Effects of vitamin D supplementation on androgens in men with low testosterone levels: a randomized controlled trial.
Level 2 - randomized trial
Double-blind randomized placebo-controlled trial
PubMed 30460609 · doi:10.1007/s00394-018-1858-z
What was done
The Graz Vitamin D&TT-RCT was a single-center, double-blind, randomized placebo-controlled trial conducted in Austria. A total of 100 healthy men with low baseline total testosterone (< 10.4 nmol/l) and vitamin D levels < 75 nmol/l were randomized to receive either 20,000 IU of vitamin D3 per week (n = 50) or placebo (n = 50) for 12 weeks. The primary outcome was serum total testosterone measured by mass spectrometry. Secondary outcomes included free testosterone, free androgen index, sex hormone-binding globulin, estradiol, follicle-stimulating hormone, luteinizing hormone, metabolic characteristics, and body composition. Ninety-four men (mean age 47 ± 12 years; baseline 25-hydroxyvitamin D 56.3 ± 18.3 nmol/l) completed the study.
What was found
The abstract reports no significant treatment effect of vitamin D3 supplementation on serum total testosterone or on any of the secondary outcome variables. No numerical post-treatment values, effect sizes, confidence intervals, or p-values are reported in the abstract.
Why it matters
Observational studies have suggested a link between vitamin D and androgen levels, but this trial demonstrates that short-term vitamin D3 supplementation does not raise serum testosterone in middle-aged men with low baseline levels.
Limits
The study had a relatively small sample size (n = 100 randomized, 94 completed), a short 12-week intervention duration, and was performed at a single outpatient center. The abstract lacks specific numerical values and effect estimates. Participants had mild-to-moderate insufficiency rather than severe vitamin D deficiency at baseline, so findings may not generalize to severely deficient cohorts.
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.