Phytoestrogens: effects on the reproductive system

Phytoestrogens are ubiquitous compounds in nature. They are found largely in soy but are also abundant in legumes and vegetables. They include a wide variety of chemicals with diverse estrogenic and antiestrogenic activities. Different phytoestrogens have different mechanisms of action based on estrogen receptor subtypes, endogenous estrogen concentrations, and cellular genetic make-up. Effects of phytoestrogens on the reproductive system have been known for decades based on several in vitro and animal studies. Their roles in humans remain unclear. Several beneficial health effects in adults have been associated with phytoestrogens, such as a protective role against the development of breast and prostate cancers. Evidence to support this comes from epidemiologic studies revealing lower incidences of breast and prostate cancers in Asian populations consuming a phytoestrogen rich diet. The effect of phytoestrogens on the menstrual cycle and endogenous sex hormones levels in premenopausal and postmenopausal women remains controversial because of conflicting results from several human studies. Most recently, concern has been raised about a possible effect on growth and sexual development in infants consuming soy formulas because of their high phyto, estrogen content; high plasma phytoestrogen levels were found in these infants. Limited studies have not demonstrated adverse effects related to soy formula ingestion in children. However, the develops mental effects of these compounds have not been carefully evaluated and deserve further studies.