Supplementation with vitamin D does not increase serum testosterone levels in healthy males.
Level 2 - randomized trial
Secondary analysis of multiple randomized controlled trials alongside a cross-sectional study
PubMed 23686706 · doi:10.1055/s-0033-1345139
What was done
A cross-sectional study in 893 males was combined with pooled secondary data from 4 randomized controlled trials: 3 trials testing vitamin D (20,000 to 40,000 IU per week vs. placebo for 6–12 months, n=282) and 1 trial testing testosterone undecanoate (1,000 mg injections vs. placebo over 1 year in men with baseline testosterone <11.0 nmol/L, n=37). Serum 25(OH)D and androgen levels were measured at baseline and study endpoints.
What was found
In the cross-sectional analysis (n=893), serum 25(OH)D was a statistically significant positive predictor of serum testosterone (no specific effect sizes or p-values reported in abstract). In the randomized trials (n=282), vitamin D supplementation showed no significant effect on total or free serum testosterone. In the testosterone trial (n=37), testosterone therapy had no significant effect on serum 25(OH)D. Subgroup analyses restricted to men with low baseline 25(OH)D or testosterone levels also showed no significant treatment effects.
Why it matters
Observational associations between vitamin D and testosterone appear to be non-causal in both directions. High-dose vitamin D supplementation does not raise testosterone in men without severe baseline vitamin D deficiency.
Limits
This was a post-hoc secondary analysis of trials originally powered for other endpoints (weight loss, insulin sensitivity, depression, and body composition). The abstract provides no exact numerical values, confidence intervals, or p-values. The testosterone intervention trial had a very small sample size (n=37), and participants with severe vitamin D deficiency were not specifically isolated.
Cited by
- contradicts Correcting clinical deficiencies in vitamin D, zinc, and magnesium can result in an incremental increase of 100 to 150 ng/dL in total testosterone.