Health Effects and Safety of Soy and Isoflavones

Isoflavones found in soybeans are nonsteroidal phytoestrogenic and antioxidative diphenolic compounds with potential roles in the prevention of chronic diseases, including hormone dependent cancer cardiovascular diseases, osteoporosis, and postmenopausal syndrome. Japanese consume 40–100 mg/day from various kind of soy foods, and it may contribute to the low incidence of above diseases. S(–)-equol, a metabolite of daidzein by the intestinal microflora, shows the strongest estrogenic activity among isoflavones. Epidemiology, metabolism and measurements, animal and in vitro experiments, randomized clinical study and metaanalysis, supplements, and safety are reviewed.