The info I have is in some of my book. You can also find allot about it in muscle development. It lower both sex hormones. but in men lowering test will make estrogen rise.
Here is one web site that has some info.Invalid Link Removed
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Possible side effects and precautions
Green tea, even in large amounts, is associated with very few side effects. In mice, signs of toxicity were only observed when doses reached 2 g/kg daily of an 80% polyphenol abstract (this is about the equivalent of 8 cups per pound of body weight, per day – 1200 cups of tea in a 150 lb. individual) [80].
It is possible that large amounts of polyphenols could impair mineral absorption, making extra mineral supplements a wise course of action. Of primary importance is a significant inhibition of nonheme iron absorption, which is relevant if most of your iron comes from sources other than meat [81, 82]. It is possible that there is also mild inhibition of calcium, manganese, and zinc [83, 84], although there is a study that disputes the finding of impaired zinc absorption [84]. The only place where the phenomenon of significant mineral blockage by green tea has even been of worry is in Tunisia, where there is high tea intake and non-meat products are the primary source of dietay iron [81]. However, it may be prudent to take a multivitamin supplement that provides adequate amounts of these minerals at a separate time or a low-dose slow release iron supplement if one decides to consume large amounts of polyphenols.
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. "
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In addition to decreased food intake and body weight, rats injected with EGCG had lower levels of testosterone (70 percent less in the bloodstream) and insulin. "These results may not have been a direct result of EGCG since food restriction could also cause these hormones to drop," said Liao.
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