[Dietary mutagenicity and stomach cancer epidemiology]

On the comparison of stomach cancer mortality between Akita and Iwate prefectures which locate neighboring in northern Japanese mainland shows marked difference, the former very high and the latter very low. Dietary mutagenicity of inhabitants in the two areas were assayed by Rec-assay using B. subtilis and by Ames test using Salmonella TA 100 and TA 98. Both of the results showed the frequencies of positive mutagenicity were significantly higher in Akita than in Iwate. The food composition of the diets tested was compared among the three groups of mutagen-positive, -probable and -negative diets. The positive diet was significantly frequent in broiled meat, grilled fish, salted fish intestine, cooked beans, fried bean curd, sautéed vegetables, salted bracken and sautéed onions. On the other hand, the mutagen-negative diet was significantly frequent in fresh vegetables, cooked potatoes, cooked carrots, milk, bean curd, devils' tongue and confections. The former was called the mutagen-positive food group and the latter the mutagen-negative food group. The mutagenicity tests of each food which belongs to both the groups revealed that the combination of the mutagenic factors and the mutagen-depressive factors in the above mentioned cooked foods caused the variety of mutagenicity of the diet of the inhabitants. A method to evaluate the mutagenic pattern of diet was developed.