The male reproductive tract has been identified as a target tissue for vitamin D, and previous data suggest an association of 25-hydroxyvitamin D [25(OH)D] with testosterone levels in men. We therefore aimed to evaluate whether vitamin D supplementation influences testosterone levels in men. Healthy overweight men undergoing a weight reduction program who participated in a randomized controlled trial were analyzed for testosterone levels. The entire study included 200 nondiabetic subjects, of whom 165 participants (54 men) completed the trial. Participants received either 83 μg (3,332 IU) vitamin D daily for 1 year (n = 31) or placebo (n =2 3). Initial 25(OH)D concentrations were in the deficiency range (< 50 nmol/l) and testosterone values were at the lower end of the reference range (- nmol/l for males aged 20-49 years) in both groups. Mean circulating 25(OH)D concentrations increased significantly by nmol/l in the vitamin D group, but remained almost constant in the placebo group. Compared to baseline values, a significant increase in total testosterone levels (from ± nmol/l to ± nmol/l; p < ), bioactive testosterone (from ± nmol/l to ± nmol/l; p = ), and free testosterone levels (from ± nmol/l to ± nmol/l; p = ) were observed in the vitamin D supplemented group. By contrast, there was no significant change in any testosterone measure in the placebo group. Our results suggest that vitamin D supplementation might increase testosterone levels. Further randomized controlled trials are warranted to confirm this hypothesis.
In the new study, green and white tea definitely inhibited UGT—by 18 percent and 30 percent, respectively. The green tea was provided as a liquid, while the white tea was a concentrated powder extract, which explains the difference in potency. When the individual polyphenol compounds in the tea were tested, however, the potency rose considerably—epicatechin showed an percent inhibition of UGT, while EGCG showed a percent inhibition. It should be noted, however, that tea polyphenols are rarely absorbed orally in such great amounts; instead only a small percentage is actually absorbed. If tea polyphenols were completely absorbed, all “testosterone-boosters” would be full of them. Still, there is enough in tea to affect the functioning of UGT and, consequently, the results of a testosterone drug test.