RE: Soy Protein and Testosterone
The problems with trying to get qualitative and quantitative information on this issue are:
1) there are different types of soy products (the ones we're eating now are relatively new, not the traditional type)
2) There are 2 main types of phytoestrogen involved and they have different actions.
3) There is a certain amount of processing in the gut - everyone has slightly different gut flora and this alters it.
4) The effects differ on from between men and women and between individuals greatly.
If you look at a lot of research it says there is little effect and anecdotally many people agree. However as an example to make you think; if it were all overblown nonsense why would the medical community (specialists like oncology registrars, not quack therapists) strongly recommend that women is insulin sensitive tumors* avoid soy products. Why? Because there is a great deal of evidence to support the theory that in this example soy can have a profound estrogen type effect.
The fact is this, soy is used all over the place in foods and the long term effects of the newer minimally processed types of product is not understood. Not even a little. That;s before you considered it in conjunction with all the other xenoestrogens present in water, plastics, glues etc.
It all comes down to this: variety. You can have soy but you shouldn't rely on it - this is the same for most foods.
*these are breast tumors in post menopausal women who produce very little estrogen, the rate of tumor growth is increased by estrogen.