Impact of Vitamin D₃ Supplementation on Androgens and Semen Parameters in Infertile Men: A Systematic Review and Meta-Analysis Based on Prospective Randomised Controlled Trials

This study aims to investigate the effects of vitamin D3 supplementation on androgen levels and semen parameters in infertile men. A comprehensive literature search was conducted across multiple databases, including PubMed, Web of Science, Cochrane Library, Scopus and Embase, to identify studies investigating the effects of vitamin D3 supplementation on androgen levels and semen parameters in infertile males. Data pertaining to changes in testosterone, sex hormone-binding globulin (SHBG), total sperm count and percentage of motile sperm before and after intervention were extracted and analysed. Six studies, involving 945 subjects, were included in the quantitative analysis. With regard to testosterone levels, vitamin D3 supplementation was found to increase testosterone, although this change was not statistically significant (standard mean difference (SMD) = 0.07, 95% confidence interval (CI): -0.11, 0.25). Similarly, an increase in SHBG levels was observed after vitamin D3 supplementation, but the change was not statistically significant (SMD = 0.42, 95% CI: -0.38, 1.22). By contrast, an increase in total sperm count was observed (SMD = 1.04, 95% CI: 0.11, 2.19). Additionally, vitamin D3 supplementation significantly increased the percentage of motile sperm (SMD = 0.82, 95% CI: 0.00, 1.64). In infertile men, vitamin D3 supplementation does not significantly affect androgen levels. Nevertheless, it may contribute to improvements in total sperm count and the percentage of motile sperm, potentially enhancing reproductive function.