Investigation of the clinical efficacy of Zn supplementation in improvement of oxidative stress parameters: A systematic review and dose-response meta-analysis of controlled clinical trials.

Abstract

Clinical efficacy of zinc (Zn) supplementation in the improvement of oxidative stress biomarkers has been investigated in some clinical trial studies. The purpose of the current dose-response meta-analysis is to systematically aggregate and evaluate all related studies to highlight the possible effect of Zn supplementation on oxidative stress. Systematic search was performed on Scopus, PubMed/Medline, Web of Science and Embase up to 31 December 2020. The random effect method was used to perform pooled analysis. Possible sources of heterogeneity were found using subgroup analysis and meta-regression. In the presence of publication bias, trim and fill analysis was performed to adjust the results. Non-linear relationship between effect size and variables was investigated by performing dose-response analysis. The quality of included studies was assessed using Cochrane Collaboration's tool. Pooled-analysis of 18 studies showed that Zn supplementation improved MDA and Hcys levels (SMD=-1.53μmol/L; 95% CI: -2.22, -0.85; P<.001 and SMD=-0.62μmol/L; 95% CI: -1.08, -0.15; P<.001, respectively). There was no significant effect of Zn supplementation on TBARS (SMD=-0.59μmol/l; 95% CI: -1.31, 0.13; P=.108). Zn had maximum reducing effect on MDA in <40mg/day dosage. Zn supplementation reduces MDA and Hcys levels, but not TBARS level. Supplementation with Zn <40mg/day has an optimum effect on MDA level. Zn supplementation could be considered clinically as a beneficial approach in amending oxidative stress.