Dietary patterns and colorectal cancer risk in Japan: the Ohsaki Cohort Study.

PURPOSE
To evaluate dietary patterns in relation to colorectal cancer risk in Japanese.

METHODS
We prospectively assessed the association between dietary patterns among the Japanese and the risk of colorectal cancer. Dietary information was collected from 44,097 Japanese men and women aged 40-79 years without a history of cancer at the baseline in 1994.

RESULTS
During 11 years of follow-up, we documented 854 cases of colorectal cancer, which included 554 cases of colon cancer and 323 cases of rectal cancer. Factor analysis (principal component analysis) based on a validated food frequency questionnaire identified three dietary patterns: (1) a Japanese dietary pattern, (2) an "animal food" dietary pattern, and (3) a high-dairy, high-fruit-and-vegetable, low-alcohol (DFA) dietary pattern. After adjustment for potential confounders, the DFA pattern was inversely associated with the risk of colorectal cancer (hazard ratio of the highest quartile vs the lowest, 0.76; 95 % confidence interval 0.60-0.97; p for trend = 0.02). When colon and rectal cancers were separated, the inverse association between the DFA pattern and cancer risk was observed for rectal cancer (p for trend = 0.003), but not for colon cancer (p for trend = 0.43). No apparent association was observed for either the Japanese dietary pattern or the "animal food" dietary pattern.

CONCLUSIONS
The DFA dietary pattern was found to be inversely associated with the risk of colorectal cancer. This association was observed for rectal cancer, but not for colon cancer.