May/June 2002 Alternative Health
Magnesium and Heart Health

by Jenny Thompson

In a study, published in the latest issue of the American Journal of Clinical Nutrition, researchers from the U.S. Department of Agriculture tracked the effects of a magnesium-deficient diet on 22 healthy postmenopausal women between the ages of 47 and 78. The women all ate the same meals for six months as they lived together under close supervision, taking in about 130 mg of dietary magnesium each day. But half the women also took in another 280 mg of magnesium in supplement form for the first 81 days while the other half took placebo; for the second half of the study period, the groups crossed over to the other treatment category.

The researchers assessed magnesium levels in urine and blood regularly throughout the study period. They also assessed heart-beat patterns through regular electrocardiograms. And here's what they found: not surprisingly, serum and urine concentrations of magnesium were substantially lower on the controlled diet. But they also discovered that heart rhythms were significantly affected by magnesium deficiency - specifically, a lack of magnesium made the heart beat more frequently than usual.

Scientists have long known that magnesium is a critical player in cell metabolism, helping to transport other minerals across cell membranes and affecting cell mechanisms that control the activity of muscle and nerve cells. But as the authors note, their research suggests "cardiac muscle seems to be more sensitive to [magnesium] intake than skeletal muscle."

This throws additional weight behind the developing theory that magnesium can help prevent many of the processes that lead to heart disease. In previous research, scientists found several important connections between magnesium deficiency and the development of heart disease; in fact, one study found that the risk of heart disease is higher in areas with "soft" water compared to those with "hard" water. (Hard water contains much more magnesium than soft.)

But there's more to magnesium intake than the water. You may also be at increased risk for magnesium deficiency if you regularly consume alcohol or diuretics, because both can increase urinary excretion of the mineral. Prescription medications, like the antibiotics Gentamicin, Amphotericin, and Cyclosporin, and the cancer drug Cisplatin, can increase magnesium excretion as well. Diabetics are also at increased risk of magnesium deficiency, as are those with Crohn's disease or other chronic gastrointestinal problems.

If you're concerned, ask your doctor to test your blood for magnesium levels. A normal range is anywhere between .66 and 1.23 mmol/L. Fortunately, it's easy to get more magnesium. The mineral is naturally present in green leafy vegetables, avocados, nuts and seeds, and whole grains, but usually in small amounts; you need to eat a wide variety of these foods regularly to get all you need. To make sure you're getting enough of this important mineral, you can also take magnesium supplements - they are readily available at health food stores and vitamin suppliers.

All of us could probably benefit from increasing our magnesium intake. But there is such a thing as too much. The tolerable upper intake level for supplemental magnesium is 350 mg per day for adults. That means that you shouldn't take any more than that in supplement form; more than that amount, in addition to the magnesium you get from food and water, could cause problems. At very high levels, the mineral can be toxic, causing kidney failure. But within reasonable limits, magnesium is an important part of a complete supplement program - and as this study shows, an important tool in your heart-health regimen.

Source: American Journal of Clinical Nutrition 2002;75:550-554

Jenny Thompson is the Director of the Health Sciences Institute. www.hsibaltimore.com