Effects of Oral Magnesium Supplementation on Vascular Function: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

Introduction: The effects of magnesium (Mg) supplementation on vascular function have been evaluated in some randomized controlled trials (RCT) but their results are conflicting.

Aim: A systematic review and meta-analysis were conducted to summarize the effects of oral Mg supplementation on vascular function in RCT.

Methods: The databases MEDLINE (PubMed), Embase, Web of Science and Cochrane Library were accessed from inception to May 27, 2019. Intergroup differences (treatment vs. control group) related to changes in flow-mediated dilation (FMD) and pulse wave velocity (PWV), expressed as mean and standard deviation, were used to evaluate the effect of Mg supplementation on these outcomes. The results of the meta-analysis were expressed using a random-effects model. The heterogeneity between studies was evaluated using the I statistic.

Results: The oral supplementation of Mg had no significant effect on FMD (mean difference 2.13; 95% CI - 0.56, 4.82; p = 0.12) and PWV (mean difference - 0.54, 95% CI - 1.45, 0.36, p = 0.24). Heterogeneity for both outcomes (FMD and PWV) was high (I = 99%, p < 0.001). However, in subgroup analyses, oral Mg significantly improved FMD in studies longer than 6 months, in unhealthy subjects, in individuals older than 50 years, or in those with body mass index (BMI) ≥ 25 kg/m. The reduced number of RCT and the heterogeneity among them were the main limitations.

Conclusions: This meta-analysis suggest that oral Mg supplementation may improve endothelial function when conducted at least for 6 months and in unhealthy, overweight or older individuals. Registration number: PROSPERO CRD42019111462.