Soy does not affect testosterone levels

For quite some time, ardent supporters of whey, egg, and casein protein as muscle-builders have more or less shunned soy protein, believing that it had negative effects on testosterone levels. This myth was put to rest by a recent study conducted by Miami Research Associates, which showed that soy protein (both concentrate and isolate) did nothing of the sort.

In addition, the study revealed that soy protein did not interfere with, or increase, estrogen levels. This further supports the conclusion that soy is a great protein source for men. In fact, other studies have shown that protein blends that include soy may actually produce a greater degree of lean muscle growth than any single-ingredient protein.

So, fear not, musclemen. Soy is not the enemy you may have once thought it was.