Isoflavones are a type of phytoestrogen found in high amounts in soy foods. Genistein is one of the most metabolically active isoflavones. Soy isoflavones, including genistein, have a weak estrogenic activity in the body that can be either agonistic or antagonistic. In other words, phytoestrogens can either mimic or block the effect of estrogen. Soy isoflavones can reduce the incidence of menopausal hot flashes, and also can help maintain a healthy prostate gland in men.