I just was looking at The NSCA Strength and Conditioning Journal and there was a study on 3 groups: 1 group weight trained and consumed 3 soy protein bars, the next consumed whey protein bars, and the last consumed no protein bars. Each group lifted weights in the same format.
It was determined that the soy and whey protein groups increased lean muscle mass while the group who just lifted without any proteinbars did not increase mass.
Jose Antonio suggests that soy is equal in value in adding muscle mass. If this is true, is there a negative effect from soy as in estrogen production or is that really just a myth?