Effects of soy products in reducing risk of spontaneous and neutron-induced liver-tumors in mice.

In the Orient people including the Japanese, have traditionally consumed products of fermented soy bean such as miso or soy sauce or sake in their daily life as part of a meal or as a flavor. However, there have been almost no scientific evaluation of their biological effect for human health up to now. This study was designed to examine whether occurrence of spontaneous or radiation induced liver tumors in mice could be influenced by the administration of miso or soy sauce in daily diet. Either intact male C3H/HeN or neutron irradiated B6C3F1 mice of both sexes were fed with 10% miso or 10% soy sauce containing diet for 13 months. In male C3H/HeN mice, both miso and soy sauce diets significantly reduced the frequency and the multiplicity of liver tumors. In neutron irradiated B6C3F1 mice, feeding miso diet significantly decreased the frequency and multiplicity of liver tumors in the male, but not in the female mice. Although there have already been reports of anti-mutagenic or anti-tumorigenic effect of soy bean products, inhibitory effects of dietary miso or soy sauce for mouse liver tumorigenesis obtained in the present study may be caused by multi-factorial mechanisms such as accommodation of immunologic or hormonal status in the body.