Soy Isoflavones Reduce DHT, Increase Testosterone Soy isoflavones reduce DHT and increase testosterone levels in rats Soybeans contain the isoflavones genistein and daidzein. (Photo by T. Hagihara) There's a lot of speculation on how soy intake and hair growth are related, so in a series of posts beginning with this one, we'll be taking a look at what the studies have to say. Hopefully, it will become clear whether soy isoflavones really do anything, how much isoflavones is the optim