Soy, block

Okey, soy contains phytoestrogens (estrogens from plants). phytoestrogens are not as potent as the most potent estrogen, estradiol. As we know men have fewer estrogen receptors than women… so higher levels of phytoestrogens compete with the female hormone (estrogen) for receptor sites (and) block its actions. Susan Kleiner, Ph.D, RD, author of Power Eating, notes that if you want to block estrogen, take moderate amounts of isoflavones. Sounds reasonable, what do you guys think? (Btw. I still won’t eat soy, I just wanted to bring this up)

Cy Wilson already wrote about this, check it out

These two villains bind readily to Estrogen Receptors. One such receptor is the Alpha receptor and the other, of course, is the Beta receptor. The Alpha receptor is the one generally associated with breast tumors, increased body fat, water retention, etc. The Beta receptor really isn’t something to worry about. Anyhow, genistein and daidzein can bind rather well to the Alpha receptor.

No big deal right? Well, it might actually be somewhat beneficial if they didn’t activate transcription to any significant degree, as this would be what’s considered an anti-estrogenic action. In other words, it would be good if the compound binded to the site and didn’t cause any growth, while preventing any naturally-produced estrogen from binding (the estrogen “parking spots” would already be filled). However, genistein does activate transcription to a significant degree after binding to the Alpha receptor and therefore will cause growth of tissues.(1,2,3)

It’s fairly clear that soy protein lowers testosterone levels. How does it affect estrogen and progesterone levels? You’d figure that genistein would at least reduce the activity of estrogen to some extent, since it binds at the same receptor site, right? Well, apparently not. It turns out that genistein does not inhibit the effects of estradiol and in fact has been demonstrated to exert an additive effect when combined with estradiol.(2,8)

This means that they don’t interfere with one another and can both exert the same negative effects at the same time, thus, packing a double punch. Furthermore, genistein may potentially increase estradiol levels as well. It’s thought that this may occur because genistein may deconjugate estrone in the gut and allow for it to reabsorb into the bloostream and convert to estradiol.(9)

It’s possible that it may also exert some progestational activity.(10) Even worse is that the estrogenic activity of these phytoestrogens may have been underestimated in the past, as there is evidence that they may be much more potent in vivo as opposed to in vitro [test tube] studies.(11) Oh, and while we’re still on the topic or hormones, soy protein has also been shown to decrease IGF-1 concentrations in male rats.(12) Oh, and I’d feel bad if I forgot to mention that it can lower T4 levels, too.(13)

I understand all the bad rap soy gets here at T-Mag, and I’m sure it deserves it. I’m always skeptical of things that get hyped in women’s mags, the same mags that are always harping about the food pyramind and how bad protein is (though I sense the tide beginning to turn on protein!).

These same mags are always saying how soy may help prevent breast cancer, citing the incidence of breast cancer in Asian women eating lots of soy. My question is this: if soy is so estrogenic, why are Asian women so tiny? They just don’t seem to have near the problem of being fat. They eat tons of fried foods too! The one thing they eat very little of, from what I understand, is refined flour.