Effects of zinc supplementation on inflammatory biomarkers and oxidative stress in adults: A systematic review and meta-analysis of randomized controlled trials

Abstract

Background & Objective: Current evidence is debatable regarding the feasible effects of zinc supplementation on the inflammation and oxidative stress status of adults. This systematic review and meta-analysis aimed to clarify this inconclusiveness. Materials and Methods: Literature search was conducted via online databases such as PubMed, Scopus, ISI Web of Science, Cochrane Library, and Google Scholar until June 2020. The overall effect was presented as the weighted mean difference (WMD) at 95 confidence interval (CI) in a random-effects meta-analysis model. Publication bias was also assessed using Egger's and Begg's statistics. Results: In total, 25 clinical trials (n = 1428) were reviewed, which indicated that zinc supplementation significantly affects the concentration of C- reactive protein (WMD: -0.03 mg/l; 95 CI: -0.06, 0.0; P = 0.029), interlukin-6 (WMD: -3.81 pg/mL; 95 CI: -6.87, -0.76; P = 0.014), malondialdehyde (WMD: -0.78 mu mol/l; 95 CI: -1.14, -0.42; P < 0.001), and total antioxidant capacity (WMD: 95.96 mmol/l; 95 CI: 22.47, 169.44; P = 0.010). In addition, a significant between-study heterogeneity and a non-significant increment was reported in nitric oxide (WMD: 1.47 mu mol/l; 95 CI: -2.45, 5.40; P = 0.461) and glutathione (WMD: 34.84 mu mol/l; 95 CI: -5.12, 74.80; P = 0.087). Conclusion: According to the results, zinc supplementation may have beneficial anti-inflammatory and antioxidative effects in adults.