Magnesium in stroke prevention

STOCKHOLM, SWEDEN. Magnesium is of key importance to human health. It participates in over 300 enzymatic reactions in the body. A deficiency has been linked to conditions such as irregular heartbeat, asthma, emphysema, cardiovascular disease, high blood pressure, mitral valve prolapse, stroke and heart attack, diabetes, fibromyalgia, glaucoma, migraine, kidney stones, osteoporosis, and probably many more. Magnesium is particularly important when it comes to ensuring the health of the heart and bones. About 99% of the body's magnesium stores are found in the bones and tissues and heart tissue is particularly rich in this important mineral. Only 1% of the body's magnesium is actually present in the blood so a standard blood analysis is a very poor way of determining overall magnesium status.

The RDA (Recommended Dietary Allowance) is 420 mg/day for men and 320 mg/day for women. Unfortunately, recent surveys have shown that many Americans have a dietary intake of 200 mg/day or less. A study found that 74% of a cohort of 2000 elderly men and women did not consume the recommended amount. This same study also concluded that a high magnesium intake is associated with a significantly higher bone density in older white men and women. Every 100 mg/day extra intake of magnesium was found to correspond to a 2% increase in whole-body bone mass. Almonds, nuts, blackstrap molasses, wheat bran and wheat germ are good sources of magnesium; however, many people will, no doubt, prefer to take a magnesium supplement as an easy and reliable way of assuring an adequate daily intake. Up to 800 mg/day of elemental magnesium is probably safe; however, people with kidney disease or severe heart disease should not supplement with magnesium without their doctor’s approval.

A group of nutritional researchers at the Karolinska Institute now report that higher magnesium intakes are associated with a significantly reduced risk of suffering an ischemic stroke. Their meta-analysis covered 7 prospective studies involving 241,378 participants and 6,477 cases of stroke, about 5100 of which were ischemic (caused by a blockage in an artery). The remaining strokes were hemorrhagic (caused by rupture of an artery), or of unknown origin. All studies compared stroke risk with at least 3 different levels of magnesium intake ranging from less than 186 mg/day to 575 mg/day and included adjustments for potential confounders such as age, sex, smoking, hypertension and diabetes; most also corrected for body mass index, physical activity and alcohol consumption. The conclusion of the meta-analysis was that the risk of ischemic stroke decreases by 9% for each 100 mg/day of additional magnesium intake. Thus, if a person with a daily intake of 200 mg (typical intake in North America) were to increase their intake by 400 mg/day they would decrease their risk of suffering an ischemic stroke by 36%.

In an accompanying editorial, Drs. Song and Liu of Harvard Medical School point out that researchers have been studying the role of magnesium in cardiovascular health for nearly 80 years, ever since Zwillinger in 1935 reported that intravenous injection of magnesium sulfate suppressed digitalis-induced cardiac arrhythmia in humans. They suggest that the time has come to perform a large, double-blind and placebo-controlled randomized trial of magnesium for the primary prevention of cardiovascular disease. They conclude with the comment “Without a large trial that directly defines cardiovascular disease as a primary outcome, it is safe to predict that another 8 decades will go by while generations of nutritional scientists continue to debate magnesium’s efficacy for the primary prevention of cardiovascular disease.”
Larsson, SC, et al. Dietary magnesium intake and risk of stroke: a meta-analysis of prospective studies. American Journal of Clinical Nutrition, Vol. 95, 2012, pp. 362-66
Song, Y and Liu, S. Magnesium for cardiovascular health: time for intervention. American Journal of Clinical Nutrition, Vol. 95, 2012, pp. 269-70

Editor’s comment: Many afibbers are already supplementing with 400 to 600 mg/day of elemental magnesium thus potentially reducing their risk of ischemic stroke by 36 to 54%. This is clearly highly significant and using magnesium supplementation to achieve it avoids the many adverse effects of aspirin and warfarin, and would have the added benefit of potentially preventing or reversing osteoporosis by increasing whole-body bone mass by about 8%.