The Japanese experience suggests that lethal prostate cancer is almost wholly preventable with a quasi-vegan diet, soy products, and green tea

Abstract

In 1950, age-adjusted prostate cancer mortality was 40-fold higher in the US than in Japan. This disparity is not primarily reflective of genetics, as this differential is currently only about 2-fold. The Japanese diet in 1950 was low in protein compared to Western diets, and particularly low in animal protein, a rich source of essential amino acids. Other ecologic epidemiology from 1980 points to prostate cancer mortality being markedly lower in countries with quasi-vegan diets than in those with omnivore diets. Low-protein diets nearly devoid of “high quality” animal protein can be expected to decrease plasma IGF-I, increase plasma levels of adiponectin, and diminish mTORC1 activity – effects that might be expected to lower prostate cancer risk. Hence, the quasi-vegan nature of the Japanese diet ca. 1950 may have contributed importantly to their protection from prostate cancer. But there is reason to suspect that heavy consumption of green tea and regular consumption of soy products rich in isoflavones may have contributed to this protection as well. In any case, it is clearly important to understand why death from what is now the U.S.’s number two cancer killer in males was once extremely rare in Japan.