Does soy cause feminization in men?

Because soy contains estrogen-mimicking isoflavones, some consumers believe consuming soy will lead to feminization in men. There are many studies on this topic, but most used rodents or other non-human primates as test subjects. But animals metabolize soy differently than humans, so those studies are inaccurate representations of soy’s effects on humans.

In scientific studies on human males, researchers found:

• Soy had no effect on estrogen levels in men who consumed up to 24 servings (150 mg) of soy a day for up to six months.
• Soy increased strength and lean tissue in resistance exercises as effectively as beef.
• When mixed with milk proteins, soy has shown to successfully repair muscles.