Oral magnesium supplementation improves insulin sensitivity and metabolic control in type 2 diabetic subjects: a randomized double-blind controlled trial.

OBJECTIVE To determine whether oral magnesium supplementation (as magnesium chloride [MgCl(2)] solution) improves both insulin sensitivity and metabolic control in type 2 diabetic subjects with decreased serum magnesium levels. RESEARCH DESIGN AND METHODS This study was a clinical randomized double-blind placebo-controlled trial. A total of 63 subjects with type 2 diabetes and decreased serum magnesium (serum magnesium levels </=0.74 mmol/l) treated by glibenclamide received either 50 ml MgCl(2) solution (containing 50 g MgCl(2) per 1,000 ml solution) or placebo daily for 16 weeks. Chronic diarrhea, alcoholism, use of diuretic and/or calcium antagonist drugs, and reduced renal function were exclusion criteria. Homeostasis model assessment for insulin resistance (HOMA-IR) was used as the parameter of insulin sensitivity and glucose and HbA(1c) as parameters of metabolic control. RESULTS At the end of the study, subjects who received magnesium supplementation showed significant higher serum magnesium concentration (0.74 +/- 0.10 vs. 0.65 +/- 0.07 mmol/l, P = 0.02) and lower HOMA-IR index (3.8 +/- 1.1 vs. 5.0 +/- 1.3, P = 0.005), fasting glucose levels (8.0 +/- 2.4 vs. 10.3 +/- 2.1 mmol/l, P = 0.01), and HbA(1c) (8.0 +/- 2.4 vs. 10.1 +/- 3.3%, P = 0.04) than control subjects. CONCLUSIONS Oral supplementation with MgCl(2) solution restores serum magnesium levels, improving insulin sensitivity and metabolic control in type 2 diabetic patients with decreased serum magnesium levels.