In the last decade,
vitamin D was in the spotlight in many fields of research. Despite numerous publications, its influence on reproductive health remains ambiguous. This paper presents an up-to-date review of current knowledge concerning the role of
cholecalciferol in human reproduction. It covers various
infertility issues, such as
polycystic ovary syndrome,
endometriosis,
myoma-induced
infertility, male infertility, premature ovary failure and in vitro fertilization techniques.
Vitamin D deficiency, defined as serum concentration of
25-hydroxycalciferol of less than 50 nmol/L, is commonly noted more frequently than only in fertility clinic patients. It is a global trend that is observed in all age groups. The results of original publications dated up to 2015 have been summarized and discussed in a critical manner. Most experts agree that
vitamin D supplementation is a necessity, particularly in women suffering from
obesity,
insulin resistance or small ovarian reserve, as well as in men with oligo- and
asthenozoospermia if serum concentration should fall below 50 nmol/L (normal range up to 125 nmol/L). High concentration of
vitamin D and its metabolites in decidua during the 1st trimester suggests its important role in the implantation process and a local immunological embryo-protection. On the other hand, evidence-based research did not prove a significant difference so far in ovulation stimulation or embryo development depending on
vitamin D level. In one of the publications, it was also found that
vitamin D binding protein (VDBP) has a molecular similarity to anti-sperm
antibodies, and another one concluded that both low (<50 nmol/L) and high (>125 nmol/L) concentration of
vitamin D are associated with decreased number and quality of spermatozoa in semen.
Vitamin D is definitely not a Trojan Horse in reproductive health, since there were no adverse effects reported for
vitamin D intake of up to 10,000 IU/day, but to proclaim it the Golden Fleece, more evidence is needed.