The fourth most abundant mineral in your body, magnesium is essential for hundreds of enzyme reactions that affect everything from bones and blood sugar to nerves and brain cells. Yet most Americans don't think about magnesium and routinely skimp on the foods that are the best sources of it. "Magnesium is essential for normal brain function," says neurologist Larry B. Goldstein, MD, FAAN, chairman of the neurology department at the University of Kentucky (UK) in Lexington. And eating a balanced diet is the ideal way to get what you need, he says. Magnesium may also help ease migraine and lower blood pressure.

Migraine

Low levels of magnesium in the bloodstream—due to stress, diet, genetics, or other medical problems—may contribute to inflammation, which could result in chronic migraine headaches. Low magnesium may also spread pain signals by allowing calcium to dock on certain receptors in the brain. A 2016 study in International Clinical Psychopharmacology showed that low serum concentration of magnesium was an independent risk factor in migraine attacks.

"People with migraine have lower levels of magnesium in the brain compared to migraine-free people," says Alexander Mauskop, MD, FAAN, director of the New York Headache Center and professor of neurology at SUNY Downstate Medical Center. "Up to 50 percent are deficient at the time of an attack. Some people may have inherited absorption problems or have irritable bowel syndrome. Alcohol also can reduce magnesium levels, which may explain why it can be a migraine trigger."

What the research says

Several small, older studies suggest that magnesium supplements reduce the number and pain of migraines. More recent studies, including a 2015 review in Cephalalgia and a 2018 review in the journal Headache, found limited evidence and concluded that getting magnesium from food was sufficient.

Should you try it?

"Extra magnesium won't help with migraine if your levels are in the normal range," says Dr. Mauskop. If you have a poor diet, increasing your consumption of healthy foods that contain magnesium may help, he adds, but may not be enough if you have migraines. "Ask your doctor about tests for magnesium deficiency," he suggests.

For people with chronic migraines and low magnesium levels, Dr. Mauskop recommends 400 milligrams of supplemental magnesium daily (in one dose or split into two doses, taken morning and evening). "It helps about one-quarter of the people who try it," he says, adding that if the supplement works, you probably have a magnesium deficiency.

Magnesium supplements are safe for most people; the most common side effect of taking too much is diarrhea. "Don't take magnesium if you have kidney disease," cautions Dr. Mauskop.

High Blood Pressure

Overall, people with the highest magnesium intake have a 10 percent lower risk for stroke than those who consume the least in observational studies, says Dr. Goldstein, who is also interim director of the UK-Norton Stroke Care Network. These studies don't prove cause and effect, but some researchers speculate that magnesium might offer some stroke protection by helping to control blood pressure and blood sugar and by discouraging the formation of blood clots, he says.

What the research says

A 2016 Chinese meta-analysis of 34 magnesium/blood pressure studies, published in Hypertension, showed that taking a 368 mg magnesium supplement daily for three months lowers systolic blood pressure by two points and diastolic pressure by 1.7 points.

But magnesium doesn't work alone, says Edgar R. (Pete) Miller III, MD, PhD, professor of medicine and epidemiology at Johns Hopkins University. "It may contribute by relaxing coronary blood vessels. But it works best in a diet that is also rich in calcium and potassium and low in sodium. This combination can lower systolic blood pressure by about 11 mm Hg—as good as a pill." Dr. Miller was one of the principal researchers of the Dietary Approaches to Stop Hypertension (DASH) diet studies.

Should you try it?

"It's better not to rely on any supplement to fix unhealthy food choices," Dr. Miller says. "Switching to a DASH diet and getting away from high-sodium, low-nutrient processed food may itself be an important part of controlling blood pressure and lowering your risk for stroke." Dr. Goldstein agrees. "Following a DASH or Mediterranean-type diet is optimal," he says. Exercise, weight control, not smoking, moderate alcohol consumption, and getting treatment for conditions like high blood pressure, diabetes, and atrial fibrillation are also key, he adds.

How to Get the Magnesium You Need

The Academy of Nutrition & Dietetics and the US Department of Agriculture both recommend getting magnesium from food before relying on supplements. Magnesium-rich foods also deliver fiber and other important nutrients. And supplements can interact with other medications you may be taking, such as bone-protecting bisphosphonates as well as tetracyclines and quinolone antibiotics.

Magnesium deficiency is rare in healthy adults because the kidneys can control the amount excreted from the body. But people with conditions that affect magnesium absorption—such as type 2 diabetes, alcohol dependence, Crohn's disease, and celiac disease—are at higher risk. Your magnesium stores may also be depleted by long-term use of drugs such as prescription and over-the-counter proton pump inhibitors, loop diuretics (like furosemide or Lasix), bumetanide (Bumex), thiazide diuretics (such as hydro-chlorothiazide/aquazide H), and ethacrynic acid (Edecrin). Signs of a magnesium deficiency can include sleep problems, constipation, headaches, fatigue, weakness, muscle cramps, and anxiety. With a more severe deficiency, people may experience numbness, tingling, seizures, and personality changes. A simple blood test can reveal a deficiency, and your doctor can suggest the appropriate supplement dose.

To get more magnesium:

• Choose whole grains. Switch from refined grains to whole grains. For example, a half-cup of brown rice has 38 mg, versus 10 mg for white rice.
• Eat leafy greens. A cup of cooked kale has 23.4 mg of magnesium, while the same amount of savoy cabbage has almost 41 mg and spinach has 157 mg.
• Add some beans. Legumes like red beans and black beans are good magnesium sources, as are soy, edamame, soy milk, and tofu.
• Go (a little) nuts. Snacking on an ounce of nuts provides 50 mg (for peanuts) to 80 mg (for almonds).
• Count your coffee. While a cup of regular coffee has only 7.2 mg of magnesium, there's 48 mg in a shot of espresso (caffeinated or decaf) and 82 mg in a 12-ounce latte.
• Avoid ultra-processed foods. People who consumed the most sugar-sweetened drinks, processed meats, salty snacks, heat-and-eat entrees, french fries, and sweets had an average daily magnesium intake 56 mg lower than those who had the fewest of these ultra-processed foods, according to a 2017 study in the journal Population Health Metrics.

Know Your Magnesium Numbers

The recommended daily allowance (RDA)—the amount that meets most healthy people's day-to-day needs—of magnesium varies by age and gender.

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