Dietary fiber and plant foods in relation to colorectal cancer mortality: The Seven Countries Study

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Abstract
Many observational studies have found that higher consumption of vegetables, and to a lesser extent of fruits, was associated with lower risk of colorectal cancer. In particular, fiber or foods high in fiber have received attention in the potential prevention of colorectal cancer. We performed an ecological analysis with data of the Seven Countries Study, to investigate whether intake of fiber and plant foods contributes to cross-cultural differences in 25-year colorectal-cancer mortality in men. In the Seven Countries Study, around 1960 12,763 men aged 40 to 59 were enrolled in 16 cohorts in 7 countries. Baseline dietary information was gathered in small random samples per cohort, and nutrient intakes were based on chemical analyses of the average diets per cohort. Crude and energy-adjusted mortality-rate ratios were calculated for a change of 10% of the mean intake of fiber and plant foods, i.e., total plant foods, fruits, vegetables, potatoes, grains, and related sub-groups. Fiber intake was inversely associated with colorectal-cancer mortality with an energy-adjusted rate ratio of 0.89 (95% confidence interval 0.80-0.97). An increase of 10 gram of daily intake of fiber was associated with a 33% lower 25-year colorectal-cancer mortality risk. Intakes of vitamin B6 [0.84 (0.71-0.99)] and alpha-tocopherol [0.94 (0.89-0.99)] were also inversely associated with risk. Consumption of plant foods and related sub-groups was not related to colorectal cancer. It appears that fiber intake best indicates the part of plant food consumption, including whole grains, that is relevant for lowering colorectal cancer risk.