Review Soy Isoflavones and Soyasaponins: Characteristics and Physiological Functions

Soy is an important food in Asia and many studies have suggested that the low incidences of chronic diseases in Asian countries are associated with diets that are rich in soy. Soy contains many kinds of phytochemicals, and soy isoflavones and soyasaponins have received considerable attention. Twelve isoflavone components have been isolated from soy: three aglycones (daidzein, genistein, and glycitein), and their respective nine glucosidic conjugates. Soy isoflavones are similar in structure to estrogen and exhibit both estrogenic and antiestrogenic activities. Soy isoflavones exhibit anticancer activity, can reduce the risk of cardiovascular disease, and are beneficial to brain and bone health. Soyasaponins are divided into three groups (A, B, and E saponins), and they exhibit hypocholesterolemic, anticancer, hepatoprotective, antioxidative, and anti-human-immunodeficiency-virus effects. Despite the abundant literature suggesting that soy isoflavones and soyasaponins have potential applications in preventive medicine, further research is needed to standardize dosages and ensure their efficacy. Key words: soy, chronic diseases, phytochemicals, isoflavones, soyasaponins, preventive medicine For more than 1,000 years, Asian people have been consuming soy in a variety of traditional soy food products. In contrast, soy has become a significant food in Western countries only within the past 20 years, and still plays a minor dietary role despite a good source of protein, dietary fiber, and a variety of phytochemicals. Soy contains numerous phytochemicals including isoflavones, phytic acid, phytosterols and saponin