In an earlier blog, I discussed how vitamin D is not just a fat-soluble vitamin but a precursor hormone that allows the body to produce a steroid hormone called calcitriol, which can shield us from many different ailments, including seasonal affective disorder, or SAD.
This time around, I want to talk about how researchers have also discovered that the male reproductive tract is a target tissue for vitamin D, and that a link or association exists between a man's level of 25-hydroxyvitamin D (25 OH vitamin D) and the level of testosterone in his bloodstream. (More about women's testosterone levels in a bit.)
Men with and without enough vitamin D
An article published this March in the journal Hormone and Metabolic Research described a study of non-diabetic men (aged 30-49 years) participating in a randomized, placebo-controlled trial in which the men received either 3,332 international units of vitamin D daily for 1 year (31 total subjects), or a placebo (23 subjects). (International units--IUs--are a measure of biological activity rather than of quantity.)
All during the year of the study, the scientists analyzed each man's blood levels of testosterone and of 25 OH vitamin D. Initially, they found that the vitamin D levels of all participants were suboptimal and that both groups' testosterone levels were also at the lower end of the suggested range.
Are levels of vitamin D related to levels of testosterone?
But after a while, as the mean 25 OH vitamin D levels in the vitamin-D group gradually increased to healthier levels, the total testosterone levels of this group increased significantly. The placebo group's low levels of vitamin D remained unchanged and, not surprisingly, so did their testosterone levels.
The researchers said that although their findings certainly suggest that supplemental vitamin D increases testosterone levels, in order to confirm this connection they will need to conduct additional controlled trials.
So, if you've ever wondered whether your testosterone levels were decreasing--because, say, you've noticed lately that your sex drive (libido) has been waning--consider asking your doctor to check your testosterone level and your levels of vitamin D.
And the women too!
And, by the way, women have significant levels of testosterone in their bodies, too, just not as much as men do. This means that a vitamin-D deficiency can greatly affect the moods and libidos of women too.