Vitamin D and Infertility: The Evidence

Vitamin D is a lipid soluble vitamin synthesized by the skin upon exposure to UV light. Approximately 10–20% of vitamin D comes from dietary sources and 25OH-D is its circulating form. Vitamin D receptors are found in reproductive tissues including ovary, uterus, and endometrium permitting investigators to hypothesize a role for vitamin D in reproduction. Indeed, a number of animal studies provide evidence of vitamin D’s importance in fertility. Studies in humans, however, generally have not supported an effect of vitamin D on fertility outcomes. Several retrospective cohort studies did not demonstrate an association between vitamin D levels and pregnancy. Similarly, one study did not find correlation between anovulatory infertility and vitamin D intake. Very low levels of vitamin D, however, were associated with miscarriage in another study. A large meta-analysis of 11 studies and 2700 women did show an improvement in IVF success rates in those with higher levels of vitamin D. Finally, two small studies on vitamin D supplementation and pregnancy did not show a benefit of increasing vitamin D intake. In conclusion, the literature at best shows a minimal impact of vitamin D on infertility and IVF outcomes.