Haven't Googled it up but from what I understood these mimic hormones in the body. I remember years ago there was some similar sort of paranoia among men about legumes. Some people claimed that phytoestrogens act like regular estrogen in the body, meaning mean shouldn't be eating much of it in danger of feminizing effect. I believe people are still arguing about this since I saw one vid about it in nutrition channel I'm subbed just recently.