Vitamin D and Male Reproduction: Updated Evidence Based on Literature Review.

ABSTRACT

The purpose of this study was to clarify the vitamin D (VD) effect on male infertility. Our research was conducted using the following electronic databases MEDLINE, Embase, Web of Science, Scopus, ClinicalTrials.gov, and Cochrane Library. Selection criteria included all published randomized controlled trials and non-randomized studies, focusing on vitamin D and male reproductive function. The results showed that the effects of VD on male reproduction has been investigated in three different topics the molecular mechanism underlying VD effects on semen quality (SQ), the relationship between VD levels and SQ, and the effect of VD supplementation on SQ. Results supported the hypothesis of a relevant interrelation between concentrations of male VD and semen parameters, with particular reference to sperm motility; on the contrary, evidence on the effect of VD on male sex steroid hormone levels was inconclusive. The results of this review hold up the thesis that VD plays a role in male reproduction. Most of the data highlighted a positive effect on semen quality, particularly in sperm motility, both in fertile and infertile men. Additional dedicated studies are required to elucidate the still controversial aspects of this topic.