Beneficial and Adverse Effects of Dietary Estrogens on the Human Endocrine System: Clinical and Epidemiological Data

Dietary estrogens, also known as phytoestrogens, represent a family of plant compounds which are of biological interest because they exhibit both in vivo and in vitro weak estrogenic and anti-estrogenic properties. Phytoestrogens appear to exert their physiological effects through a variety of possible mechanisms, such as their ability to bind to estrogen receptors and their actions on tyrosine kinases and growth factors. Phytoestrogens can be classified into three main categories consisting of isoflavones, lignans, and coumestans. A variety of commonly consumed foods contains appreciable amounts of these plant compounds which have been identified in various human body fluids, such as plasma, urine, bile, saliva, feces, breast milk, prostatic fluid and semen. Accumulating evidence from both clinical and epidemiological studies has suggested that dietary estrogens may potentially affect the human endocrine system. The existing evidence reviewed here will identify the current research in this area, which will include both the possible beneficial and adverse effects which dietary estrogens may have on the human endocrine system as it relates to breast, prostate and colon cancer, endogenous hormones, the menstrual cycle, menopausal symptoms, coronary heart disease, and osteoporosis. Moreover, the issue of infants fed soy-based formulas will be addressed.