Zinc supplementation and immune factors in adults: a systematic review and meta-analysis of randomized clinical trials.

ABSTRACT

PURPOSE: This systematic review and meta-analysis aimed to investigate the effect of zinc supplementation on immune factors in randomized controlled trials. METHODS: A comprehensive search was done in PubMed, Scopus, Web of Science, Embase, and Cochrane databases up to December 2020. We used standard and weighted mean differences and 95% confidence intervals for net changes in selected parameters of immune responses. Subgroup analysis was used to find heterogeneity. RESULT: Overall, 35 RCTs comprising 1995 participants were eligible for this meta-analysis. There was a significant reduction of circulating CRP (WMD -32.4; 95% CI -44.45 to -19.62, p < 0.001), hs-CRP (WMD -0.95; 95% CI -1.01 to -0.89, p < 0.001), Neutrophil levels (SMD -0.46; 95% CI -0.90 to -0.01, p = 0.043), following zinc supplementation. CD4 level also increased significantly, (WMD 1.79; 95% CI 0.57 to 3, p = 0.004). Zinc supplementation had no significant effect on WBC (SMD -0.66; 95% CI -1.67 to 0.36, p = 0.204), lymphocyte (WMD 1.86; 95% CI -0.86 to 4.58, p = 0.181), monocyte levels (SMD -0.16; 95% CI -0.07 to 0.39, p = 0.167), CD3 (SMD 0.37; 95% CI -0.49 to 1.22, p = 0.399). CONCLUSION: Zinc supplementation decreased the CRP, hs-CRP and TNF-α, IL-6, neutrophil and increased CD3 and CD4 level significantly.