Vitamin D and fertility

Vitamin D has broad and diverse biological functions. Many body tissues express the vitamin D receptor (VDR) which controls more than 200 genes responsible for processes such as metabolism, mineral homeostasis, bone resorption, cell cycle control and intestinal calcium transport.

Vitamin D also possesses an affinity for the reproductive system with VDR expression found in reproductive organs of males and females, and indeed, an increasing amount of evidence implicates deficiencies of vitamin D in hormone dysfunction.

Female infertility
Vitamin D stimulates a hormone (anti-mullerian hormone) which is associated with ovarian reserve preservation. High concentrations of vitamin D are also found in the membranes of the uterus during the first trimester of pregnancy, suggesting a role in implantation and embryo protection. Recent data also suggests that vitamin D enhances IVF outcomes by improving endometrial health.

Male infertility
Vitamin D deficiency is correlated with reduced sperm motility and morphology, and both deficiencies (< 50 nmol/L) and excesses (> 125 nmol/L) of vitamin D are associated with poor sperm count. Vitamin D is responsible for increasing intracellular calcium concentration and inducing a reaction (known as acrosome), essential during sperm and egg fusion during fertilisation.

Current research suggests that vitamin D plays an important role in conditions that affect fertility such as PCOS, uterine fibroids, improper semen parameters and the outcome of assisted reproductive techniques. Supplementation is advised in both individuals of a couple experiencing infertility where deficiency is observed. Dose is normally 1000–3000 IU per day depending on the deficiency.