Effect of magnesium supplementation on endothelial function: A systematic review and meta-analysis of randomized controlled trials

Background and aims: Findings of past studies are inconsistent regarding the effects of magnesium (Mg) supplementation on endothelial function (EF). We performed this meta-analysis to examine the effects of magnesium supplementation on flow-mediated dilation (FMD) and carotid intima media thickness (CIMT) as markers of EF.

Methods: Literature searches of English publications in MEDLINE and EMBASE databases were conducted up to November 2017. Results are reported as weighted mean difference (MD) with 95% confidence intervals (CI) using random effects model (DerSimonian-Laird method). Cochrane's Q test and I-squared (I²) were used to determine heterogeneity among included studies. To determine potential sources of heterogeneity, subgroup analysis was conducted for pre-defined criteria. Funnel plot and Egger's regression test were used to assess publication bias.

Results: Seven RCTs with 306 participants were included. Mg supplementation significantly increased FMD (MD: 2.97; 95% CI: 0.23 to 5.70%, p = 0.033). Between studies heterogeneity was high and subgroup analysis could not identify the sources of heterogeneity. Magnesium supplementation had no significant effect on CIMT (MD: -0.13 mm; 95% CI: 0.27, 0.01; p = 0.077) with high heterogeneity. Mg dose, duration of treatment, healthy status, baseline CIMT and sample size were the potential sources of heterogeneity. Mg supplementation could decrease CIMT to a greater extent in hemodialysis (HD) patients; lower doses of Mg, higher sample size and follow up duration and subjects with higher baseline CIMT also reduced the heterogeneity to some degree (p < 0.001).

Conclusions: Magnesium supplementation may improve endothelial function without affecting carotid intima media thickness.