Got Magnesium? Those With Heart Disease Should

Medically Reviewed by Gary D. Vogin, MD
From the WebMD Archives

Nov. 9, 2000 -- Every cell in the body needs magnesium. It helps keep muscles strong and nerves alert. And a new study in the journal Circulation suggests that daily magnesium supplements can even help an ailing heart.

Lead author C. Noel Bairey Merz, MD, tells WebMD that magnesium supplements enabled heart disease patients to exercise for longer periods and appeared to protect their hearts from the stress of exercise. Magnesium also restored some of the blood vessels' ability to open up when the body needs more blood. Merz is director of the preventive and rehabilitative cardiac center at Cedars-Sinai Medical Center in Los Angeles.

Half of the patients in the study took a supplement containing 365 mg of magnesium twice a day for six months. The other half took a placebo. Merz tells WebMD that at the end of the study, the patients who took magnesium had better blood vessel function and their hearts showed less stress during treadmill exercise compared to the placebo group. Nearly three-quarters of the patients were magnesium-deficient at the beginning of the study, but their levels rose to nearly normal by the end.

So what is it about magnesium that makes it such a friend to the body? It could be that magnesium helps the body's cells fend off stress. Magnesium-deficient cells also are more vulnerable to injury, and patients with heart disease may have greater need for magnesium, Merz says.

Carla A. Sueta, MD, PhD, who was not involved in the study, says, "we probably should move toward routine screening" for all patients with heart disease and offer supplements to all those found to be deficient. She cautions that the simple blood test available to doctors is not an accurate measure of magnesium levels. If the tests results are low, magnesium levels are probably very low in reality, so even someone with normal levels may still need supplements. Sueta is associate professor of medicine at the University of North Carolina at Chapel Hill, N.C.

Similar magnesium supplements are available over-the-counter in the U.S., but they might not provide similar benefits. "The product we used is from Germany, where supplements of this kind are regulated and quality is monitored," Merz says. "Because that is not the case in the U.S., it is impossible to know what you are getting in a supplement, or even whether it contains any magnesium at all. Patients who decide to try magnesium supplements available in the U.S. are probably fairly safe unless they have kidney problems," according to Merz.

However, he does suggest that people "follow the dietary recommendations to eat five to seven helpings of fruits or vegetables and two or three of nonfat dairy products every day. If everyone did that, we probably would not see the levels of magnesium deficiency we often find."

The most important food sources of magnesium are green vegetables like spinach, nuts, seeds, and some whole grains.

The research was funded in part by Asta Medica Co. Inc., manufacturer of the magnesium supplements used in the study.