Stomach cancer in Japan.
A study of 783 patients with stomach cancer and 1,566 hospital controls in Hiroshima and Miyagi prefectures of Japan showed that farmers, representing mostly the lowest socioeconomic class, had higher risk of developing stomach cancer. The usual inverse gradient in risk by social class was in the urban population of Miyagi, but not Hiroshima, prefecture. The study in Japan did not reproduce the association of stomach cancer with consumption of salted/dried fish and salt-pickled vegetables described for the Hawaiian Japanese. Salted/dried fish and pickled vegetables were more widely used by farmers than by nonfarmers in Japan or by Japanese migrants to Hawaii. The ability to detect associations for these typical Japanese foods in Hawaii stemmed from the fact that these reduced levels of use were more completely expressed by the Hawaiian-Japanese controls than by patients. The lower risk of developing stomach cancer for lettuce and celery users agreed with the Hawaiian-Japanese findings, and the combined results supported conjectures on possible protective food effects. Lettuce, in particular, warranted attention from this viewpoint, since similar findings have been consistently reported.