By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

Magnesium is a mineral that is important for many bodily functions. In animals deficiency of magnesium raises blood pressure, and giving supplements can lower it. Some epidemiological studies in humans have suggested that those who eat more magnesium in their diets may have lower blood pressures, but this has been difficult to establish with certainty.

A Japanese study has found that giving people magnesium pills does lower blood pressure. Sixty people with mild hypertension were given pills containing 400 milligrams of magnesium oxide twice a day (equivalent to 480 milligrams a day of magnesium) for eight weeks. Blood pressure was measured in the doctor's office, at home, and with 24-hour monitoring. All three methods showed a small but significant fall of blood pressure as a result of taking the magnesium, of about 2 mm Hg in men. The changes were greater in men with higher pressures at the start of the study. Magnesium did not lower the blood pressure in women.

Doctor's comments

The recommended daily intake of magnesium is 350 milligrams for men and 280 for women. Most people get less than this (estimates for the average intakes of American men and women are 280 and 215 milligrams). This study showed a modest reduction of blood pressure, which was most pronounced in men with higher pressures. Earlier studies have given inconsistent results, and the strength of this study is that all three methods of measuring blood pressure gave the same answer. The subjects in this study were eating less than the recommended amounts of magnesium before they went on the supplement

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