Research appearing in Nutrition, Metabolism and Cardiovascular Diseases (April 7, 2009) looked at the effect magnesium supplementation had on blood pressure. The study was conducted to see if magnesium supplementation helped improve insulin sensitivity and blood pressure in 155 overweight adults. The subjects were randomly divided into two groups and received either 300 milligrams of magnesium per day or a placebo. The magnesium had no effect on insulin insensitivity, but it did have an effect on blood pressure. The subjects with hypertension who received magnesium supplementation had significant reduction in blood pressure at the end of 12 weeks. Systolic (the bigger number) blood pressure was reduced by an average of 5.6 points (mm of mercury) and diastolic (the smaller number) blood pressure was reduced by an average of 2 points. This effect was noticed only in patients with high blood pressure at the start of the study; the subjects with normal blood pressure did not experience a change in blood pressure.