So, I've been slowly looking for scientific documentation of the impact of the soy/estrogen connection that people keep mentioning, and I'm coming to believe that it isn't really a major factor. Most of the articles stating that there is a problem don't have credible citations to reputable scientific sources. I even found one site asserting that eating soy makes people gay. psaw.
As best as I can tell:
1) components of soy definitely have a chemical structure that makes them function as
very weak estrogens.
2) estrogen is in your body anyhow
3) you would have to eat absolutely massive quantities of soy for it to have any impact.
4) there may actually be an opposite effect - the weak estrogens from soy locate themselves in estrogen receptor sites within your body, and actually reduce the impact of your body's own fulll-strength estrogen. (now, of course, I wish that I could find the article that I read that said this, as I'm now guilty of doing the same thing - posting something without adequate scientific backup).
5) even if it does increase estrogen levels, regardless, testosterone helps with muscle gain, estrogen doesn't displace nor negate that.
For example, WebMD has this to say:
Soy protein is as effective as most animal sources of protein, although many male athletes think of it as a "girl's protein," Antonio says. "But this is where public perception and scientific reality clash." Research doesn't support the fears that soy protein lowers blood levels of testosterone or reduces lean body mass.
from the last page of this posting:
http://www.webmd.com/diet/protein-shakes with a whole list of citations.
So, I'd be interested in actual scientific data that demonstrates there to be a problem with soy causing an increase in estrogen, then subsequently, interfering with muscle gain or other body systems. Most sites seem to be mens-health or body building oriented, asserting there is a problem, largely parroting one another, but not providing one iota of proof. I suggest that there may be an urban-legend sort of effect here at work, based on partial scientific information.