Vitamin D levels and human sperm DNA fragmentation: a prospective, cohort study

Intracytoplasmic sperm injection (ICSI) has revolutionized the treatment of couples with male factor infertility but results remain suboptimal and suggest the need for further investigation into the molecular biology of spermatozoa. Vitamin D has been implicated in spermatogenesis and sperm function. Hypovitaminosis D has been associated with abnormal testicular function, including elevated sperm DNA fragmentation in a murine model. This study's objective was to evaluate if there is a correlation between Vitamin D sufficiency and human spermatozoa DNA fragmentation index % (DFI%) in infertile couples.

A prospective cohort study using a consecutive, convenience sample of subjects with infertility. The primary endpoint was the effect of Vitamin D sufficiency on human spermatozoa DFI%, and secondary outcomes included Vitamin D's effect on moderate DFI%, high DFI%, High DNA stainability % (HDS%), sperm density (million/mL), sperm total motility (% total) and sperm strict morphology (% total). Of the 111 participating, 9 were excluded, leaving 102subjects. The subjects were stratified by vitamin D levels: deficient (< 20 ng/mL; n = 24), insufficient (20-30 ng/mL; n = 43),, and sufficient (> 30 ng/mL; n = 35). There were no statistical difference between the categories of serum vitamin D levels and sperm DFI% as well as the secondary outcomes. An increased BMI was associated with low serum vitamin D levels (p = 0.0012).

Vitamin D deficiency was not associated with sperm DFI% or routine sperm parameters. Previous animal and human studies have demonstrated conflicting results between sperm parameters and Vitamin D levels. Redundant pathways in Vitamin D and calcium homeostasis in the human male reproductive tract may maintain essential reproductive processes during Vitamin D insufficiency or deficiency.

Trial Registration Number: MOD00002311 (ClinicalTrials.gov).