The effect of lowering blood pressure by magnesium supplementation in diabetic hypertensive adults with low serum magnesium levels: a randomized, double-blind, placebo-controlled clinical trial

To test the blood pressure (BP)-lowering effect of oral magnesium supplementation ( that is, magnesium chloride (MgCl2) solution) in diabetic hypertensive adults with hypomagnesaemia not on diuretic treatment but receiving concurrent captopril, we conducted a double-blind, placebo-controlled trial. Eighty-two subjects between 40 and 75 years of age were randomly enrolled. Over 4 months, subjects in the intervention group received 2.5 g of MgCl2 (50 ml of a solution containing 50 g of MgCl2 per 1000 ml of solution) equivalent to 450 mg of elemental magnesium, and control subjects inert placebo. The primary trial end point was a reduction in systolic (SBP) and diastolic (DBP) blood pressure. Complete follow-up was achieved for 79 of the 82 randomized subjects. SBP (-20.4 +/- 15.9 versus -4.7 +/- 12.7 mmHg, P = 0.03) and DBP (-8.7 +/- 16.3 versus -1.2 +/- 12.6 mmHg, P = 0.02) showed significant decreases, and high-density lipoprotein-cholesterol (0.1 +/- 0.6 versus -0.1 +/- 0.7 mmol l(-1), P = 0.04) a significant increase in the magnesium group compared to the placebo group. The adjusted odds ratio between serum magnesium and BP was 2.8 (95% CI: 1.4-6.9). Oral magnesium supplementation with MgCl2 significantly reduces SBP and DBP in diabetic hypertensive adults with hypomagnesaemia.