Effects of oral magnesium supplementation on glycaemic control in Type 2 diabetes: a meta‐analysis of randomized double‐blind controlled trials

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Abstract
Aims  The aim of this study was to assess the evidence on the effect of oral magnesium supplementation on glycaemic control in patients with Type 2 diabetes.Methods  We searched the electronic databases of medline, embase and the Cochrane Controlled Trials Register up to January 2005. We identified nine randomized double‐blind controlled trials with a total of 370 patients with Type 2 diabetes and of duration 4–16 weeks. The median dose of oral magnesium supplementation was 15 mmol/day (360 mg/day) in the treatment groups. The primary outcome was glycaemic control, as measured by glycated haemoglobin (HbA1c) or fasting blood glucose levels; the secondary outcomes included body mass index, blood pressure (BP) and lipids. Using a random‐effects model, we calculated the weighted mean differences (WMD) and 95% confidence interval (CI).Results  After a median duration of 12 weeks, the weighted mean post‐intervention fasting glucose was significantly lower in the treatment groups compared with the placebo groups [−0.56 mmol/l (95% CI, −1.10 to −0.01); P for heterogeneity = 0.02]. The difference in post‐intervention HbA1c between magnesium supplementation groups and control groups was not significant [−0.31% (95% CI, −0.81 to 0.19); P for heterogeneity = 0.10]. Neither systolic nor diastolic BP was significantly changed. Magnesium supplementation increased on high‐density lipoprotein (HDL) cholesterol levels [0.08 mmol/l (95% CI, 0.03 to 0.14); P for heterogeneity = 0.36] but had no effect on total cholesterol, low‐density lipoprotein (LDL) cholesterol and triglyceride.Conclusions  Oral magnesium supplementation for 4–16 weeks may be effective in reducing plasma fasting glucose levels and raising HDL cholesterol in patients with Type 2 diabetes, although the long‐term benefits and safety of magnesium treatment on glycaemic control remain to be determined.