Epidemiological studies suggest that populations consuming a diet of high phytoestrogens, have a lower risk of many of the so-called “western” diseases.Phytoestrogens are naturally found in many foods and their biological activity is confirmed in animals, in different studies. Phytoestrogen consist of a number of classes, including lignans, isoflavones, coumestans and resorcylic acid lactones. Soy products have phytoestrogens such as genistein, diadzein and glycetin that all of them are from isoflavon class. These isoflavones affect estrogen receptors and have both agonist and antagonist properties. Isoflavone have agonist property when estradiol is low for competition to receptor attaching. Antiestrogenic effects of phytoestrogens depend on their partial concentration and endogenous estrogen, so, when endogenous estrogen is high, phytoestrogens may release estradiol from its receptors. In menopausal period that estrogen is low, phytoestrogens have estrogenic effects. Phytoestrogens prevent menopausal period symptom such as hot flush, vaginal drying, osteoporosis, cardiovascular disease and decrease incidence of breast, colon, endometrial and ovarian cancers.