Vitamin D and Testosterone in Healthy Men: A Randomized Controlled Trial

Randomized, double-blind, placebo-controlled, single-center trial at the Medical University of Graz, Austria. Healthy middle-aged men with low vitamin D status and normal baseline total testosterone were enrolled; the vitamin D arm had median age 34 years, median BMI 25.0 kg/m2, baseline total testosterone 18.7 nmol/L, and baseline 25(OH)D 52 nmol/L.

Vitamin D3 (Oleovit D3 drops), 20,000 IU orally once weekly for 12 weeks, equivalent to about 2,857 IU/day. The active arm received 50 oily drops weekly; placebo was used as comparator in this randomized trial.

Vitamin D supplementation did not increase total testosterone in healthy men. In the vitamin D group, total testosterone changed from 18.7 to 19.4 nmol/L (change 0.5; within-group P=0.497), and the between-group difference was not significant (P=0.922). Vitamin D status improved substantially, with 25(OH)D rising from 52 to 107 nmol/L by study end (P=0.001). Overall, the trial found no clear testosterone benefit from vitamin D in this cohort, although other endocrine and insulin-sensitivity changes were reported in the broader paper.

Small, single-center study in healthy men, which limits generalizability. The intervention was short-term (12 weeks, with additional follow-up reported in the paper), and baseline total testosterone was already in the normal range, reducing the chance of detecting a meaningful increase. Findings are specific to men with relatively low vitamin D status and do not establish benefit in other populations.