I have been using Soy protein for years. For every study that shows the supposed increase in estrogen levels, there are 10 others that do not support this science. Supposedly Soy also helps fight of prostate cancer in males...
One of my original questions (years ago) was this: Does soy protein contain the essential amino acid profile? Yes, it does. Leucine was the one I was concerned about.
As the years go on, I find myself using a mix of Soy and Whey. I don't really notice much difference. The biggest difference I notice is in comparing protein drinks to good ol' solid food. My testosterone levels on soy are currently over 660 ng.per dl. I am 46. I weigh 200 lbs. and am at 11-12% bodyfat. I am not "chemically enhanced"
Here is some quick research for the negative stuff. As previously stated, there are also many prestigious controlled studies done to refute the negativity around soy. I think I harden up a little more when I am only using Whey. I don't really like using soy exclusively, but there are times on the road when I can go into the grocery store and easily buy cold organic soy to last me a couple of days. It's a hell of a lot cheaper than buying a 4 Pack of Muscle Milk (which I also like for the more "filling" effect when I'm in a hurry)
Tough to say. I have been a fan of Pearl's for years. He did fine, but he was never shredded and ripped. He was also enhanced at a few key points in his career. I say: Try it yourself and see what you think. Whatever happens is so subtle it's almost impossible to detect.
According to the research at
http://www.solae.com/company/soyessentials/soyprotein.html, Soy protein provides adequate amounts of all the essential amino acids. This information is listed on the web site of a company that sells soy products, which may make it less than 100% objective. However, the information is corroborated on other web site, such as
http://faq.aces.uiuc.edu/faq.pdl?project_id=5&faq_id=74, which refers to a 1989 study by Erdman & Fordyce.
nearly 75% of all processed foods have soy products in them. What’s more, there is NO labeling laws for soy, even though it is one of the eight most common allergens! The mayo clinic seems to think that allergens are always labeled (see
http://www.mayoclinic.com/health/food-allergies/AA00057), but that isn’t always the case, particularly with soy. Things that don’t sound like soy, like "dextrose," and "lecithin" are often made from soy protein. What’s worse, "natural flavors" can be made of soy, or not. So people with soy allergies have to avoid it, just in case.
So even if you don’t think you’re eating soy, you are probably getting a lot of it without realizing.
In addition to being a common allergen, the problem with Soy is that it contains phytoestrogens, which "mimic the physiological effects of the endogenous hormone, estrogen". So by eating soy, you’re really pumping hormones into your body that you may not need. As the web site (listed below) puts it, "Because of their estrogenic effects, they act more like drugs in the body than foods." If your body needs estrogen, that may be fine. But for men, or pregnant (particularly vegetarian) mothers, there is evidence that even a very small amount of soy may contribute to problems such as low sperm counts or even testicular cancer and birth defects. See
http://thehealthyskeptic.org/soy-foods-associated-with-lower-sperm-counts/ for more information.
And soy may have other negative effects, such as early menstruation in girls, limiting the body’s absorption of essential minerals (due to higher levels of phytic acid than found in nearly any other food), and a number of other potential ill effects. See
http://www.second-opinions.co.uk/no-joy.html,
http://www.alkalizeforhealth.net/earlymenarchy.htm,
http://findarticles.com/p/articles/mi_m0KGB/is_/ai_n6006183.
