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>.
So, how does one make sense of this mess of contadictory data? It should first be noted that 5AR inhibition has only been shown in vitro <87>, while it has not been observed in live animals – in fact, drastic increases in DHT have been found - and it seems that other constituents of green tea counteract the 5AR inhibition <88>. The conclusions of the first study, which found drastic decreases in body weight, testosterone, and other hormones, are very misleading. A drastic reduction in levels of all of the substances mentioned can unfortunately be expected from weight loss in any situation (which is one of the reasons losing weight without losing muscle mass is so difficult). Indeed, when the authors of the same study restricted the food intake of the rats to cause a similar weight loss to that induced by EGCG, similar effects were seen, implying that the changes were not due to EGCG but due to drastic body weight loss <22>. The effect green tea has on levels of androgens and other hormones is complex and depends on various factors, but no detrimental effects have as of yet been seen in human populations.
Just tell me where to send it.