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What Are Magnesium Supplements?

A green bottle of magnesium pills spills out.
Studies show that magnesium may lower blood pressure, however, there are risks to taking the supplement.
Credit: Magnesium supplements photo via Shutterstock

Magnesium is the eighth most abundant element on the earth's crust, and is found in every organ in the human body. The physician Joseph Black first recognized magnesium as an element in 1755, but even before Black's time, physicians were recommending the magnesium carbonate "magnesia alba" for people with an upset stomach.

Today, researchers know magnesium plays a part in more than 300 reactions in the body. Magnesium is necessary to synthesize proteins, DNA and RNA. It plays a role in our metabolism, and cells use magnesium to transport calcium and potassium ions across the cell walls. Healthy magnesium levels are key to nerve function, muscle contraction, heartbeat, and healthy bones. Yet all of the magnesium in the average person weighs only 0.8 ounces (25 grams).

Magnesium is still used as an antacid and a laxative today. As a supplement, magnesium is touted to prevent hearing loss, kidney stones and migraine headaches. Magnesium supplements are also claimed to improve athletic performance, and treat sleep troubles including restless leg syndrome and insomnia. Low magnesium levels have been linked to osteoporosis, anxiety, irritability, depression and attention deficit hyperactivity disorder (ADHD).

Doctors sometimes recommend magnesium supplements to treat people with high blood pressure, preeclampsia, eclampsia, heart attacks, premenstrual syndrome (PMS) irregular heartbeat, or an unhealthy ratio of HDL (high-density lipoprotein) cholesterol to LDL (low-density lipoprotein) cholesterol.

Some people with certain chronic conditions — including diabetes, multiple sclerosis, fibromyalgia, and chronic fatigue syndrome — use magnesium supplements to control symptoms. Magnesium is occasionally recommended to ease altitude sickness, hay fever, Lyme disease, asthma and chronic obstructive pulmonary disease (COPD). Magnesium applied directly to the skin is said to treat skin infections and speed up wound healing. Magnesium has also been touted to ease muscle cramps, sensitivity to loud noises and kidney stones.

Many Americans do not get enough magnesium, according to the National Institutes of Health. But some groups of people, who have certain diseases or conditions are even more likely to have low magnesium levels. Heavy drinking and alcoholism can result in chronically low magnesium levels, and gastrointestinal conditions such as Crohn's disease and celiac disease can also deplete magnesium levels.

Older adults tend to have lower magnesium levels than young adults. This happens, in part, because the gut becomes less efficient at absorbing magnesium and the kidneys become less efficient at retaining magnesium with age. Type 2 diabetes can cause the kidneys to excrete too much magnesium, and in turn lead to a magnesium deficit. And some medications, such as diuretics, the heart drug digoxin and penicillamine (used for rheumatoid arthritis) can all interfere with magnesium in the body.

Do magnesium supplements work?

Supplements can increase magnesium levels, especially those in the forms of magnesium aspartate, citrate, lactate and chloride. A 2011 study in the American Journal of Clinical Nutrition showed people who take magnesium supplements typically get more than the recommended daily amount.

The recommended daily intake of magnesium ranges from 320 milligrams to 420 milligrams, depending on age or gender.

In fact, a healthy diet can easily provide enough magnesium. Whole grains, nuts, fish, meat, dark green vegetables, legumes and many fruits contain significant amounts of magnesium.

Inadequate magnesium levels are not likely to cause symptoms, but a full-blown magnesium deficiency can cause nausea, fatigue and weakness. Severe magnesium deficiency may cause numbness, tingling, muscle contractions, seizures, abnormal heart rhythm and personality changes. People with very low magnesium levels, or hypomagnesemia, may suffer from involuntary eye movements.

Magnesium deficiency can sometimes cause coronary spasm, a phenomenon in which the arteries that supply blood to the heart spasm and block blood flow. Dangerously low levels of magnesium can also result in low calcium (hypocalcemia), and low potassium (hypokalemia) — which can be fatal in extreme cases. Severely low magnesium can also result in a heart attack, respiratory arrest and death.

While magnesium supplements can certainly treat a magnesium deficiency, studies also show getting more magnesium than the bare minimum may help certain conditions. Several long-term studies have found a correlation between high magnesium levels and a lower risk of heart disease, sudden cardiac death and ischemic heart disease, according to the National Institutes of Health's Office of Dietary Supplements. Magnesium may also help prevent stroke. An analysis of seven studies including more than 200,000 people found that an extra 100 milligrams of magnesium a day reduced a person's risk of stroke by 8 percent, according to a February 2012 review in the American Journal of Clinical Nutrition.

Studies show magnesium supplements may lower blood pressure, but only by a little bit. One analysis of more than 22 studies on magnesium and blood pressure found that magnesium supplements reduced blood pressure by 2 to 4 mmHg, according to an April 2012 paper published in the European Journal of Clinical Nutrition. However, high blood pressure can fall within a range of 20 mmHg: from 140/90 mmHg to 160/100 mmHg. In the study, people's drop in blood pressure was greater when they increased their magnesium by eating more fruits and vegetables, or taking more than 370 milligrams of magnesium a day. Recommended daily intake of magnesium range from 320 milligrams to 420 milligrams, depending on age or gender. But because a diet with more fruits and vegetable will also increase levels of other nutrients, it is difficult to measure the independent effect magnesium has on blood pressure.

There is also a relationship between low magnesium levels and type 2 diabetes, studies have found, but exactly how the two are linked is still unclear. Low magnesium levels may worsen insulin resistance, which leads to uncontrolled blood sugar. But insulin resistance may also lead to low magnesium. Both situations may also be true where diabetes leads to low magnesium, and in turn low magnesium worsens diabetes, according to the NIH. A small number of studies show getting more magnesium may increase bone mineral density in elderly women, but more research is needed to clarify magnesium's potential in preventing or treating osteoporosis.

Guidelines from the American Headache Society and the American Academy of Neurology say magnesium is "probably effective" for migraine prevention. (However the guidelines recommend the nutritional supplement butterbur over magnesium to prevent migraines.)

The National Library of Medicine and the NIH determined that magnesium may help people with chronic fatigue syndrome and pain from fibromyalgia. Scientific evidence also indicates that magnesium may help PMS, high cholesterol, kidney stones, hearing loss, asthma attacks and chronic obstructive pulmonary disease (COPD). There are not enough studies to determine whether magnesium supplements could help anxiety, ADHD, hay fever, Lyme disease or multiple sclerosis, according to the NIH. Studies are less promising on magnesium's ability to boost athletic performance.

Are magnesium supplements safe?

Magnesium is one of the seven major minerals that the body needs in relatively large amounts (Calcium, potassium, sodium, chloride, potassium and phosphorus are the others). But too much of one major mineral can lead to a deficiency in another, and excessive magnesium can in turn cause a deficiency in calcium. Few people overdose on minerals from food. However, it is possible to get too much magnesium from supplements or laxatives.

People with kidney problems are more likely to experience an overdose of magnesium. Symptoms of toxic magnesium levels can range from upset stomach and diarrhea, to more serious symptoms of vomiting, confusion, slowed heart rate and dangerously low blood pressure. Severe magnesium overdoses can lead to problems breathing, coma, irregular heartbeat and even death.

Magnesium supplements can interact with several drugs. Taking magnesium too close to a dose of some antibiotics, including ciprofloxacin and moxifloxacin, may interfere with how the body absorbs the medicine. Similarly, magnesium can interfere with some osteoporosis drugs if the doses are taken too close together. Magnesium can also interfere with some thyroid medications. Magnesium can worsen side effects of some blood pressure medications, and increase the potency of some diabetes medicines. 

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