Epidemiology of prostate cancer with special reference to the role of diet.

A prospective epidemiologic study of prostate cancer was conducted in Japan. The 10-year follow-up study of 122,261 men aged 40 years and above, who constitute 94.5% of the census population of 29 Health Center Districts, revealed a significantly lower age-standardized death rate for prostate cancer in men who daily ate green and yellow vegetables. This association is consistently observed in each age-group, in each socioeconomic class, and in each prefecture. Selected epidemiologic phenomena, such as the upward trend of the prostate cancer death rate in Japan, intracountry variation of death rate, the significantly lower incidence rate in Japan compared with that of the United States, and elevated risk in Japanese migrants to Hawaii, appear to be explained by the variation in diet and change in amount of green and yellow vegetables ingested. The possible role of vitamin A is considered as a factor in preventing and inhibiting growth of prostate cancer. Most of the other factors studied appear noncontributory, except for marital status; a higher risk was observed in "ever married" men.