From recommendations of drinking eight glasses of water a day to warnings about staying in from the cold when sick, some medical myths endure no matter how many times they've been disproved. Here are 10.
Myth: Vaccines can cause the flu (and autism).
While the body can react to any shot with a low-grade fever, rumors that a flu shot can cause the flu are "an outright lie," said Dr. Rachel Vreeman, co-author of Don't Swallow Your Gum! Myths, Half-Truths, and Outright Lies about Your Body and Health (St. Martin's Griffin, 2009).
The <a href="h1n1-virus-adapting-human-immunity-0458/">flu shot</a> does contain dead flu viruses but they are, well, dead. "A dead virus cannot be resurrected to cause the flu," Vreeman said.
As for vaccines causing autism, this myth was started in 1998 by an article in the journal The Lancet. In the study, the parents of eight (count 'em, eight) autistic children said they believed their children acquired autism after they received a measles, mumps and rubella vaccination. Correlation was quickly confused with causation, and since then, rumors have run rampant despite many studies such as a 2002 study in the New England Journal of Medicine of 530,000 (count 'em, 530,000) children that have found nothing to suggest that vaccinations increase the risk of becoming autistic.
Unfortunately, the endurance of this myth, said Vreeman, who also conducts pediatric research, continues to eat up time and funding dollars that could be used to make advances in autism, rather than proving, over and over again, that vaccinations do not cause the condition.
Myth: Supplements always make you healthier.
An increasing number of studies are finding that vitamin supplementation may not only be ineffectual but may even be dangerous. For example, people downing vitamins C and E may be predisposing themselves to cancer, according to a study published earlier this year in the journal Stem Cells, as high doses of these antioxidants can cause genetic abnormalities. Similarly, a study published this year in the journal Cancer Research linked fish oil supplements with cancer in mice.
"The FDA does not require supplements to be regulated in the same way that drugs are, which can be a real problem," Vreeman said. As a result, the safety of many <a href="experts-question-safety-of-dietary-supplements-0269/">supplements</a> has not been rigorously studied.
Furthermore, the bottles can sport unsubstantiated claims and even make errors in dosage recommendations, she said.
There is no need to worry about overdosing, however, if the good-for-you compound is coming from real food, rather than a pill. "A vitamin pill is not the answer," Vreeman said. "Eating more healthily in general is the answer."
Myth: Cold weather makes you sick.
"This myth is common around the world, but it is just not true," Vreeman told MyHealthNewsDaily. Studies have shown we may feel more cold symptoms real or imaginary when we are chilled (after all, a cold is called a cold for a reason), but the temperature does not make us more susceptible to viruses. This has been known since at least 1968, when a study in the New England Journal of Medicine showed what happened when researchers exposed chilly people to the rhinovirus (one cause of the common cold).
Whether shivering in a frigid room or stuttering in an icy bath, people were no more likely to get sick after sniffing cold germs than they were at more comfortable temperatures.
And if you are already sick, there is no reason you can't go out into cold weather. While rest is good for an ill body, chilly temperatures aren't going to make a difference on recovery time, Vreeman said. In fact, while the research is in its early stages, "it is possible that being exposed to cold may even help your body in some way," she said.
Some scientists speculate that colds are more common in cooler months because people stay indoors more, interacting more closely with one another and giving germs more opportunities to spread.
Myth: We use only 10 percent of our brains.
Motivational speakers and other self-help gurus have been promoting this one since as early as 1907, as a way to encourage people to tap into some latent capacity, explains Vreeman and co-author Aaron Carroll, both of Indiana University School of Medicine. But none of these people were basing the proclamation on sound science.
Today, we can take a look at any <a href="mri-holds-promise-of-better-autism-diagnoses-0818/">brain scan</a>, measuring activity at any given time, and have a big laugh at this myth. "You just don't see big dormant areas," Vreeman said.
So why does the idea still linger in popular culture?
"I think we like it," Vreeman said. "We want to think we haven't reached our full potential."
Myth: Sugar turns kids into little monsters.
It can be hard to find a parent that does not believe this, Vreeman said. "But it is in their heads."
In one particularly clever study among a slew of studies finding sugar's nil effect on <a href="caffeine-increases-teen-boys-blood-pressure-0841/">unruliness</a> kids were given Kool-Aid sweetened with aspartame, a compound that contains no sugar. Researchers told half of the parents the Kool-Aid contained sugar, and told the other half the truth. The parents who thought their kids were riding a sugar-high reported their children were uncontrollable and overactive. But a sensor on the kids' wrists, that measured activity level, said the opposite: The kids were actually acting subdued. The study was published in the Journal of Abnormal Child Psychology in 1994.
Sugar is often given at times when the rules are loosened and there are lots of other kids around like birthday parties and holidays, Carroll said. These factors may be behind the myth's persistence in popular culture, he said.
Myth: You need to stay awake if you've had a concussion.
Concussions are relatively common, and while they always merit medical attention, they are rarely severe or life- threatening.
Warnings to stay awake after a <a href="children-sports-concussions-increasing-100831-0276/">concussion</a> most likely grew out of a misunderstanding about a particular type of head injury one that involves brain bleeding where a "lucid period" is followed by a coma or worse. But this is very uncommon and doesn't pertain to people with normal concussions, Vreeman said.
"If you've been evaluated by a doctor, and he has said that you have a mild regular concussion, you don't need to worry that someone has to wake you up every hour," she said.
Myth: Chewing gum stays in your stomach for 7 years.
While it is true that many of the ingredients in gum, such as elastomers, resins and waxes, are indigestible, that does not mean they hang out in our guts for a subset of eternity.
Plenty of what we eat even things we are recommended to eat, such as fiber is indigestible. But the digestive system is a robust piece of organic machinery, and anything it can't absorb, it moves along.
Despite the stickiness and strange consistency of gum, "it passes right through your digestive tract and into the toilet," Vreeman explained.
Myth: Reading in the dark or sitting too close to the TV ruins your eyesight.
Dim light, or alternatively, staring into the multicolored tube at close range, can undoubtedly make your eyes work so hard they hurt. But there is no evidence that these practices cause long-term damage, Vreeman said.
The TV myth may have started in the 1960s, and at that time it may have been true. Some early color TV sets emitted high amounts of radiation that could have caused eye damage, but this problem has long been remedied, and today's TV and computer monitors are relatively safe, she said.
If you or your child tend to sit so close to the computer or TV it hurts the eyes, it may be time to check for nearsightedness. But sitting too close does not create a need for glasses even if getting glasses can remedy the habit.
Myth: You should drink at least 8 glasses of water a day.
"In general, we are not all walking around in a dehydrated state," Vreeman said, adding that our bodies are very good at regulating our fluid levels.
The eight-glasses-a-day myth likely started in 1945 when the Food and Nutrition Board of the National Research Council said adults should take in about 2.5 liters of water a day (equivalent to about eight glasses, or two-thirds of a gallon). While most media outlets reported just that, the council actually went on to explain that most of the 2.5 liters comes from food.
The recommendation should be amended to: Drink, or eat, about eight glasses of fluid a day.
Myth: You should wait an hour after eating before you go swimming.
This myth has ruined many summer afternoons, forcing young and old to swelter in the heat while cool waters beckoned all because they were careless enough to down a pb&j.
Let the ban be lifted: There is no special reason not to swim after eating, Vreeman said.
True, any type of vigorous exercise can be uncomfortable (although not dangerous) after an overwhelming feast. But for most of us whose waterfront dining experience includes sand-dusted chips and soggy sandwiches that is hardly a concern.
And cramps can happen anytime, whether you've eaten or not. If you are swimming in waters so rough that a charley horse will mean the death of you, you should probably swim elsewhere. Just don't forget the picnic!