Vitamin D and Testosterone in Healthy Men: A Randomized Controlled Trial
What this study found
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.
- Study & population
- Randomized, double-blind, placebo-controlled, single-center trial at the Medical University of Graz, Austria.
- Intervention
- Vitamin D3 (Oleovit D3 drops), 20,000 IU orally once weekly for 12 weeks, equivalent to about 2,857 IU/day.
- Key limitation
- Small, single-center study in healthy men, which limits generalizability.
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Open PDFOriginal abstract
Context: Available evidence shows an association of vitamin D with androgen levels in men. However, results from preliminary randomized controlled trials (RCTs) are conflicting. Objective: To evaluate whether vitamin D supplementation increases total testosterone (TT) levels in healthy men. Design: The Graz Vitamin D&TT‐RCT is a single‐center, double‐blind, randomized, placebo‐controlled trial conducted between December 2012 and January 2017. Setting: Endocrine outpatient clinic at the Medical University of Graz, Austria. Participants: Ninety‐eight healthy men with TT levels ≥10.4 nmol/L and 25‐hydroxyvitamin D [25(OH)D] levels <75 nmol/L completed the study. Intervention: Subjects were randomly assigned to receive 20,000 IU/wk of vitamin D3 (n = 50) or placebo (n = 50) for 12 weeks. Main Outcome Measures: Primary outcome was TT measured using mass spectrometry. Secondary outcomes were free testosterone, sex hormone‐binding globulin, estradiol, follicle‐stimulating hormone, and luteinizing hormone levels; free androgen index; metabolic characteristics; and body composition. Results: In healthy men [mean values ± standard deviation: age, 39 years (±13 years); 25(OH)D level, 53.3 nmol/L (±18.3 nmol/L); TT, 19.1 nmol/L (±5.6 nmol/l)], no significant treatment effect on TT was found; however, there were significant effects on quantitative insulin sensitivity check index (QUICKI) and a trend toward decreased Matsuda index. In the treatment group, median (interquartile range) changes for TT, QUICKI, and Matsuda index were 0.5 nmol/L (−0.63 to 0.63 nmol/L; P = 0.497), −0.02 (−0.04 to 0.01; P = 0.034), and −0.9 (−3.2 to 0.8; P = 0.051), respectively. Conclusion: Vitamin D treatment had no effect on TT levels in middle‐aged healthy men with normal baseline TT, but it significantly decreased QUICKI. Additional studies investigating vitamin D effects on TT and insulin sensitivity in healthy men are required.