publication, Monster Energy had not responded to an email request from Live Science for comment on the study.

Original article on Live Science.

Sports supplements, such as pre-workout and post-workout supplements, are not needed or even helpful for the vast majority of people who work out, several experts said. Only people who are really pushing themselves during a workout are likely to see a benefit from such supplements, experts said.

Many studies have found that caffeine can make a workout more effective, said Keith Baar, an exercise physiologist at the University of California, Davis, who studies the effect of macronutrients on exercise performance.

"Caffeine works in the brain to make you think that exercise is easier than it is," Baar said. "It is the number-one performance-enhancing drug. It works in everyone."

Another supplement with demonstrated effects is creatine. Muscles use this protein during the first 6 seconds of any exercise that requires explosive bursts of effort (such as one dead lift or one intense sprint), said Michael Ormsbee, the interim director for the Institute of Sports Sciences and Medicine at Florida State University, who has done extensive research on the effect of pre-workout supplements and nutrition on exercise performance. More than a dozen studies have shown that creatine may help exercisers put forth maximal exertion during strength training.

However, this effect typically requires a steady level of creatine in the muscle, so people who do this type of exercise should take creatine every day, to maintain adequate levels of the protein, said Jordan Moon, the program director of sports and health sciences and sports management at American Public and American Military University as well as the Chief Science Officer for the body composition and fitness tracking app FitTrace. But because most casual exercisers do not work out to exhaustion, any benefit they perceive from creatine is likely a placebo effect, Moon said.

The protein beta-alanine also appears to increase the levels of a protein called carnosine, which is needed for muscle contraction, according to a 2015 review in the journal Current Opinions in Clinical Nutrition and Metabolic Care. And according to the International Society of Sports Nutrition, beta-alanine supplementation for at least two to four weeks can improve performance in exercises that last 1 to 4 minutes. This can also generally reduce fatigue, particularly in older people, the study found.

But neither creatine nor beta-alanine makes much difference for performance in exercisers who are not working to exhaustion or muscle failure, both Moon and Baar said. Beta-alanine induces a tingly sensation, which makes people think, "oh, it's working," and that along with the placebo effect may spur them to work out harder, both experts said.

However, few workout supplements contain only creatine, caffeine or beta-alanine, but rather, may also contain sweeteners and other mystery substances, Baar said.

"For most people, the supplement is just going to be something that adds more calories," Baar told Live Science.

Original article on Live Science.

Caffeine — found in coffee, tea, soda and even chocolate — is the most widely consumed psychoactive substance on the planet. Used predominantly as a means to perk people up, the stimulant is legal and unregulated in most parts of the world. However, it's commonly thought that caffeine is responsible for some undesirable side effects, including dehydration.

The idea that caffeine can cause dehydration can be traced to a study performed in 1928 that noted increased urination in people who drank caffeinated beverages, and suggested that caffeine was a diuretic, according to Lawrence Armstrong, a professor in the Department of Kinesiology at the University of Connecticut and director of the Human Performance Laboratory. The idea spread, and caffeine's reputation as a dehydrating substance was solidified.

But science says it's a bit more complicated than that. [10 Things You Need to Know About Coffee]

"[T]he truth of the matter is, a small increase in urine output has little to do with dehydrating the body," Armstrong told Live Science.

He added that any increase in fluid input will lead to an increase in urine output. "If you drink a liter of water, [urination] will increase," Armstrong said. "Doesn't mean you shouldn't drink water."

In 2005, Armstrong and a team of researchers set out to put the myth to rest. They controlled the diets of 59 healthy males for 11 days, supplementing their daily consumption with body-mass-appropriate doses of caffeine, administered twice a day via capsule. Throughout the study, the researchers employed 20 different hydration biomarkers, such as urine volume and fluid-electrolyte balance, to assess dehydration.

While previous studies had investigated the effects of caffeine over short periods of time, Armstrong's research was the first to evaluate caffeine consumption for a continuous period longer than 24 hours.

The study found that the evaluated hydration indicators, including urine volume, were similar for all of the treatment groups. This finding demonstrates that caffeine does not have a dehydrating effect when compared to the control group (participants who received a placebo and did not consume any caffeine). The scientists also found that a higher dose of caffeine was no more likely to dehydrate a person than smaller doses were.

According to a 2016 investigation conducted by the University of Washington's Center for Public Health Nutrition, coffee remains the most significant source of caffeine in American diets. Though it doesn't cause dehydration, the stimulant has its share of purported side effects, including rumors that it may stunt people's growth or cause cancer. However, scientific research so far has not supported the idea that caffeine is bad for you, either.

"The fact that we don't have hospital emergency rooms filled [with patients] because they [drank] caffeinated beverages is clear evidence ... If there were negative health effects, [they] certainly would have been identified," Armstrong said. [10 Interesting Facts About Caffeine]

It is possible to consume too much caffeine, but Armstrong said the lethal dose is about 10,000 milligrams in a day. To put that number into perspective, the Mayo Clinic reports that an 8-ounce cup of coffee contains about 95 milligrams of caffeine. So, in order to overdose, you'd have to drink more than 100 cups of coffee in a day.

In fact, some scientific studies show that coffee actually has a number of health benefits.

"There's a lot more in a coffee bean than caffeine," Armstrong said. "The highest antioxidant intake among adults in America comes from coffee."

Research suggests that ingredients in coffee can protect against liver cancer, prevent the development of type 2 diabetes, lower blood pressure, and even combat dementia and depression, Science News reported.

Concerns about excessive caffeine consumption, particularly in children and adolescents, as well as harmful interactions with other drugs such as alcohol, require further research. But as it stands, your daily cup of joe isn't going to dehydrate you, and it might just have some added health benefits while getting you through your morning.

Original article on Live Science.

People who don't get enough sleep for several days in a row can't rely on caffeine to give them a mental boost, new research finds.

Researchers looked at 48 people who got only 5 hours a sleep a night, for five days in a row. Twice a day, participants took either a placebo, or 200 milligrams of caffeine, which is about the amount of caffeine in a big cup of coffee. The study was double-blinded, meaning neither the researchers nor the participants knew who got the caffeine or who got the placebo.

After three nights, the participants' alertness and their performance on a series of tests both fell, even after they'd had caffeine, the researchers found. [10 Interesting Facts About Caffeine]

"These results are important, because caffeine is a stimulant widely used to counteract performance decline following periods of restricted sleep," the lead author of the study, Tracy Jill Doty, a behavioral biology scientist at Walter Reed Army Institute of Research in Silver Spring, Maryland, said in a statement. "The data from this study suggests that the same effective daily dose of caffeine is not sufficient to prevent performance decline over multiple days of restricted sleep."

The results are among the first of their kind, Doty told Live Science. There is little research on how caffeine affects people who chronically get too little sleep, she said.

"This is particularly important information for the military, where war fighters may have restricted sleep and may also be using caffeine," she said.

In the study, the participants spent the week sleeping at the lab, and took either the placebo or caffeine at 8 a.m., and again at 12 p.m., each day. Then they took a series of tests related to mood, sleepiness, wakefulness and reaction time, Doty said. They also took cognitive tests hourly when they were awake.

Results showed that the caffeinated group had faster reaction times during the first two days compared with the placebo group, but not on the last three days of the experiment, Doty said. Moreover, the people who took caffeine reported feeling happier than those who took the placebo only on the first few days of the experiment.

"Over the final days of sleep restriction, those in the caffeine group rated themselves more annoyed than those in the placebo group," the researchers wrote in the study.

Doty called the findings "important," as they suggest that "the same amount of caffeine may not be effective in helping preserve performance under sleep loss."

However, the study didn't take into account that sleep-deprived individuals might increase their caffeine intake over time, Doty said.

"We do not know what would occur if more caffeine was taken," she said. "Increased caffeine dosage will increase negative side effects such as jitteriness, but we do not currently know if an increased dosage would prevent performance decline."

The unpublished study was presented Tuesday (June 14) at Sleep 2016, a meeting of the Associated Professional Sleep Societies, in Denver.

Original article on Live Science.

If you are a pet owner, you might have been tempted to spoil your furry family member with a treat from your plate. But before you do, make sure you're not sharing one of the common foods that can cause serious, and sometimes fatal, medical problems for cats and dogs.

In a new review of studies, two animal health researchers in Italy drew up a list of the foods that are the most common culprits in pet poisonings worldwide.

"Several foods that are perfectly suitable for human consumption can be toxic to dogs and cats," the researchers wrote in their review, published in the journal Frontiers in Veterinary Science. "The poisoning episodes are generally due to lack of public knowledge of the serious health threat to dogs and cats that can be posed by these products."

Sometimes, owners give these harmful foods to their dogs and cats, but a lot of times, pets accidentally ingest these foods, which happen to be commonplace in homes. The researchers found that, in the past decade, reported cases of pet poisoning have involved chocolate and chocolate-based products, plant foods in the Allium genus (including onions, garlic, leeks and chives), macadamia nuts, Vitis vinifera fruits (including grapes, raisins, sultanas and currants), foods sweetened with xylitol (such as sugar-free chewing gums and cookies), ethanol in alcoholic beverages, and unbaked bread dough.

The list of human foods that are toxic to cats and dogs continues to grow as cases get reported. And in many instances, scientists don't know the exact biological reasons why certain foods sicken animals. [10 Things You Didn't Know About Dogs]

"While some foodstuffs, such as chocolate, have long been known to cause poisoning in dogs and cats, others, such as grapes, had previously been considered unlikely to cause problems, and have emerged as a potential concern only in the last few years," the authors of the review, Cristina Cortinovis and Francesca Caloni, of the University of Milan in Italy, wrote in their paper. And as a result, poisoning cases have sometimes been wrongly diagnosed, they said.

In general, dogs are affected more than cats, in part because they eat pretty much anything, whereas cats are somewhat protected because they're pickier eaters, the researchers found.

Here's an outline of what's known about foods that are toxic to dogs and cats, according to the review:

Chocolate, coffee and caffeine

Chocolate has a dark side: Cocoa-based products are the items most commonly involved in food poisoning in pets, causing anything from mild problems such as tummy aches to seizures and death. These "poisoning episodes frequently occur around holidays, when there is a higher occurrence of chocolate products in the home," the researchers wrote.

Chocolate contains two compounds that are toxic to pets: theobromine and caffeine, the researchers said. These compounds alter cellular processes and result in the stimulation of both the central nervous system and heart muscles. Depending on the type of chocolate (dark chocolate has more theobromine than lighter chocolate), one small piece can be enough to make a small dog sick. [10 Interesting Facts About Caffeine]

Theobromine and caffeine are also found in other types of products. Poisoning cases have been reported after the ingestion of herbal supplements, garden mulch made of cacao bean shells, caffeine tablets and caffeine-containing bait, according to the review.

Initial symptoms often occur within 2 to 4 hours after ingestion and include restlessness, excessive thirst, urinary incontinence and vomiting. "Dogs can be in an excited state," and have a fever or rapid heart rate, the researchers said. If the animal gets prompt treatment, it often can recover well, but delaying treatment can result in seizures, coma and even death from abnormal heart rhythm or respiratory failure.

Xylitol

The next most common toxic foods for pets are products sweetened with an artificial sweetener called xylitol. Xylitol isfrequently used in products such as sugar-free gum, candy, bread and other baked goods. Xylitol is also found in dental care products (for both people and pets) because of its antibacterial properties.

"Dogs are the species at risk of developing severe, life-threatening clinical signs," the researchers wrote. In dogs, xylitol stimulates the release of the hormone insulin, leading to a dangerous decrease in blood sugar levels.

Symptoms of xylitol poisoning may develop within 30 to 60 minutes of ingestion, but they also may occur up to 12 hours later. These symptoms include vomiting and signs of hypoglycemia (low blood sugar), such as lethargy, inability to control movements, collapsing and seizures.

Onions, chives, garlic and leeks

Plant species in the Allium genius — such as onions, chives, garlic and leeks — often make dogs and cats sick. These common ingredients contain compounds called organosulfoxides. When the animal chews the plant, the organosulfoxides are converted into a complex mixture of sulfur compounds, which can cause the animal's red blood cells to break down. If the dog or cat ingests even just a piece of an onion (specifically, 5 grams of onion per kilogram of body weight for cats, or 15 to 30 grams per kg for dogs), it can cause dangerous changes to their blood.

According to the review, between 1994 and 2008, there were 69 reported cases of dog poisonings and four cases of cat poisonings from Allium foods. The cases included a range of different foods: raw and baked garlic, Catalan spring onions (commonly known as "calcot"), onion soufflé, butter-cooked onions and steamed dumplings containing Chinese chives. Onions and other Allium plantsmaintain the compounds that cause their toxic effects even after being cooked or dried, the researchers added. [6 Secrets to Unlocking Your Cat's Personality]

Usually, cats and dogs ingest these foods accidentally, but there was one reported case in which an owner intentionally fed a dog a large quantity of raw onions. While some pets may not show any symptoms after ingesting Allium foods, there have been cases of fatal poisonings.

Symptoms of Allium poisoning may appear a day or several days after consumption, depending on the amounts ingested. Common initial signs include vomiting, diarrhea, abdominal pain and loss of appetite. The affected animals develop anemia, and show symptoms such as weakness, rapid breathing, high heart rate, pale color in mucous membranes and reddish or brown urine.

Alcohol

Ethanol, or alcohol, poisoning in small animals generally occurs when an animal accidentally ingests an alcoholic beverage. However, cases of alcohol poisoning in dogs have been reported after dogs have ingested rotten apples, sloe berries used to make sloe gin, and uncooked bread and pizza dough, all of which contain the compound.

When pets digest ethanol, it gets rapidly absorbed from the gastrointestinal tract and reaches the brain, just as it does in humans. Within an hour, the animals may show depression, loss of movement control, lethargy, sedation and high body temperature. Animals may go into a coma and develop a dangerously slow breathing rate. In most of the reported cases, the affected pets recovered after receiving treatment and supportive care.

Ethanol isn't found only in foods and beverages, however. Paint and varnish, medication, perfume, mouthwash and certain types of antifreeze also contain the compound.

Grapes and their dried products (raisins, sultanas and currants)

Grapes, raisins, sultanas and currants in both raw and cooked forms (including those found in snack bars and baked goods) have been reported to cause kidney failure in dogs. However, not all dogs have the same reactions to these foods, according to the review.

In a recent study that looked at 180 case reports involving dogs' ingestion of grapes and related fruits, some animals didn't show any symptoms after eating 2 lbs. (0.9 kg) of raisins, while others died after eating just a handful. Dogs that develop symptoms may show signs such as vomiting, diarrhea, loss of appetite, lethargy and abdominal pain within 24 hours of ingesting the grape products.

Hops

Hops are commonly used for brewing beer, and have become more of a risk to pets as more and more people pick up home brewing as a hobby, according to the review.

Hops contain a variety of compounds — including resins, essential oils and tannins — which can lead to fever when pets ingest them. Other symptoms include anxiety, rapid heart rate, panting, vomiting, abdominal pain and seizures. The affected animals may show symptoms within hours of eating hops. The risk of death can remain high even after the animal is treated for fever. [Here, Kitty, Kitty: 10 Facts for Cat Lovers]

Macadamia nuts

Macadamia nuts are popular and healthy snacks for humans, but they can poison dogs. It's not clear how much of these nuts, when ingested by dogs, can cause serious problems. However, some reports indicate that the ingestion of as little as 0.7 grams per kg of nuts is enough to cause symptoms.

Symptoms of macadamia-nut poisoning develop within 12 hours and may include weakness (particularly hind-limb weakness), vomiting, inability to control movements, shaking, fever, abdominal pain, stiffness and pale mucous membranes. Macadamia-nut poisoning may not be very common, but in just five years, more than 80 cases were reported just in Queensland, Australia, a major area for macadamia-nut cultivation. No pet deaths resulting from macadamia-nut ingestion have been reported to date, and animals are expected to fully recover within a day or two with minimal treatment, the researchers wrote.

Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

NEW ORLEANS — Women who love their coffee, take note: The brewed beverage is associated with a reduced risk of endometrial cancer, a new study finds.

In the study, researchers found that women who drank more than four cups of joe a day had a 22 percent lower risk of developing endometrial cancer, which is cancer of the lining of the uterus, than non-coffee drinkers.

Endometrial cancer is the most common gynecological cancer, according to the study, presented here yesterday (April 18) at the American Association for Cancer Research's annual meeting. Other gynecological cancers include cervical cancer and ovarian cancer.

The results show that there is an association between coffee intake and endometrial cancer risk, said Marta Crous-Bou, a research fellow in medicine at Harvard Medical School in Boston and the lead author on the study.

In particular, the researchers found that drinking coffee is a protective factor for this type of cancer, Crous-Bou told Live Science. [Coffee's Perks: Studies Find 5 Health Benefits]

To determine the effects of coffee on a woman's risk of developing endometrial cancer, the researchers looked at data from 19 previous studies. About 40,000 women were included in the studies, including about 12,000 who had been diagnosed with endometrial cancer, and about 28,000 who had not, to serve as controls.

While drinking more than four cups of coffee a day was associated with the greatest benefit, drinking two to three cups was also associated with a reduced risk of the cancer, Crous-Bou said. Women who drank two to three cups a day had a 7 percent lower risk than those who didn't drink any coffee, according to the study.

After factoring in a woman's body mass index (BMI), the researchers found that coffee's protective effects were only seen in women whose BMI indicated they were overweight or obese, Crous-Bou said. Women with a normal-weight BMI didn't benefit from drinking coffee, she said. (A higher BMI is a strong risk factor for endometrial cancer, she added.)

As for the caffeine question, the answer is yes — caffeine appears to count. Not all of the studies asked the women to specify whether they drank caffeinated coffee or decaf, but when the researchers looked at those that did, they found that only caffeinated coffee was associated with a statistically significant decrease in risk.

While this study didn't specifically look at the mechanism that might explain the association, researchers think that certain compounds in coffee may decrease levels of estrogen and insulin, Crous-Bou said. Both estrogen and insulin have been shown to play a role in the development of endometrial cancer, she said. [7 Cancers You Can Ward Off with Exercise]

Coffee was not the only beverage included in the study — the researchers also looked at how tea intake may affect endometrial cancer risk. However, they found no association for tea, Crous-Bou said.  

The findings have not been published in a peer-reviewed journal.

Follow Sara G. Miller on Twitter @SaraGMiller. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

NEW YORK — Coffee has been linked to a slew of health benefits, and now, a new study suggests that it may improve reaction time in older adults.

In the study, presented today (April 5) here at the Cognitive Neuroscience Society's annual meeting, researchers set out to examine the effects of caffeine on a number of cognitive abilities in healthy, older adults.

Ultimately, their goal is to see what role caffeine may play in treating dementia, said Kanchan Sharma, a neurology researcher at the University of Bristol in England and the lead researcher on the new study. [10 Interesting Facts About Caffeine]

Currently, some treatments for dementia work by boosting attention, Sharma told Live Science. Caffeine is also thought to boost attention, but interestingly, this hasn't been proven in research, he said.

To study the effects of caffeine on attention, Sharma and his colleagues tested 38 healthy adults who ranged in age from 55 to 91, Sharma said.

The participants first took a series of tests that measured different aspects of attention. Then, the participants were asked to stop drinking caffeine for one week. After one week, one group was given 100 milligrams (1 cup) of caffeinated coffee, and the other group was given decaffeinated coffee, and they were asked to perform the tests again. The next day, the drinks were switched. This way, the participants could serve as their own controls, Sharma said.

The researchers found that drinking the caffeinated coffee improved the participants' average reaction time. They also found that the caffeine improved participants' accuracy on a test called the "Stroop test," which measures skills such as planning and focusing.

In the Stroop test, participants are shown the name of a color, but the name is written in a different color. For example, the word "blue" may be written in red text. The participants are then asked to identify either the name of the color, or the color of the text.

Drinking caffeine had no effect, however, on the participants' motor speed, or how quickly they could press a button when prompted.

Sharma noted that the improvements the researchers observed in the study were small. However, in people with cognitive impairment, caffeine could have a much greater effect because their baseline would be lower, Sharma said. In future studies, Sharma plans to look at the effects of caffeine on people who have cognitive impairments, such as dementia, he said.

The findings have not been published in a peer-reviewed journal.

Follow Sara G. Miller on Twitter @SaraGMiller. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Nectar of the Gods or Poison?

Coffee is one of the world's most widely consumed beverages, yet it's effects are still debated. Scientists and epicurians have long made claims about this fragrant brew. Will it kill you or make you live longer? What makes the perfect cup? Is decaf really decaf? And who enjoyed the first cup of java?

Find scientific answers to these questions and more inside.

Editor’s Note: This article, originally published in 2013, was updated in March 2016 to reflect the latest news, research and new facts.

1. Caffeine Can Kill You

Despite its known plusses, coffee can be deadly. But you'd have to drink 80 to 100 cups in a hurry, health experts say. We advise not trying. In September 2015, the FDA warned of the dangers of powdered caffeine, a potent product that had recently burst into popularity.

2. Coffee Can Be Good For You

A plethora of separate studies in 2014, 2015 and 2016 found coffee is good for your liver, may lower risk of heart attacks, might cut the risk of colon cancer and, as reported in the journal Circulation, one to five cups a day may generally reduce the risk of early death. A study released in March, 2016 found coffee associated with a reduced risk of multiple sclerosis (MS).

3. Caffeine Might Boost Female Sex Drive

It worked on rats anyway. But researchers say in humans, coffee might enhance the sexual experience only among people who are not habitual users.

4. Caffeine Might Cut Pain

Moderate doses of caffeine — the equivalent of two cups of coffee— can cut post-gym muscle pain, a small study found. But the research was done on people who were not regular coffee drinkers. A study in 2012 found those who drink coffee before sitting down to work at a computer had less neck and shoulder pain. There is not sufficient research, in big enough studies, to draw any firm conclusions on this possibility, however.

5. Caffeine Can Indeed Keep You Up at Night

Health experts advise avoiding coffee for 6 hours before bedtime, since the effects of caffeine can last hours. A 2015 study found caffeine can confuse your body’s internal clock, confusing the signals that tell you when to sleep. Night shift workers may find coffee during work hours disrupts their daytime sleep, another study found.

Decaf coffee has caffeine!

6. Decaf Coffee Has Caffeine!

Hey, what?! Yep: If you drink five to 10 cups of decaffeinated coffee, you could get as much caffeine as from one or two cups of caffeinated coffee, a study found.

7. Decaffeination Uses Chemicals

Beans are steamed, so that dissolved caffeine rises to the surface, where it is washed off using an organic solvent called methylene chloride.

Related: How Is Decaf Coffee Made?

8. Caffeine Is Not The Bitter Culprit

Caffeine is not the main bitter compound in coffee. Rather, the pungent perpetrators are antioxidants.

Next Up: It's all in the roasting

9. Great Coffee Depends on Roasting and Brewing

When it comes to great flavor, coffee chemistry boils down to roasting and brewing. During roasting, oil locked inside the beans begins to emerge at around 400 degrees. The more oil, the stronger the flavor. Caffeine content goes up as the water spends more time in contact with the grounds, so regular coffee often has more of it than espresso or cappuccino. Darker roasts also yield more caffeine.

Finally: Why goats are so important (really!)

10. Coffee Was Discovered by Goats

A millennium ago on a mountainside in Africa, a herd of goats kept a shepherd up at night after feasting on red coffee berries. The shepherd took his animals' discovery to some monks, and very long prayer sessions ensued. It's a good story, anyway.

Bonus facts, since you made it all the way: A study shows that Americans get most of their antioxidants from their daily fix of java. One to two cups a day appear to be beneficial. Or, if you don't like coffee, you could try black tea, the second most consumed antioxidant source. Bananas, dry beans, and corn wrap up the top five.

Double bonus fact: Yes, coffee can help you poop, but scientists don’t really know why!

Couples who wish to get pregnant may want to avoid caffeine because it's associated with an increased risk of miscarriage, a new study from the National Institutes of Health (NIH) suggests.

For women, drinking more than two caffeinated drinks daily before getting pregnant was associated with a 74 percent higher risk of a miscarriage, according to the study published today (March 24) in the journal Fertility and Sterility. 

But women's caffeine consumption wasn't the only factor: Among couples in which the male partner drank more than two caffeinated beverages daily before conception, there was a 73 percent higher risk of a miscarriage, according to the study. [6 Myths About Miscarriage]

"Our findings indicate that the male partner matters, too," Germaine Buck Louis, the director of Intramural Population Health Research at the National Institute of Child Health and Development and lead author on the study, said in a statement. "Male pre-conception consumption of caffeinated beverages was just as strongly associated with pregnancy loss as females'," Buck Louis said.

The study included 501 couples in Michigan and Texas who had stopped using contraception and were trying to become pregnant. The couples were instructed to keep daily journals of their lifestyle behaviors, including smoking cigarettes and drinking alcohol and caffeinated beverages, according to the study. Couples who got pregnant within a year continued in the study until they gave birth or experienced a miscarriage, according to the study.

Of the 344 couples who became pregnant, 98 experienced a miscarriage, according to the study. Women 35 and older were nearly twice as likely to miscarry as women younger than 35, according to the study.

In addition to the caffeine findings, the researchers also found that women who took a daily multivitamin before and during pregnancy were less likely to have a miscarriage. Women who took a daily multivitamin before getting pregnant were 55 percent less likely to miscarry, according to the study. And women who continued to take the multivitamin during early pregnancy had a 79 percent lower miscarriage risk, according to the study.

The protective effect from the multivitamin may come from the folate and vitamin B6 found in a multivitamin, both of which have been linked to decreased risk of miscarriage, according to the study.

The study only showed an association between caffeine intake and miscarriage, and did not prove cause and effect. Previous studies have shown similar results, although the potential mechanism is still unknown, according to the study.

The authors did note, however, that the findings of the study do not necessarily mean that drinking decaf instead of regular coffee is safer, as the study did not include information on decaffeinated drinks, they wrote. 

Couples may want to limit their caffeine intake to fewer than three daily beverages, and women should continue to to be advised to take daily multivitamins before and during pregnancy, the researchers wrote in their conclusion.  

Follow Sara G. Miller on Twitter @SaraGMiller. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Brew up another pot of joe: Drinking coffee (and a lot of it) is associated with a reduced risk of developing multiple sclerosis (MS), a new study finds.

Compared with people who said they never drank coffee, people who reported drinking large amounts of java were nearly a third less likely to develop MS, according to the study.

"We observed a significant association between high consumption of coffee and decreased risk of developing MS," the researchers, led by Anna Hedström, a doctoral student in environmental medicine at the Karolinska Institute in Sweden wrote in the meta-analysis study, published today (March 3) in the Journal of Neurology, Neurosurgery & Psychiatry.

The results of the study were previously presented in February 2015 at the annual meeting of the American Academy of Neurology, but this is the first time they have been published in a peer-reviewed scientific journal.

In the study, the researchers looked at the results of two large case-control studies, which included 2,779 people with MS and 3,960 people without MS. The researchers found that those individuals who reported the highest levels of coffee consumption (more than 4 cups [900 mL] a day) had a 29 percent lower risk of MS than those who reported drinking no coffee. [Coffee's Perks: Studies Find 5 Health Benefits]

The study showed an association, and not a cause-and-effect link between drinking lots of coffee and a lower risk of MS. But it's possible that caffeine has a protective effect on the brain and spinal cord, the study said. In people with MS, the body's immune system attacks the protective covering, called myelin, that surrounds nerve fibers. This damage makes it difficult for the brain to communicate with the rest of the body, resulting in symptoms such as muscle weakness, poor coordination, blurred vision and pain.

However, the researchers cautioned more studies are still needed. The scientists also noted that their analysis does have limitations, including that people were asked to recall their coffee intake, which could lead to errors.

Although previous studies looking at the link between coffee and MS have had mixed results, with some studies showing a benefit and others showing none, the current meta-analysis is notable in part for its large sample size and international group of participants, said two neurologists who were not involved in the study, but wrote an editorial accompanying it in the journal.

There are "well-known challenges that exist in untangling the nature of associations between dietary factors and disease risk," and therefore, "these inconsistencies are not surprising," wrote José Maria Andreas Wijnands and Elaine Kingwell, both neurologists at the University of British Columbia in Canada.

"Although it remains to be shown whether drinking coffee can prevent the development of MS, the results of these thorough analyses add to the growing evidence for the beneficial health effects of coffee," the editorial authors wrote.

Indeed, the once-maligned beverage has been linked to numerous health benefits in recent years, including a lower risk of heart attacks, melanoma and even early death. Coffee has also been linked to improved liver health. 

Follow Sara G. Miller on Twitter @SaraGMiller. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Say good-bye to those mornings spent waiting in line at the local coffee shop: A new mobile brewing device that looks like an everyday thermos could help coffee lovers make — and enjoy — their caffeine fix on the go.  

The "mojoe," short for "mobile cup of joe," is a portable coffeemaker that doubles as a travel mug. The handy device offers few outward clues to its coffee-brewing prowess, aside from a couple tiny on/off LED lights, a charging port and a slightly elongated shape.

Even midbrew, the mojoe stays incognito; it doesn't make the burbling and gurgling noises that a regular coffee pot makes. "What you may hear is just a little bit of bubbling right before it's about to siphon," said Joseph Hyman, inventor of the mojoe and CEO of MoJoe Brewing Co. "It's very, very low noise." [10 Interesting Facts About Caffeine]

Hyman first dreamed up what would become the mojoe when he was a college student studying late at night in the library. He didn't want to leave his spot and dish out money to buy a coffee from the shop in the library's lobby, and he knew if he returned to his dorm room, he'd lose motivation to trek back to the library. So, he thought, "Why isn't there a mobile coffeemaker?" he told Live Science.

The mojoe is the first of its kind, Hyman said, because unlike other portable coffeemakers on the market, the mojoe does not require you to heat water before brewing, and it can withstand superhot temperatures. To create a self-contained coffee-brewing system within a travel mug, Hyman and his team figured out how to combine aspects of drip brewing with vacuum brewing in a small, light and durable device.

Most conventional coffeemakers are drip brewers that involve pouring hot water over ground coffee beans. Vacuum brewers, on the other hand, look more at home in a chemistry lab than on a kitchen stove. A vacuum brewer often has a clear, hourglass-shaped chamber suspended in space by a metal grip extending from a thin but sturdy stand. Water sits in the bottom bulb of the hourglass until it gets hot enough to convert to water vapor. This vapor expands in the bottom bulb until running out of room, building up enough pressure to push hot water up through a glass siphon connecting the bottom and top bulbs. Once the vapor reaches the upper bulb, which contains coffee grounds, the hot water mixes with the grounds and turns into coffee. When the coffee is fully brewed, the stove is shut off, the vapor condenses and the brewed coffee falls back into the bottom bulb.

The mojoe also harnesses water-vapor pressure to energize and move water, but the device relies on drip brewing to actually make coffee. "We used science to do two things," Hyman said, namely to move water and turn that water into coffee. The patented system in the mojoe is called VacDrip.

Similar to a vacuum brewer, the VacDrip system heats water,turning it into a vapor that gets siphoned into a different chamber. However, unlike in a vacuum brewer, the two chambers in the mojoe are side-by-side rather than on top of each other. [5 'Hidden' Sources of Caffeine]

With the mojoe, water begins in a center compartment that runs the length of the mug. The water is heated using power from the mojoe car adapter, a wall-plug adapter or a rechargeable battery. Once the water is heated to 200 degrees Fahrenheit (93 degrees Celsius), the water vapor starts to push hot water up through a siphon in the middle of the compartment. When the water reaches the top of the mojoe, the siphon deposits the water into a mesh basket of coffee grounds. Water seeps in the basket and then drips out as coffee, just as it would in a drip brewer, Hyman said. The freshly brewed coffee fills the space between the center compartment and the wall of the mug.

The correct brewing temperature for coffee is 200 degrees Fahrenheit, and, "coincidentally, right around 200 degrees is when water starts to produce a lot of water vapor," Hyman said. "Once all the water comes out, you hear a very low "schuuuuu," and that's the vapor pressure releasing," he added. Only about 5 to 10 percent of the water will turn into vapor during the brewing process; vapor is the vehicle that moves the water, Hyman said.

Any part of the mojoe that comes in contact with 200-degree-Fahrenheit water is made of superdurable plastic called HDPE, or high-density polyethylene, Hyman said. HDPE is a popular material for kitchen gadgets, and therefore it's washable and resistant to sticky foods, he added. To attach the various parts of the mojoe, Hyman and his team had to find a special food-grade adhesive that could both bind to HDPE and resist heat.

"This whole thing was an engineering challenge," Hyman said. Not only were the materials tricky to assemble, but also the power source had to be strong enough to transform water. "Water is such a great insulator, and it requires a lot of joules [energy] to heat water," Hyman said. "It doesn't want to get hot."

The mojoe can be powered directly through an outlet or with a car charger, Hyman said. The mojoe also has a battery pack that takes about 20 to 30 minutes to charge. With the battery pack, the mojoe weighs about 1.3 lbs. (0.6 kilograms); without the battery, it weighs 0.7 lbs. (0.3 kg). The mojoe can hold up to 8.5 ounces (250 milliliters) of liquid and can brew tea and hot chocolate in addition to coffee.

The mojoe raised $85,860 through a crowdfunded Kickstarter campaign and can currently be pre-ordered only through the MoJoe Brewing Co. website. Hyman said he expects the mojoe will be ready to ship in May.

Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

You can now add coffee to the growing list of foods and drinks that are available as products infused with marijuana.

Several companies have started selling cannabis-laced coffee, claiming to give users an added "buzz" to their cup of joe.

But what happens when you combine two psychoactive substances: marijuana and caffeine?

The effects of using these two substances in combination have not been heavily researched, said Dr. Scott Krakower, the assistant unit chief of psychiatry at Zucker Hillside Hospital in New Hyde Park, New York. But using two drugs in combination can always potentially be a problem, he said.

There is some evidence from lab and animal studies that suggests that taken together, caffeine and marijuana "would mix, neuro-chemically," Krakower told Live Science. In other words, they would have different effects when used together then you'd expect from looking at the effects that each compound has when used alone.

For example, it appears that the combination of caffeine and THC (the compound in marijuana responsible for its psychoactive effects) may worsen a person's working memory, Krakower said. This is counterintuitive, as other research suggests that caffeine may contain cognitive-enhancing properties, he said. There seems to be some sort of compounding when the two chemicals are taken together that works against you, he said.

There's also the issue of taking a stimulant (caffeine) and a depressant (marijuana) at the same time, he said.

The combination of the two will likely make the user feel wired and tired at the same time, he said. But taking caffeine with marijuana would not cancel out the high induced by the drug, he noted. And it would be a mistake to think that someone could get high and then sober up, thanks to the caffeine, Krakower said.

The potentially harmful cognitive effects of the combination are concerning, he said.

Much more research is needed into the subject, however, Krakower added. [The Drug Talk: 7 New Tips for Today's Parents]

With the legalization of marijuana in some states, edible products are growing in popularity. Some experts are concerned that these products may lead users to consume more THC than they intend to, because the onset of the drug's effects are slower when it is ingested as opposed to smoked — as they wait, users may eat more, to feel an effect.

In addition, labels on products containing THC may not be accurate. In a 2015 study published in JAMA, researchers found that only 13 out of 75 edible marijuana products had labels that accurately listed the product's levels of THC.

Follow Sara G. Miller on Twitter @SaraGMiller. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Everyone wants to get the most out of the time they spend exercising, and "preworkout" supplements claim to help you do exactly that. It might be tempting to try one of these supplements before hitting the gym or heading out for a run, in hopes of increasing your energy levels, muscle power or endurance during your workout.

Preworkout supplements often contain a mystery blend of ingredients ranging from caffeine to guarana to creatine. But do these supplements work, and are they safe to take?

It turns out that these supplements may just change the way you feel while you're working out. Many of the ingredients in preworkout supplements are intended to give athletes the perception that their workout is supercharged, said Jordan Moon, an exercise physiologist and sports nutritionist at the United States Sports Academy and Concordia University Chicago, and chief science officer at the fitness tracking website Fittrace.com.

"You've got ingredients that are going to increase blood flow, increase heart rate, increase focus, increase blood flow to the skin and give you a little tingle," Moon told Live Science.

But those physical effects don't make people bigger, stronger or faster, Moon said.

And although some of these supplements' ingredients — such as caffeine, creatine and beta-alanine — have been shown to modestly enhance performance in extreme athletes and bodybuilders, they only give people an edge if they are pushing themselves to the limit, Moon said.

And some supplements on the market may contain illegal and dangerous additives, such as amphetaminelike stimulants. Even supplements that contain only legal ingredients can include high levels of caffeine, which can have a negative effect on the heart, recent testing by one independent lab found. [Macho Man: 10 Wild Facts About His Body]

Caffeine rush

Several studies have shown that taking caffeine can provide a physical boost before a workout. For instance, a 2012 study in the Journal of Strength Conditioning and Resistance found that men who took caffeine supplements could deadlift, bench-press and do other heavy lifting at greater weights compared with men who took a placebo. Other studies have suggested that runners and rowers can increase their aerobic capacity with a dose of caffeine, although the studies noted that the benefits of caffeine tend to wane as people develop a tolerance to it.

However, too much caffeine can pose a health risk, and supplements can contain much more than is found in food or drinks. A person could guzzle gallons of coffee and not suffer from a true caffeine overdose. But even at much lower levels, caffeine can worsen underlying conditions such as a heart arrhythmia, leading to cardiac arrest.

In recent testing, the supplement testing company LabDoor looked at 45 popular preworkout supplements and found that many contained extremely high doses of caffeine. One supplement contained 435 milligrams of caffeine — almost as much as four cups of coffee. (The research has not been published in a peer-reviewed journal, meaning it has not gone through the standard process used to vet scientific findings. LabDoor also links to sites such as Amazon and The Vitamin Shoppe, where consumers can purchase the supplements, and receives a commission on those sales.)

Although the lab found that none of the supplements contained a dose of caffeine that would be dangerous on its own, combined with a few cups of coffee or a soda, the supplements could easily make someone feel shaky, nauseated and ill, and could also exacerbate underlying heart conditions, said Neil Thanedar, CEO of LabDoor.

"The whole point [of these supplements] is to work out harder or more intensely," Thanedar told Live Science. So supplements with high caffeine levels are "putting you at risk of heart issues, and then telling you to go out and exert yourself."

However, Moon said the levels in most of these products are unlikely to be truly dangerous.

"Unless you're taking twice the dose or like four times the dose, you're still going to be at the safe maximum recommended amount of caffeine," Moon said. [How to Do the 7-Minute Workout]Creatine and amino acids

Almost all preworkout supplements contain creatine, which seems to boost energy production in muscle cells and also seems to draw fluids from the blood plasma into the skeletal muscle, which can improve muscle performance.

Creatine supplementation has shown modest benefits in a few small trials. A 2003 study in the Journal of Athletic Training found that college football players taking the supplement had less cramping and dehydration, as well as fewer injuries, than players who took a placebo. And a 2002 study of 20 athletes in the journal Nutrition found that creatine increased their body mass and gave them peak power during short sprints.

However, creatine must be taken regularly in order to "build up" to sufficient levels, Moon said. Taking it once or twice a week before a workout will not produce the necessary level to have an effect, and it only works when people push themselves hard during a workout. 

Most "people who go to the gym spend 90 percent of the time talking and resting over lifting," Moon said. "They might not even be pushing themselves hard enough to get any of the effectiveness of the ingredients."

LabDoor's testing showed that the labels of most supplements that were found to contain creatine did not list the amounts of creatine they contained. Moon noted that LabDoor did not test one of the most popular preworkout supplements, Jim Stoppani's 12-Week Shortcut to Size.

Moon also said that grading supplements based on testing the levels of their ingredients may be misleading because there's no good research on what dose may be effective for many of the supplement ingredients, some of which act synergistically. And consumers should know that supplement makers often tweak their products' formulations every four or five months, so testing from companies like LabDoor will always be "playing catch-up" with these products, Moon added.

Other common preworkout ingredients include the B vitamin niacin, which can cause sweatiness and blood flow to the skin called a "niacin flush," and vasodilators, such as citrulline, which widen blood vessels. Although studies don't show that these ingredients increase muscle mass per se, the increased blood flow to the muscles may make "your muscles feel pumped, and you look bigger when you're working out," Moon said.

The effect, however, is transient, he said.

Realistically, "the only time people really need to take a preworkout [supplement] is if their nutrition is non-ideal and they need help to get some energy," Moon said. For example, that may include a wrestler who's trying to fit into a lower weight class but still needs to work out, or someone on a low-carb diet who's still trying to bulk up, he said.

Proprietary blends

Either way, there's little evidence that the "proprietary blends" of ingredients that are found in preworkout supplements — which can be a grab bag of up to 10 ingredients — help boost athletic training any more than the individual ingredients alone. A randomized, controlled study published in 2014 in the Journal of Sports Science and Medicine found that athletes who took a supplement called SizeOn Maximum Performance performed no better than athletes taking a combination of protein, carbohydrates and creatine.

But by positioning their products' unique recipes as a trade secret, supplement makers circumvent the need to label each product with the dose of each individual ingredient, meaning a given supplement may have too little creatine, for instance, to have an effect, Thanedar said.

Dangerous additions

The biggest potential risk associated with preworkout supplements is the inclusion of dangerous substances, according to both Thanedar and Moon. For instance, the Food and Drug Administration recently filed criminal charges against USPLabs, the makers of the preworkout supplements Jack3d and OxyElite Pro, which have been linked to acute liver damage and multiple deaths.

The FDA found that the supplements contained a dangerous amphetamine precursor called 1,3-dimethylamylamine, or DMAA, which is not on the FDA's list of approved supplement ingredients.

LabDoor's testing revealed that the newer formulations of these supplements do not contain the illegal DMAA. However, another supplement, a drink called Train Critical FX, contained a similar amphetamine precursor, called BMPEA (beta-methylphenethylamine), the testing showed. BMPEA is a doping agent that can bring heart risks, and is also not on the FDA's list of approved supplement ingredients.

"This ingredient, as well as other stimulants, really have no business being in the dietary supplement marketplace," said Andrea Wong, vice president of scientific and regulatory affairs at the Council for Responsible Nutrition, a trade organization for the supplement industry.

Ultimately, while most preworkout supplements are probably not dangerous, there's little scientific backing for some of their more overblown claims.

"In the supplement industry, it's about marketing; it's not about what's in the product," Moon said. "Supplements don't really do that much unless you're already doing a lot on your own."

Follow Tia Ghose on Twitter and Google+. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Pregnant women, perk up! It's okay to indulge in your morning cup of coffee without worrying about it affecting your child's IQ, a new study finds.

In the study, researchers found that children born to women who consumed caffeine while pregnant did not have lower IQs or more behavior problems than those born to women who didn't indulge in coffee.

There was no evidence that caffeine consumption during pregnancy has a negative effect on children's cognition or behavior at ages 4 or 7, researchers wrote in their study, published yesterday (Nov. 19) in the American Journal of Epidemiology.  [5 Experts Answer: Is Caffeine Bad for Kids?]

"Taken as a whole, we consider our results to be reassuring for pregnant women who consume moderate amounts of caffeine, or the equivalent to one or two cups of coffee per day," Sarah Keim, an assistant professor of pediatrics and epidemiology at The Ohio State University College of Medicine and co-author of the study, said in a statement.

In the study, the researchers analyzed the amount of a compound called paraxanthine in blood samples from 2,197 pregnant women at two points during their pregnancies. (When you consume caffeine, the body breaks it down into several compounds, including paraxanthine.) The samples were collected as a part of the Collaborative Perinatal Project, a 25-year study that explored the links between pregnancy and perinatal factors and children's health. The researchers compared the paraxanthine levels with the children's IQ and behavior when they were 4 and 7 years old.

The samples were collected between 1959 and 1974, a period when drinking coffee during pregnancy was more common, the researchers noted in their study. This provided the researchers with a wider range of caffeine-intake levels than if the research had been conducted today, the investigators wrote in their study.

This is not the first study to suggest that drinking coffee in moderation may be safe during pregnancy.

In a 2012 study, researchers found that there was no link between moms' caffeine habits and whether babies woke up at night.

In addition, the American College of Obstetricians and Gynecologists has stated that it considers moderate caffeine consumption — defined as less than 200 milligrams per day, the amount in about one or two cups of coffee — to be safe during pregnancy. The group notes, however, that the effects of large amounts of caffeine during pregnancy are still unclear. 

Follow Sara G. Miller on Twitter @SaraGMiller. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Coffee drinkers may have more reasons to enjoy another cup, as a large new study suggests that people who drink up to five cups of regular or decaffeinated coffee daily may be slightly less likely to die early from any cause or certain chronic conditions.

Men and women in the study who drank moderate amounts of coffee — one to five 8-ounce cups a day — were found to have a lower risk of dying over a 30-year period from heart disease, type 2 diabetes, neurological diseases and suicide compared with the people in the study who didn't drink coffee, according to the findings, published today (Nov. 16) in the journal Circulation.

The research showed that people in the study who drank coffee moderately lived slightly longer, and had a reduced risk of death from some chronic diseases, compared with the people who didn't drink coffee, said Dr. Frank B. Hu, a professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health and a co-author of the study. Other research has established links between coffee drinking and a reduced risk of early mortality, but this new study was one of the largest to show these associations, he said.

The findings also suggest that regular, moderate consumption of coffee is not bad for people, and the study found no evidence that it can cause heart disease or cancer, Hu said. [10 Interesting Facts About Caffeine]

In the study, the researchers analyzed data collected from three ongoing long-term studies. They looked at about 75,000 women in the Nurses' Health Study, who were ages 30 to 55 when the study began; 93,000 women in the Nurses' Health Study 2, who were ages 25 to 42 at the study's start; and about 45,000 men enrolled in the Health Professionals Follow-up Study, who were ages 40 to 75 when the study began.

At the start of all three studies and every four years during them, participants reported how frequently they ate certain foods during the previous year, including their consumption of regular and decaf coffee.

Although moderate coffee consumption was linked with a slightly lower chance of dying during the study compared with not drinking any coffee, high coffee consumption — drinking more than five cups of regular or decaf a day — did not provide even more health benefits and had no influence on mortality rates, the researchers said.

Health perks

Moderate coffee drinking appears to be more healthful than harmful, Hu told Live Science. There are lots of components of coffee — such as antioxidants, the mineral magnesium and other chemical compounds — that may improve insulin sensitivity and reduce chronic inflammation in the body, he said.

It appears to be the other components in coffee, and not caffeine, that may be responsible for the beneficial effects associated with heart disease and diabetes, Hu said. Caffeine may be more likely to play a role in preventing death from neurological diseases and suicide, but this current study did not have enough data to show this effect, he said. Coffee may have an antidepressant effect, Hu noted.

Among all the good news about coffee, the study did find some bad news for coffee drinkers who smoke. When the researchers took into account whether coffee drinkers were smokers, they found that smoking masked the beneficial health effects seen with coffee drinking, Hu said.

For nonsmokers, moderate amounts of coffee seem to have beneficial effects on the risk of many chronic diseases, and this translates into a relatively modest influence on mortality, Hu said.

"The main thing is that moderate coffee drinking doesn't reduce longevity," he said.

Regular consumption of coffee can be included in a healthy diet, Hu said. Still, he doesn't recommend that people start drinking coffee as a preventive strategy to live longer or avoid certain illnesses. Some people are sensitive to caffeine's effects, and children and pregnant women should avoid too much caffeine, he said.

Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Having just one energy drink can cause short-term changes in healthy adults that, over time, could increase their risk of heart disease, a new study finds.

In the study, participants who drank one 16-ounce (480 milliliters) can of Rockstar energy drink had higher blood pressure and higher levels of the hormone norepinephrine, after they drank the energy drink than before they consumed it. Norepinephrine is released by the adrenal glands and raises blood pressure; it is a cousin of the hormone adrenaline.

One Rockstar energy drink contains 240 milligrams (0.008 ounces) of caffeine, along with other stimulants, including 2,000 mg (0.8 ounces) of taurine and extracts of guarana seed, ginseng root and milk thistle, according to the study. [5 Health Problems Linked to Energy Drinks]

To test the effects of the drink, the researchers recruited 25 healthy adults to participate in the study. On two separate days, the researchers measured the volunteers' blood pressure, heart rate and blood levels of caffeine, glucose and norepinephrine. The researchers then asked the participants to consume either the energy drink or a placebo. The placebo was similar in taste, texture and color to the energy drink, but did not contain caffeine or other stimulants. 

Thirty minutes after the participants finished each drink, the researchers repeated their measurements. The volunteers also underwent several tests that increased their physical and mental stress. During these stress tests, the researchers once again measured blood pressure and heart rate.

After consuming the energy drink, the participants' systolic blood pressure increased, on average, by 6.6 points (from 108.4 mm Hg to 115.0 mm Hg), compared with an average increase of 3.3 points (from 108.3 mm Hg to 111.6 mm Hg) after drinking the placebo.

Norepinephrine levels also increased following the consumption of the energy drink. They rose, on average, 100 picograms per milliliter (from 150 pg/mL to 250 pg/mL), compared with an average increase of 39 pg/mL (from 140 pg/mL to 179 pg/mL) after drinking the placebo.

The changes seen in the study "may predispose [people] to increased cardiovascular risk," the researchers wrote in their study.

This is not the first study to suggest energy drinks may have a negative effect on heart health. In a study from earlier this year, the same research group found that energy drinks can raise people's blood pressure to potentially unhealthy levels.

However, the researchers noted that additional, larger studies are needed to confirm the results of the new research. The current study's limitations include the small sample size of adults and the use of only one type of energy drink, the researchers wrote.

Live Science reached out to Rockstar Inc. for comment, but did not hear back by press time.

The study was published in the journal JAMA today (Nov. 8) and was also presented at the American Heart Association's Scientific Sessions meeting, held in Orlando, Florida.

Follow Sara G. Miller on Twitter @SaraGMiller. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Coffee lovers, rejoice. There's more evidence that your morning mug won't harm your heart, according to a new study from Sweden.

In the study, researchers found that drinking coffee was not associated with an increased risk of a condition called atrial fibrillation, which is a type of irregular heartbeat, in either men or women.

"This is largest prospective study to date on the association between coffee consumption and risk of atrial fibrillation. We find no evidence that high consumption of coffee increases the risk of atrial fibrillation," Susanna Larsson, an associate professor of epidemiology at the Karolinska Institute in Sweden and lead author on the study, said in a statement.

"This is important because it shows that people who like coffee can safely continue to consume it, at least in moderation, without the risk of developing this condition," Larsson said.

The study comes on the heels of an earlier study from this year, which suggested that coffee may lower the risk of heart attacks.

In the new study, the researchers looked at data from about 42,000 men and nearly 35,000 women who were participating in two long-running studies, the Cohort of Swedish Men and the Swedish Mammography Cohort. In 1997, all the participants filled out questionnaires that asked about their health and diet, including how many cups of coffee they drank daily or weekly. During the 12-year follow-up period, the researchers used the Swedish Hospital Discharge Register to determine which patients developed atrial fibrillation.

The researchers found no association between coffee consumption and an increased risk of atrial fibrillation, though they did observe a slight increase in risk when they limited the analysis to men. However, this increase was not statistically significant (meaning it could have been due to chance), the researchers wrote.

"Whether men may be more sensitive to a high coffee or caffeine intake warrants further study," the researchers wrote in their article, published today (Sept. 22) in the journal BioMed Central.

The researchers also did a meta-analysis, looking at six other studies on atrial fibrillation and coffee intake, which confirmed their results.

The researchers cautioned that although coffee does not appear to increase the risk of atrial fibrillation, it may increase risk for other types of irregular heartbeats.

Follow Sara Miller on Twitter @SaraGMiller. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Teens who drink energy drinks a lot are more likely to get head injuries than those who don't consume the highly caffeinated beverages, a new study from Canada suggests.

Researchers analyzed information from a survey of more than 10,000 middle and high school students ages 11 to 20 in Ontario in 2013. Students were asked about their energy drink consumption, as well as whether they had experienced a traumatic brain injury (TBI), meaning they had sustained a blow to the head that left them unconscious for at least 5 minutes, or resulted in an overnight hospital stay.

About 22 percent of students said they had experienced a traumatic brain injury (TBI) in their lifetimes, and 6 percent said they'd had a TBI in the last year. Most of these injuries occurred while the teens were playing sports.

There was a link between energy drink consumption and having experienced a TBI. In the researchers analysis, they compared teens' odds of having a TBI in the past year with their odds of not having one. They found that for teens who had consumed energy drinks in the past week, the increase in odds of having a TBI was five times greater than it was for teens who didn't consume energy drinks at all. 

In other words, teens who consumed the drinks were far more likely to have a TBI than those who did not.

The findings are concerning, because energy drinks might interfere with the body's ability to heal from a TBI, the researchers said.

"Energy drinks, such a Red Bull and Rockstar, contain high levels of caffeine and change the chemical state of the body, which can prevent people from getting back on track after a TBI," study co-author Dr. Michael Cusimano, a neurosurgeon at St. Michael's Hospital in Toronto, said in a statement. "Brain injuries among adolescents are particularly concerning because their brains are still developing."

It's also possible that consuming energy drinks might increase a person's chances of experiencing another TBI, the researchers said. [5 Health Problems Linked to Energy Drinks]

However, the study found only an association between energy drinks and TBI; the researchers said they don't know which happened first, and cannot prove that drinking energy drinks increases teens' risk for TBI.

It's possible that people who consume energy drinks also have other underlying factors that predispose them to experiencing a TBI, the researchers said. For example, these individuals could have a personality type that tends to take risks. Or, it could be that teens who have experienced a TBI start consuming energy drinks as a way to cope with the effects of their injuries, the researchers said.

The new findings may not be surprising, given that previous studies have found that young athletes often consume energy drinks, and athletes are also at risk of TBI, the researchers said. But the new study also found a link between energy drink consumption and TBIs that teens got in other ways, such as falling down or getting in a fight.

Future studies are needed to better understand the reason for the link between energy drink consumption and TBI, and to examine exactly why teens are drinking these beverages, the researchers said.

The study is published today (Sept. 16) in the journal PLOS ONE.

Follow Rachael Rettner @RachaelRettner. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Drinking a cup of coffee at night may mess up your sleep in more ways than one: Caffeine not only keeps you awake but also affects your body's internal clock, which tells you when it's time to sleep and wake up, a new study suggests.

The finding shows that caffeine "affects our physiology in a way that we hadn't really considered in the past," said Kenneth P. Wright Jr., a co-author of the study and director of the Sleep and Chronobiology Laboratory at the University of Colorado.

The research may have implications for night owls who want to get up earlier, and for people who experience jet lag after traveling between time zones, the researchers said.

In the study, five healthy people spent a night in a laboratory, where researchers monitored their levels of melatonin, a hormone that increases at night and is an indicator of the body's internal clock, also known as circadian rhythm.

Three hours before bedtime, participants took either a pill that contained about as much caffeine as two shots of espresso, or a placebo. (The experiment was repeated on another night so that participants who received the caffeine instead received the placebo the next time, and vice versa.)

The caffeine pill delayed the body's release of melatonin by about 40 minutes, the researchers found. In other words, caffeine affected the body's internal clock, so that the start of "biological night" was pushed later, the researchers wrote in their findings.

Researchers have long known that caffeine causes the release of chemicals in the brain that promote wakefulness and arousal, Wright said. But the new findings show that caffeine also affects the body in another way, by influencing circadian rhythms. [Turn Off to Tuck In: 5 Sleep Tips for Gadget Junkies]

"We think this is another reason why we may have some sleep disruption" when we have caffeine before bedtime, Wright told Live Science.

A 40-minute delay in the release of melatonin could have a relatively large effect on a person, Wright said. For comparison, when people are exposed to bright light before bedtime — which is known to have a strong influence on the circadian clock — their release of melatonin is delayed by about 85 minutes.

Previous studies have suggested that people who consider themselves "night owls" tend to consume more caffeine than those who are early risers. The new findings suggest that consuming caffeine in the evening may play a role in why some people are night owls, Wright said.

If a night owl wants to start getting up earlier, "removing caffeine in the evening and afternoon" may be one way to help, Wright said.

In addition, a dose of caffeine that's properly timed may be able to help people better adjust to jet lag when they travel from east to west (and thus need to push back their internal clock), Wright said. However, more studies are needed to examine this idea, because caffeine might also make jet lag worse, Wright said.

The study is published today (Sept. 16) in the journal Science Translational Medicine.

Follow Rachael Rettner @RachaelRettner. FollowLive Science @livescience, Facebook& Google+. Original article on Live Science.

Caffeine is in coffee, tea and other products people consume every day, so why is powdered caffeine dangerous?

On Tuesday (Sept. 1), the Food and Drug Administration announced that it had issued warning letters to five companies that sell powdered caffeine, saying that their products pose a "significant or unreasonable risk of illness or injury to consumers."

Powdered caffeine products are much more potent than caffeine-containing beverages like coffee, and they're dangerous because it is easy for people to consume a lethal amount of powdered caffeine, the FDA said.

Just 1 teaspoon of the caffeine powder contains about the same amount of caffeine as 28 cups of regular coffee, the FDA said. In fact, 2 teaspoons of powdered caffeine would kill most adults, according to the Centers for Science in the Public Interest.

"Powdered caffeine is very concentrated," said Henry Spiller, director of Central Ohio Poison Center at Nationwide Children's Hospital. Most people are so comfortable with the effects of caffeinated beverages like coffee and soda that they don't realize that the amount they ingest is just milligrams, Spiller said.

The amount of caffeine in a teaspoon can vary in different powdered caffeine products, the FDA noted. A teaspoon of some powdered products can have about 5 grams of caffeine; by comparison, a cup of coffee has about 65 to 100 milligrams of caffeine, Spiller said.

At that level, 1 teaspoon of the powder contains as much caffeine as 50 to 75 cups of coffee.

"This is enormous. This is an overdose," Spiller told Live Science. [7 Foods You Can Overdose On]

Another problem with the powdered products is that consumers usually don't have the tools to measure a safe dose. The recommended serving size of powdered caffeine is just 50 milligrams to 200 milligrams — or about one-sixteenth of a teaspoon.

To measure out 50 milligrams of powder using a quarter-teaspoon measuring spoon, a consumer needs to fill just 6 percent of the spoon, which "cannot be accurately measured," the FDA said.

"The difference between a safe amount and a toxic dose of caffeine in these pure powdered products is very small," the agency said.

What's more, the smallest packages of powdered caffeine sold by some of the companies contain 100 grams of product, which is 2,000 recommended servings. And some companies sell powdered caffeine in packages of 25 kilograms, which contain up to 500,000 recommended servings.

High doses of caffeine can cause serious side effects, including increased blood pressure, a rapid or dangerously erratic heartbeat, seizures and even death, the FDA said. Two young adults — an 18-year-old in Ohio and a 24-year-old in Georgia — died in 2014 from accidental overdoses of powdered caffeine.

Although it's possible to overdose on caffeine by drinking upward of 50 cups of coffee, most people would probably stop before this point because they would be experiencing uncomfortable effects, like nausea or vomiting and a rapid heart rate, Spiller said. The danger with powdered caffeine is that you take this dose of caffeine all at once, he said.

Follow Rachael Rettner @RachaelRettner. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

An infographic that breaks down what happens in your body after you drink one Coke has gone viral, but health experts say some information in the graphic is exaggerated.

In addition, while soda is certainly not a healthy food choice, drinking a sugar-sweetened beverage once in a while wouldn't necessarily make a person unhealthy, the experts said.

"If you're drinking one soda on occasion … that doesn't equate to it being necessarily unhealthy," said Heather Mangieri, a spokesperson for the Academy of Nutrition and Dietetics and owner of the nutrition consulting company Nutrition Checkup in Pittsburgh. "The overall diet quality is what's important."

The infographic, which appears on the blog the Renegade Pharmacist, details seven changes that happen to the body during the first hour after drinking a Coke, including the effects of ingesting 39 grams of sugar. The information for the graphic was taken from a 2010 article on the website blisstree.com

On the whole, the science presented in the infographic is fairly accurate, said Dana Hunnes, senior dietitian at the Ronald Reagan UCLA Medical Center.

However, some of the wording is exaggerated, Mangieri said. For example, the infographic says that in the first 20 minutes of drinking a soda, "your blood sugar spikes, causing an insulin burst. Your liver responds to this by turning any sugar it can get its hands on into fat."

But the effects of drinking this amount of sugar can vary depending on whether a person is active or inactive at the time, and whether they've eaten or not, Mangieri said. [How Much Sugar Is in That? (Infographic)]

"What happens after you consume a beverage like this relies heavily on whether the body is in need of energy, and what you do after consumption," Mangieri said. If you are active after drinking a soda, "the chances of some of these things happening are significantly less," she said.

Whenever you consume large amounts of sugar, your pancreas responds by secreting insulin, a hormone that helps sugar get into cells. The insulin will signal the liver, muscle and fat cells in the body to take up sugar from the blood, in order to lower blood-sugar levels.

But if you don't need energy when you drink the soda, the liver and muscles will store glucose in the form of glycogen. It's only once this storage is "full" that the body stores the glucose as fat, Mangieri said.

"Saying that [sugar] just automatically turns to fat is an over-exaggeration for sure," Mangieri said. "If you're well-fed, and the calories are all extra, your body doesn't need it, then yes, your body can store that as fat. But if your body can use those calories as energy, then you're not necessarily going to immediately story that as fat," she said.

In addition, the infographic says that after 45 minutes, "Your body ups your dopamine production, stimulating the pleasure centers of your brain. This is physically the same way heroin works." But Mangieri said that dopamine is also released in response to other rewards that are generally viewed more positively, such as listening to classical music or having sex.

The infographic also describes the negative effects of caffeine, but these are not unique to soda. "Any food/beverage with caffeine or other stimulant will dilate the pupils, raise blood pressure and increase the amount of glucose that is temporarily in the bloodstream," said Julie Kennel, a registered dietitian and clinical assistant professor at The Ohio State University. "This is the typical 'fight or flight' response."

What's more, a single can of Coca-Cola contains about 39 milligrams of caffeine, less than the 100 mg of caffeine in an 8-ounce cup of coffee.

The infographic says that phosphoric acid in soda promotes the loss, through urination, of nutrients, including calcium, which is important for teeth and bones. Mangieri said that there is a link between high soda intake and an increased risk of fractures, but this could be because people who drink a lot of soda may also drink less milk. Phosphoric acid is also found naturally in other foods, like meat and dairy products, she noted.

Still, there are many reasons to avoid drinking a lot of soda. These beverages have no nutritional value, don't do a good job of keeping you full, and can replace other healthy foods and beverages such as milk, Mangieri said. "There are a lot better ways to get your calories" than by consuming 39 grams of sugar in one beverage, she said.

Follow Rachael Rettner @RachaelRettner. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Energy drinks might give you some pep — but they might also be priming you for heart problems, a new study finds.

Researchers found that energy drinks can raise blood pressure to potentially unhealthy levels. The effect was far more prominent in young adults who did not consume caffeine regularly, according to the study, presented March 14 at an American College of Cardiology meeting in San Diego.

In this study, the research team — led by Dr. Anna Svatikova, a cardiovascular-diseases fellow at the Mayo Clinic in Rochester, Minnesota — gave a can of a commercially available energy drink to 25 healthy volunteers, whose ages ranged from 19 to 40. On a different day, the participants drank the same amount of a placebo drink. The researchers measured the participants' heart rate and blood pressure before and after the drinks.

The participants experienced a more marked rise in blood pressure after consuming the energy drink than after drinking the placebo, according to the findings. The participants' average systolic blood pressure (the top number in a blood pressure reading) increased by 3 percent more after they drank an energy drink, compared with after they drank the placebo drink. [5 Health Problems Linked to Energy Drinks]

The effect was most dramatic in people who did not typically consume more than a small cup of coffee or other caffeinated drink daily. In this so-called "caffeine-naive" group, the blood pressure increase was twice as high as the increase seen in the people who drank at least the equivalent of a cup of coffee on a daily basis, the researchers said in a statement.

Even a small increase in blood pressure can have deadly consequences, depending on your age and resting blood pressure, said Sachin Shah, an associate professor of pharmacy at the University of the Pacific in Stockton, California, who was not involved in the study.

"An acute, moderate increase in blood pressure is typically not a cause of worry in healthy subjects," said Shah, who has done research on the effects of energy drinks. However, in older people or those with hypertension, a moderate increase may be a cause for concern, he said.

At a population level, an increase of three or four points on a systolic blood pressure reading could mean a significant increase in deaths from stroke, he told Live Science.

Scientists do not know whether it is the caffeine, taurine or other ingredients found in energy drinks — or a combination of ingredients — that can adversely affect the heart.

In a separate study, presented last year at an American Heart Association meeting by Maj. Emily Fletcher of the David Grant Air Force Medical Center, healthy volunteers experienced a greater increase in blood pressure after they consumed an energy drink compared to after they drank a coffee drink that had an equal amount of caffeine. This result, Fletcher said, suggests that ingredients in the energy drink other than caffeine were conspiring to raise blood pressure.

According to the Mayo Clinic, consuming up to 400 milligrams of caffeine a day appears to be safe for most healthy adults. That's roughly the amount of caffeine in four cups of brewed coffee, 10 cans of cola or two "energy shot" drinks.

Previous studies have associated the consumption of energy drinks with poor memory and learning, anxiety, hallucinations, abnormal heart rhythm, substance abuse, and risk-taking behaviors. A study published in the journal Pediatrics in 2011 found that children, in particular, are at high risk of cardiac abnormalities from consuming energy drinks because of their smaller body size.

Follow Christopher Wanjek @wanjek for daily tweets on health and science with a humorous edge. Wanjek is the author of "Food at Work" and "Bad Medicine." His column, Bad Medicine, appears regularly on Live Science.

Drinking upward of four cups of coffee a day may lower the risk of developing multiple sclerosis (MS), a debilitating disease that affects the nervous system, researchers say.

The finding isn't without its caveats, and the scientists said they do not recommend that anyone at risk for developing MS go out and start guzzling coffee. 

However, the study of nearly 7,000 people in the United States and Sweden  does support observations previously made in mice, and it provides the most compelling evidence to date that caffeine offers protection against numerous neurological disorders. The researchers will present the findings in April at the annual meeting of the American Academy of Neurology.

In people with MS, the body's immune system inexplicably attacks the protective covering around nerve fibers, called myelin. The damage interrupts proper communication between the brain and the rest of the body, resulting in muscle weakness, poor coordination, blurred vision and pain, among other symptoms.

There is no cure for the disorder, and medications reduce symptoms only partially and temporarily. MS is more common in people living at very northern and southern latitudes, suggesting an association with sun exposure and vitamin D levels in certain ethnic groups, but the condition's cause remains unknown.

More than 400,000 Americans and 2.4 million people worldwide have MS, according to the National Multiple Sclerosis Society. Most people experience their first symptoms, often blurred or double vision, between ages 20 and 40.

In 2008, scientists led by Margaret Bynoe at Cornell University reported that mice that were bred to develop an MS-like disease failed to develop the condition when fed high amounts of caffeine. (The mice consumed the equivalent caffeine of four to six cups of coffee.) The researchers' study was published in the Proceedings of the National Academy of Sciences (PNAS).

The scientists hypothesized that caffeine blocked a chemical in the body called adenosine, which would otherwise enable immune cells to enter the central nervous system and destroy myelin. [10 Interesting Facts About Coffee]

In experiments, the mice that were fed caffeine "had reduced numbers of inflammatory immune cells in their central nervous system and, therefore, did not develop MS-like symptoms," said Linda Thompson of the Oklahoma Medical Research Foundation, a co-author on the 2008 PNAS report.

Thompson said a similar biological mechanism might occur in humans to protect against MS.

In the new study, researchers examined two datasets that each included healthy people and MS patients; one of the datasets came from Sweden, and the other came from the United States.

Analysis of both datasets revealed that the people who did not drink coffee had about a 1.5-times increased risk of developing MS compared with those who drank more than 30 ounces, or about four cups, daily.

The scientists could not discern, however, whether coffee helps reduce the severity of symptoms or postpones the relapse of symptoms in people who already have MS.

In MS patient forums, people have discussed the topic of coffee drinking for several years, with some patients reporting benefits, such as clearer thinking, while others report a worsening of their symptoms, such as poor sleep and jittery nerves.

"I think from the MS perspective, there are too few data to support changing coffee intake at this time," said Dr. Ellen Mowry, who led the new study and is an assistant professor of neurology at Johns Hopkins University School of Medicine in Baltimore. "Further research should be done to evaluate the role of coffee, including caffeine, in MS, as it may lead to identifying new targets for treatment."

One limitation of the study is that coffee habits were self-reported and retrospective, with participants asked to recall their coffee drinking patterns from as far back as 10 years, Mowry told Live Science. Yet the fact that the results of the Swedish and U.S. studies were so similar is particularly compelling, she added.

Coffee, most likely due to the caffeine it delivers, has been shown to reduce the risk and severity of other neurological disorders, such as Parkinson's and Alzheimer's diseases, as well as non-neurological conditions like heart disease, type 2 diabetes, liver disease and some cancers.

On the flip side, coffee can cause gastrointestinal problems and increase the intensity and frequency of migraines for many people. Unfiltered coffee can increase your levels of "bad" LDL cholesterol. And the science remains unclear on whether more than a daily cup of coffee increases the risk of miscarriage among pregnant women.

But more to the bottom line, ongoing studies at Harvard School of Public Health following more than 130,000 volunteers have found no increased risk of death from drinking as much as six cups, or 48 ounces, of coffee daily.

So depending on one's personal disposition, there may be far more reasons to increase your coffee drinking instead of kicking the habit.

Follow Christopher Wanjek @wanjek for daily tweets on health and science with a humorous edge. Wanjek is the author of "Food at Work" and "Bad Medicine." His column, Bad Medicine, appears regularly on Live Science.