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.

Keywords:

• Zinc
• immune system
• adult
• systematic review
• meta-analysis

Acknowledgements

We want to thank S. Shahinfar and MR. Amini for their assistance.

Contributions of authors

AJ and ED designed the study. MA and AJ independently carried out the literature search and screening of articles; ED analyzed the data; AJ, ZN, and MA wrote the manuscript, and ED helped edit the writing. All authors read and approved the final manuscript.

Disclosure statement

The authors declare that they have no conflict of interest.

Funding source

This study has no funding.