Researchers at Kingston University in England have discovered that phenols in red wine inhibit the enzyme that removes testosterone from the body. Quercetin in particular may be an effective testosterone booster.
The enzyme that the Brits are studying goes by the name of UGT2B17. It's a steroid glucuronidation enzyme, which means it attaches molecules to testosterone, which enables the body to eliminate testosterone through the urine. Because doping tests for testosterone examine urine, substances that inhibit UGT2B17 are of interest to chemical athletes who use testosterone. We already know that ibuprofen, diclofenac and EGCG are UGT2B17 inhibitors.
It may be that naturally occurring UGT2B17 inhibitors are also of interest to natural athletes. Supplements containing tea extracts may be capable of causing a temporary rise in the testosterone level. A raised testosterone level during and after a training session may speed up recovery.
The Brits say in their study, which will soon be published in Nutrition Journal, that red wine inhibits the transformation of testosterone by UGT2B17 in test tubes.
After the researchers had worked out that the effect was not due to the alcohol, they used high performance liquid chromatography to work out which substances found in red wine were likely to inhibit UGT2B17. They found five candidates. In the chromatogram above 1 stands for gallic acid, 2 for chlorogenic acid, 3 for caffeic acid, 4 for p-coumaric acid and 5 for quercetin.
When the researchers did in-vitro tests to work out how good the substances were at preventing UGT2B17 from converting testosterone, they saw that quercetin in particular was a good UGT2B17 inhibitor. The researchers suspect that quercetin takes the place of testosterone in UGT2B17.
"It has yet to be determined if any direct inhibition of steroid glucuronidation enzymes could alter the levels of circulating serum testosterone in addition to altering the levels of testosterone excreted in urine", the researchers write. "The ubiquitous presence of quercetin and other active flavonols, along with the catechins, in many foodstuffs indicate that any in vivo effects may be common."
Nutr J. 2012 Sep 7;11(1):67. [Epub ahead of print].