A concern that is commonly brought up about green tea is the idea that it decreases levels of androgens such as testosterone and DHT. One study reported that after administered to rats, EGCG "significantly reduced food intake; body weight; blood levels of testosterone, estradiol, leptin, insulin, insulin-like growth factor I, LH, glucose, cholesterol, and triglyceride" [22]. However, a different study with green tea catechins in rats found decreased body weight but increased thyroid stimulating hormone (TSH), LH, and testosterone levels [85]. A final study in mice with green tea indicated drastic increases in both testosterone and DHT from green tea treatment, but levels of both were synergistically inhibited when it was adminstered along with soy phytochemicals [86]. In vitro, EGCG inhibits type I 5AR [2, 87], which is partially responsible for the conversion of testosterone to DHT (for this reason, it has been proposed in the topical treatment of acne and hair loss [2]), while in rats, green tea is an aromatase inhibitor, which (in theory) would be responsible for an increase in tesotsterone levels [85].
