Does soy have feminizing effects on men?
Soy contains isoflavones, which have potentially estrogenic effects. This has raised the concern that men consuming soy might experience adverse hormonal changes. A recent meta-analysis (systematic examination of multiple studies) by Johns Hopkins University researchers found that neither soy foods nor isoflavone supplements significantly alter testosterone levels in men [1]. Of interest to the athletic population, 12 weeks of supplementation with soy protein did not decrease testosterone levels or hinder lean body mass gains in men engaged in a resistance training program [2]. Therefore, the evidence does not support the idea that soy is likely to cause feminizing effects in men.
