Soy, soy isoflavones and breast cancer risk

In recent years there has been considerable investigation about the potentials of soyfoods to reduce the risk of cancer, particularly breast cancer. Isoflavones are compounds with a chemical structure similar to estrogen and can bind to estrogen receptor. The relationship between soyfoods and breast cancer has become a controversial issue because of concerns -based mostly on some in vitro and rodent data- that isoflavones may stimulate the growth of existing estrogen-sensitive breast tumors. However; some have indicated that soy isoflavones have antitumor and antiproliferative effects. The epidemiologic data are generally consistent with the animal studies, showing no increased risk. In limited clinical studies there is no evidence that isoflavone intake increases tumor growth or proliferation of carcinoma cells. Also, epidemiological studies on breast cancer survival showed that soy isoflavones decrease recurrence and mortality of disease. Furthermore, it is demonstrated that in healthy women the pharmacologic dose of estrogen has very low if any risk for breast cancer. Because of the increasing popularity of soyfoods and the commercial availability of isoflavone supplements and existing concern regarding the estrogen-like effects of isoflavones in the breast, more clinical research seems to be necessary.