Vitamin D supplementation does not affect serum leptin and adiponectin levels in adults: A systematic review and meta-analysis of randomised controlled trials

Abstract

Background & aims: It is proposed that vitamin D supplementation might influence serum adipokines level; however, the recent meta-analyses have led to inconsistent results while they had methodological limitations. Therefore, this study aimed to examine the effects of vitamin D supplementation on serum adipokines through a systematic review and a meta-analysis of randomized placebo-controlled trials (RCTs) using a more comprehensive search strategy.
 Methods: PubMed, Google Scholar, and Scopus were searched to identify related articles published up to November 2017. Mean±standard deviation (SD) of changes in serum adiponectin and leptin were extracted, and the effect sizes were pooled using a random-effects model. Studies with Controlled clinical trials design were eligible. Two reviewers extracted mean values and SDs of the baseline, final and net change values of leptin and adiponectin in the intervention and control groups.
 Results: The pooled results indicated that vitamin D supplementation affects neither circulating leptin (Hedges’ g = 0.042, 95% CI: -0.294 to 0.378, p = 0. 0.807, n=15) nor adiponectin (Hedges’ g = -0.034, 95% CI: -0.243 to 0.174, p = 0.748, n=18) levels. Subgroup analysis showed that vitamin D supplementation might significantly decrease serum leptin level in patients with end stage renal disease (Hedges’ g = -0.634, 95 % CI: -1.221 to -0.047, p = 0.034).
 Conclusions: Although the current evidence does not support the significant effect of vitamin D supplementation on adiponectin and leptin levels, further research is required to reach more definitive conclusions.