Soy and Soy Products, Isoflavones, Equol, and Health

Abstract

In Asian countries, soybeans have been used as food and food ingredients for centuries and their consumption have been associated with beneficial health effects. In addition to their nutritive value, soybeans have many active chemical compounds, among which isoflavones are the most important. Isoflavones are plant-derived phytoestrogens, chemically comparable in their structure and properties to human estrogens. For isoflavones to become bioavailable, their activation and/or conversion into more active metabolites, such equol from daidzein, must occur. Equol is the isoflavone metabolite with the greatest estrogenic activity and antioxidant capacity. Epidemiological studies have suggested that high intakes of isoflavones reduce the symptoms of menopause as well as the incidence of hormone-dependent and aging-associated diseases such as osteoporosis, cardiovascular disease and cancer. This chapter reviews soy consumption, isoflavone metabolism, and briefly summarizes the results of recent clinical trials on, and meta-analyses of, the effects of isoflavone consumption on human health.