Vitamin D in human reproduction: a narrative review

Abstract

Special attention has been given to the effect of vitamin D supplementation on fertility outcomes in both sexes. The purpose of this narrative review was to elucidate the role of vitamin D in male and female reproduction, providing current evidence from both animal and human studies. Using PubMed and Medline, we searched for publications during the last 30 years regarding the role of vitamin D in human reproduction. Accumulating evidence from animal and human studies suggests that vitamin D is involved in many functions of the reproductive system in both genders. In women, vitamin D status has been associated with in vitro fertilization (IVF) outcome, features of polycystic ovarian syndrome (PCOS) and endometriosis. Although several data converge towards a beneficial effect of vitamin D supplementation in metabolic disturbances in women with PCOS, a significant knowledge gap precludes the establishment of a clear cause-effect relationship. In men, vitamin D status has been associated with semen quality and sperm count, motility and morphology. There is evidence for a favourable effect of vitamin D supplementation on semen quality, testosterone concentrations and fertility outcomes. Studies with superior methodological characteristics are needed in order to establish a role for vitamin D on the treatment of female and male infertility. Recent data on vitamin D provide new insights in the complex pathogenesis and treatment of infertility.