Ito et al. (20) examined the suppressive effects of diets
containing soy sauce or miso (fermented soybean paste) on
spontaneous liver tumors in male C3H mice. Diets containing
10% soy sauce or 10% miso were fed to the mice for 13
months. In this long-term feeding experiment, both miso
and soy sauce significantly reduce the frequency and multiplicity
of liver tumors in mice (Table 3). They presumed
that the estrogenic effect of isoflavone may be a causative
factor for tumor prevention in the case of the mouse liver.
However, soy sauce does not contain high amounts of water
insoluble isoflavones, because isoflavones, such as genistin