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.

PHYTOESTROGENS are polyphenolic non-steroidal plant compounds with estrogen like activity exerted through estrogen receptors. These receptors are distributed in several tissues such as male and female reproductive systems, bones, cardiovascular and central nervous systems. These natural phenolic compounds include isoflavonoids, flavonoids, lignans and stilbenes. Isoflavonoids are the most studied group of PHYTOESTROGENS, which can be found in the family leguminosae such as soybeans, alfalfa and clover. Daidzine and genistein are the principal isoflavonoids, which are found in plants as glycoside derivatives. These compounds can be metabolized in the digestive tract by normal microflora to their corresponding aglycones. The aglycones are absorbed through non-ionic passive diffusion. After absorption, they are readily conjugated with glucuronic acid and excreted in urine. Isoflavonoids have a good binding affinity for estrogen receptors (ER? and ER?) but they activate the intracellular mechanism (such as transcription and protein synthesis) less than steroidal estrogen. The estrogen receptor relative binding affinities of isoflavonoids when tested decreased in the following order: 17?-estradiol >coumestrol > genistein > equal >daidzien Nowadays, the relation between various diseases and estrogens are clearly identified. At menopause, the secretion of estrogens is reduced and as a result, osteoporosis, cardiovascular diseases (CVD) and menopausal symptoms occur. For the treatment of such conditions, estrogen is used but estrogen therapy may increase the risk of breast cancer. Isoflavonoids can be bonded to estrogen receptors and regulate LDL-receptor activity and can also suppress the osteoclasts in the bone tissue and reduce the risk of osteoporosis. Therefore, these compounds can be recommended to prevent the menopausal symptoms. Isoflavonoids can also be used in estrogen related cancers. These compounds may inhibit the 5?-reductase enzymes, decrease production of androgens, and so reduce the risk of prostate cancer. Furthermore, they can activate the estrogen receptors less than estrogenic compounds. Therefore, they can be used in estrogen-dependent breast cancers. In addition to enzyme inhibition activities, isoflavonoids at very high concentrations have anti-angiogenesis and antioxidant effects. The most important adverse effect of isoflavonoid is infertility syndrome in animals. The suppression of immune system is also reported. The aim of the article is to review the chemical structures, biological effects, therapeutic uses and adverse effects of PHYTOESTROGENS

Objective: Many different plants produce compounds that may mimic or interact with estrogen hormones in animals which are referred to as PHYTOESTROGENS. Materials and Methods: The two groups of PHYTOESTROGENS are the lignans and the isoflavones. PHYTOESTROGENS differ remarkably from synthetic estrogens in that they are easily broken down, are not stored in tissue, and spend very little time in the body. All in all, there are differing opinions about PHYTOESTROGENS role in health. When consumed as part of an ordinary diet, PHYTOESTROGENS are probably safe and beneficial. PHYTOESTROGENS through their effects on endocrine system could be a theraputic option for menopause and osteoporosis. Studies on cancer incidences in different countries suggest that PHYTOESTROGENS have antioxidant activity and can influence intracellular enzymes, protein synthesis, growth factor action, and cell proliferation which help protect against certain cancers (breast, uterus and prostate) in humans, in a way that makes them strong candidates for a role as natural cancer-protective compounds. More extensive studies are needed to confirm the PHYTOESTROGENS safety in different fields and determinig the kind and dose of related phytoestrogenic substance in each case. Besides the type and dose of phytoestrogen used, other factors such as duration of use, age, gender, genetic difference and general medical condition of the individual are determinants of positive effect of PHYTOESTROGENS.