Effect of zinc supplementation on blood sugar control in the overweight and obese population: A systematic review and meta-analysis of randomized controlled trials

Abstract

BackgroundAlthough overweight and obese people have a higher risk of type 2 diabetes incidence than normal-weight individuals, the efficacy of zinc supplementation in blood sugar control in overweight and obese people remained unknown. This meta-analysis attempted to address this issue. MethodsDatabases including PubMed, Embase, and the Cochrane Library were searched from inception until May 2022 to identify randomized controlled trials (RCTs) investigating the effects of zinc supplementation among participants who were overweight or obese without language restriction. It is a random-effect meta-analysis that analyzed the impact of zinc supplementation on fasting glucose (FG) (i.e., primary outcome) and other variables including fasting insulin (FI), homeostasis model assessment-insulin resistance index (HOMA-IR), glycated hemoglobin (HbA1c), high-sensitivity C-reactive protein (hs-CRP), and 2-hour postprandial glucose (2 h- PG). ResultsAnalysis of 12 eligible RCTs involving 651 overweight/obese participants demonstrated that zinc supplementation significantly improves FG (weighted mean difference [WMD]: −8.57 mg/dL; 95% confidence interval [CI]: −14.04 to −3.09 mg/dL, p = 0.002), HOMA-IR (WMD: −0.54; 95% CI: −0.78 to −0.30, p < 0.001), HbA1c (WMD: −0.25%; 95% CI: −0.43% to −0.07%, p = 0.006), and 2 h-PG (WMD: −18.42 mg/dL; 95% CI: −25.04 to −11.79 mg/dL, p < 0.001) compared to those in the control group. After conducting subgroup analyses, we found that the primary outcome, FG, showed more significant results in the subgroups with Asia, Zinc supplementation alone, higher dose (≥30 mg) and patients with diabetes. ConclusionOur meta-analysis indicated that zinc supplementation benefits blood sugar control in overweight and obese populations, with an especially significant reduction in FG.