Study: vitamin D increases testosterone levels

If this has been posted before feel free to delete/move this thread.

I ran into this study (December, 2009) that found a correlation between vitamin D- levels and amount of testosterone.

Here is the summary, there's a link to the full article:
http://www3.interscience.wiley.com/j...27538/abstract (WFS)

From what I understood:
- The researchers routinely measured the amount of vitamin D, testosterone, free androgen and SHBG (Sex hormone-binding globulin) in 2299 men through 1997-2000
- Men who had sufficient vitamin D levels had significantly higher testosterone and free androgen index and lower SHBG levels
- Some of the men were using their own vitamin supplementation which included vitamin D, but their testosterone levels were only slighly higher than normal
- Testosterone and androgen levels showed a strong seasonal correlation. The levels were lowest in March and highest in August.
- Of the participants 11.4 % were sufficient, 25.6 % insufficient, 43 % moderately deficient and 19.9 % serevely deficient in vitamin D levels
- 18 % had hypogonadism (very low testosterone), their vitamin D levels were significantly lower than mean values
- In the introduction-chapter the researchers state that vitamin D is mainly produced in the skin and nutrition/supplementation only plays a minor role (this statement is quoted from a previous study which I have not read)

Testosterone enhances muscle development, strength, and endurance. Is increased testosterone the reason vitamin D improves performance (or performance is increased in the summer)?

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It sounds like they mainly found correlation, not causation.

In other words, testosterone and Vitamin D levels may be associated, but that's not the same thing finding that vitamin D supplementation will cause higher testosterone levels, especially with a statement like the following: "Some of the men were using their own vitamin supplementation which included vitamin D, but their testosterone levels were only slighly higher than normal"

Still, interesting stuff (and yet ANOTHER reason that whole milk, which contains fat soluble vitamin D that is readily absorbed, may be better than steroids for novices, haha). Thanks for posting it. I hope this spurs more, similar, research.


http://board.crossfit.com/showthread.php?t=56831