THE EFFECT OF ZINC SUPPLEMENTATION ON SERUM LEPTIN LEVELS: A SYSTEMATIC REVIEW AND META-ANALYSIS OF RANDOMIZED CONTROLLED TRIALS

Background and Aim: Prior studies have demonstrated that zinc potentially affects serum leptin levels. However, clinical trials done in this regard are not consistent. Therefore, in this meta-analysis we aimed to ascertain the actual effect of zinc supplementation on serum leptin levels in adults. Methods: Databases of PubMed, SCOPUS, and Google Scholar were methodically searched to identify relevant articles up to January 2018. Clinical trials that examined the effect of zinc supplementation on serum leptin concentrations as outcome variables in human adults were included. The mean difference (SD) of leptin changes in the intervention and placebo groups were used to calculate the overall effect size. Results: Totally, 663 articles were identified, of which 6 were eligible randomized controlled trials (RCTs) with 7 treatment arms. The analysis suggested that zinc supplementation exerts no significant effect on overall serum leptin (WMD: 0.74 ng/ml; 95% CI: -1.39 to 2.87, P= 0.49). Nevertheless, sex and duration of intervention seemed to impact the extent of zinc’s influence. In trials with female subjects, zinc consumption led to a significant decrease in serum leptin level (WMD: -1.93 ng/ml; 95% CI: -3.72 to -0.14, P= 0.03) as well as trials that lasted for more than 6 weeks (WMD-1.71 ng/ml; 95% CI: -3.07 to -0.35, P= 0.01), in comparison to the control group. Conclusion: Zinc supplementation did not significantly improve leptin concentrations, but it may result in a decreased circulating leptin level in studies with a duration of more than 6 weeks especially among females.

Keywords:

Zinc , Supplementation , Leptin , Meta-analysis