Vitamin D supplementation for improving sperm parameters in infertile men: A systematic review and meta-analysis of randomized clinical trials.

Objective: Vitamin D has been hypothesized to have a potential role in altering sperm motility and metabolism. However, experimental studies have demonstrated inconsistent results between vitamin D and sperm parameters. This study aims to investigate the role of vitamin D supplementation to improve sperm parameters in infertile men.

Methods: This is a systematic review and meta-analysis study. We comprehensively conducted a search on ClinicalTrials.gov, IRCT.ir, Europe PMC, and PubMed and collected published studies on vitamin D supplementation and sperm parameters for infertile men. The risk of bias was assessed by using Risk of Bias version 2 (RoB v2) and the statistical analysis was performed by using Review Manager 5.4 software.

Results: Five trials with a total of 648 infertile men were included. Our meta-analysis showed that supplementation with vitamin D may significantly improve total sperm motility [mean difference 4.96 (95% CI 0.38, 9.54), p = 0.03, I² = 69%], progressive sperm motility [mean difference 4.14 (95% CI 0.25, 8.02), p = 0.04, I² = 89%], and normal sperm morphology [mean difference 0.44 (95% CI 0.30, 0.57), p < 0.00001, I² = 0%] better than placebo in infertile men. However, total sperm count (p = 0.15), sperm concentration (p = 0.82), and semen volume (p = 0.83) did not differ significantly between two groups.

Conclusions: Vitamin D supplementation may improve sperm motility, progressive sperm motility, and morphology in infertile men. Vitamin D supplementation may be considered in managing male fertility issue.