There is increasing evidence in favour of a link between diets high in soyabeans, a rich source of the isoflavones genistein and daidzein, and reduced incidence of colon cancer and hormone-dependent cancers, such as breast and prostate cancer (for review, see Bingham et al. 1998). A number of studies in animal models demonstrate a chemopreventive effect of soyabean and/or genistein. For example...