Context: Results of animal models and cross-sectional cohort studies have suggested a beneficial role for vitamin D in male reproduction.
Objective: Determine the effect of vitamin D and calcium supplementation on semen quality in infertile men with serum 25-hydroxyvitamin-D (25OHD) levels ≤50 nmol/L.
Design: A single-center, triple-blinded, randomized clinical trial.
Participants: A total of 1427 infertile men were screened to include 330; 1002 men did not meet inclusion criteria and 95 did not wish to participate.
Intervention: The active group received cholecalciferol 300,000 IU initially, then 1400 IU cholecalciferol and 500 mg of calcium daily for 150 days; the other group received placebo.
Results: Serum concentrations of 25OHD and 1,25-dihydroxyvitamin D3 were significantly higher in men in the treatment group compared with the placebo group. Vitamin D supplementation was not associated with changes in semen parameters, although spontaneous pregnancies tended to be higher in couples in which the man was in the treatment group [7.3% vs 2.4%, Δ5.0% (-0.6%; 10.5%)]. Vitamin D treatment in a subgroup of oligozoospermic men increased the chance for a live birth compared with placebo [35.6% vs 18.3%, Δ17.3% (1.6%; 32.9%)]. Moreover, serum inhibin B levels were higher in men deficient in vitamin D who were randomly assigned to receive high-dose vitamin D [193 pg/mL vs 143 pg/mL, Δ49 pg/mL (8; 91 pg/mL)]; however, the increase in sperm concentration was not significantly higher than in the placebo group (P = 0.07).
Conclusion: High-dose vitamin D supplementation did not improve semen quality in vitamin D-insufficient infertile men. The positive impact of vitamin D supplementation on live birth rate and serum inhibin B in oligozoospermic and vitamin D-deficient men may be of clinical importance and warrant verification by others.
Trial registration: ClinicalTrials.gov NCT01304927.