The analysis, to be published in the February issue of the American Journal of Clinical Nutrition, combined the results of seven studies published in the last 14 years in the United States, Europe and Asia. Researchers tracked how much magnesium people consumed and how many had a stroke over an 11 to 12 year period.
The average daily magnesium intake of study participants was less than the recommended intake. (In Canada and the U.S. men and women over age 30 need 420 and 320 milligrams of magnesium each day.)
For every extra 100 milligrams of magnesium people consumed each day above the average intake (roughly 200 milligrams), the risk of having any type of stroke fell by 8 percent.
A higher magnesium intake prevented ischemic stroke - the type caused by a blood clot - but did not significantly lower the risk of hemorrhagic stroke. Every 100 milligram increase of magnesium above the average was linked with a 9 percent reduced risk of ischemic stroke. In other words, people who consumed 400 milligrams of magnesium per day were 16 percent less likely to have a stroke.
Magnesium is thought to guard against stroke through its influence over risk factors for the disease. The mineral is needed to maintain healthy blood pressure. A 2006 review of 12 randomized trials showed that magnesium supplementation lowered elevated blood pressure.
Magnesium also helps regulate blood sugar (glucose) by influencing the release and activity of insulin, the hormone that clears sugar from the bloodstream. A 2010 study reported that among 4500 adults, those who consumed the most magnesium - 400 milligrams per 2000 calories - were 47 percent less likely to develop type 2 diabetes over the 20 year follow up compared to those whose diets provided only half as much.
Higher magnesium intakes have also been linked with lower levels of inflammation, a risk factor for diabetes and cardiovascular disease.
Some of the best food sources of magnesium include black beans, chickpeas, kidney beans, navy beans, soybeans, firm tofu, spinach, Swiss card, halibut, almonds, cashews, sunflower seeds, yogurt and wheat germ.
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