Yes, and no. Tofu is made from soy beans. Soy is a phytoestrogen, or a plant based estrogen. It contains two isoflavones, genistein and daidzein, which act like estrogen (the female sex hormone) within the body. Because estrogen plays a role in everything from breast cancer to sexual reproduction, it has come under scrutiny and concern. There hasn't been a lot of research on this, but it doesn't appear that tofu has any negative impact on testosterone levels and may - may - reduce the risk on prostrate cancer.