The potentially negative effect of the "female" hormone estrogen has been the buzz with athletes lately. Increased estrogen may lead to increases in bodyfat and other maladies athletes want to avoid (Gyno, etc.) and many supplement companies have attempted to capitalize on this new found concern over excess estrogen levels.

For example, some research suggests that supplements such as androstenedione and a few of the other "andros" may increase estrogen levels by converting to estradiol (a powerful estrogen). Androgens such as testosterone and androstenedione convert to estradiol via and enzyme called "aromatase." Drugs or natural compounds that can block this enzyme are therefore called "anti-aromatase" agents.

Basically, there are two ways to affect estrogen. You can block the receptor site, or you can inhibit the enzyme (i.e. aromatase) that converts "male" hormones into "female" hormones (i.e. estrogens).

When a molecule fits into the receptor but does not send an estrogenic signal it is called an "antagonist" meaning it prevents or "blocks" estrogen from getting to the receptor but does not in itself act as an estrogen. Hence the term "estrogen blocker."

When something can lock into the receptor and does act as an estrogen, that is activates the receptor to one degree or another, it's called an "agonist." So, an antagonist fits into a receptor (thus blocking something else from occupying that receptor) but does not activate the receptor and an agonist fits into the receptor in question (in this case an estrogen receptor) and does activate the receptor to one degree or another.

This is exactly how the drug Tamoxifen works when treating breast cancer. It can fit into the estrogen receptor but does not activate it thus preventing estrogenic effects in the tissue in question.

Thus, Tamoxifen is an "estrogen antagonist." In truth, it's a bit more complicated then that as Tamoxifen is in fact both an estrogen antagonist or agonist depending in the tissue in question, which means it has mixed antagonist/agonist effects, but never mind...

So, what the reader should take away from the above is, you can block the effects of estrogen by either blocking the receptor it fits into, or inhibit the enzyme the body uses to convert androgens into estrogens. Got all that?

Chrysin has been marketed as just such an anti-aromatase, or enzyme inhibitor. Chrysin is sold alone, or often added to andro supplements, in hopes it will prevent any estrogen production that may result from taking andro products. Chrysin is a bioflavonoid similar to other flavonoids such as Quercetin.

There are many different types of flavonoids with a wide range of effects. In vitro (test tube) research has shown Chrysin is a powerful inhibitor of the aromatase enzyme and may have other health uses.

There in lies the problem. To date, no solid studies using Chrysin outside a test tube have been done. That is, no studies in walking, talking, human beings have been carried out to show that Chrysin indeed has this effect and at what doses are needed to reduce estrogen levels. Most troubling perhaps is the fact that bioflavonoids such as Quercetin, and possibly Chrysin, are notoriously difficult to absorb during digestion and very little gets through.

So, a large question still remains about whether or not Chrysin will be of any use as an estrogen reducing supplement in hard training athletes or what the actual dose is needed.

Only time and more research will tell. In truth, I have yet to see anyone who derived any benefit from this supplement. For reducing estrogen in athletes it gets a big thumbs down.

Kellis, J.T. and L. E. Vickery Jr. "Inhibition of human estrogen synthetase (aromatase) by flavones," Science 225/4666 (1984), p. 1032-4.

Pelissero, C. and M. J. Lenczowski, et al. "Effects of flavonoids on aromatase activity, an in vitro study," Jour. Steroid Biochem. Mol. Biol. 57/3-4 (1996), p. 215-23.

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