Isoflavones levels in Japanese men and womenEpidemiological studies show that Asians have much lower incidences of prostate and breast cancer than Western people. Because Asians eat more soy foods many scientists believe that consumption of soy foods, such as tofu, soy milk, tempeh and miso, has a protective effect against these types of cancer. But do Asians really eat that much soy foods? Soy foods are a rich source of isoflavones, so determining serum levels of isoflavones will give a good indication of soy food intake.
Only individuals older than 40 years, who more likely to consume a traditional Japanese diet, were considered in this study. Unfortunately, the Japanese are slowly abandoning their traditional soy-rich diet in favour of more Westernized foods. This may explain the recent increase in incidence of prostate and breast cancer in Japan.
Source: Phytoestrogen concentrations in serum from Japanese men and women over forty years of age. Journal of Nutrition. 2002 Oct;132(10):3168-71.