Effects of Magnesium Supplementation on Blood Pressure: A Meta-Analysis of Randomized Double-Blind Placebo-Controlled Trials.
Level 1 - systematic review of randomized trials
Meta-analysis of randomized double-blind placebo-controlled trials
PubMed 27402922 · doi:10.1161/HYPERTENSIONAHA.116.07664
What was done
Authors conducted a systematic review and random-effects meta-analysis of randomized, double-blind, placebo-controlled trials from MEDLINE and EMBASE up to February 2016. They evaluated oral magnesium supplementation in normotensive and hypertensive adults across 34 trials involving 2028 participants. Primary endpoints were weighted mean differences in systolic blood pressure, diastolic blood pressure, and serum magnesium concentrations. Dose-response relationships were evaluated using restricted cubic spline curves.
What was found
Magnesium supplementation at a median dose of 368 mg/d for a median duration of 3 months significantly reduced systolic blood pressure by 2.00 mm Hg (95% CI, 0.43 to 3.58) and diastolic blood pressure by 1.78 mm Hg (95% CI, 0.73 to 2.82) compared to placebo. Serum magnesium significantly increased by 0.05 mmol/L (95% CI, 0.03 to 0.07). A dose of 300 mg/d or a duration of 1 month was found sufficient to raise serum magnesium and lower blood pressure. Serum magnesium was negatively associated with diastolic blood pressure (P < 0.05) but not systolic blood pressure. Trials with high quality or low dropout rates showed greater blood pressure reductions (interaction P < 0.05).
Why it matters
This review provides evidence for a modest causal blood-pressure-lowering effect of oral magnesium supplementation in adults alongside measurable increases in serum magnesium concentrations.
Limits
The effect size is clinically small (roughly 2 mm Hg). The analysis pooled normotensive and hypertensive cohorts with heterogeneous baseline characteristics, and residual heterogeneity remained present despite stratified analyses. Long-term cardiovascular outcomes were not evaluated.
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