ABSTRACT
Cancer has become one of the major health problems around the world. In the U.S., about 1,372,910 new cases of cancer will be diagnosed and 570,280 people will die from cancer in 2005.1 Although cancer occurs in every country around the world, there are wide geographic variations in the incidence of cancer. The incidences of hormone-related cancers including breast, prostate, endometrium,
and ovary cancers are much higher in the U.S. and European countries compared to Asian countries such as Japan and China. It has been believed that the difference in the incidences is due to the environmental and lifestyle factors including dietary habits. The Japanese and the Chinese consume a traditional diet high in soy products. Dietary intakes of 39.4 and 47.4 mg soy isoflavone/day in Chinese and Japanese populations, respectively, have been reported, whereas the dietary consumption of soy isoflavones is less than 1 mg/day in the general population in the U.S.2-4 Epidemiological studies have revealed that high consumption of soybean is inversely associated with the risk of hormone-related cancers.5-7 Therefore, isoflavones that mainly exist in soybean have received much attention as dietary factors having inhibitory effects on carcinogenesis. In recent years, growing evidence from animal and in vitro studies has demonstrated that isoflavones are able to exert their inhibitory effects on the development of cancers, cancer cell growth, and cancer progression, suggesting that isoflavones may be promising agents for cancer prevention and/or treatment.
