Researchers at Kingston University in London have discovered that drinking green tea or white tea can help steroid-using athletes beat a commonly used anti-doping test. Declan Naughton and colleagues reported that compounds known as catechins may allow athletes to use the anabolic steroid “testosterone” and avoid detection.

The testosterone:epitestosterone ratio (T:E ratio) test is frequently used to screen drug-tested athletes for the exogenous administration of testosterone. It determines the ratio of testosterone glucuronide to epitestosterone glucoronide in an athlete’s urine.

Exogenous administration of testosterone does not influence the levels of epitestosterone. Therefore, a testosterone-using athlete should have a higher ratio of testosterone metabolites in their urine when compared to epitestosterone.

The catechins found in green tea inhibit an enzyme called UGT2B17. This enzyme is responsible for attaching glucuronic acid to testosterone. By inhibiting UGT2B17, an athlete will excrete less testosterone glucoronide in their urine. This will help a testosterone-using athlete produce a normal ratio.

Most individuals have a ratio of 1:1 testosterone to epitestosterone. But ratios as high as 4:1 are not uncommon. The World Anti-Doping Agency (WADA) considers a ratio of 4:1 to be a putative indicator of doping subject to confirmation by another anti-doping procedure known as carbon isotope ratio (CIR) testing.

The T:E ratio test can not tell the difference between testosterone produced by the body and testosterone that has been introduced via injections, pills or creams.

CIR testing can detect exogenous testosterone of plant origin. However, if athletes are able to successfully pass the T:E ratio test, they are not subject to the more definitive CIR test.

Therefore, if athletes can avoid detection in the T:E ratio test, they can get away with the administration of exogenous testosterone.