CAMBRIDGE, England—Intake of dietary fiber was inversely associated with colorectal cancer risk in a recent English study published in the Journal of the National Cancer Institute (April 20, 2010). Researchers conducted a prospective case–control study nested within seven UK cohort studies, which included 579 case patients who developed incident colorectal cancer and 1996 matched control subjects. They used standardized dietary data obtained from four- to seven-day food diaries that were completed by all participants to calculate the odds ratios for colorectal, colon and rectal cancers with the use of conditional logistic regression models that adjusted for relevant covariates. The odds ratios for colorectal cancer by using dietary data obtained from food-frequency questionnaires that were completed by most participants was also obtained. All statistical tests were two-sided.
Intakes of absolute fiber and of fiber intake density were statistically significantly inversely associated with the risks of colorectal and colon cancers in both age-adjusted models and multivariable models that adjusted for age; anthropomorphic and socioeconomic factors; and dietary intakes of folate, alcohol and energy. For example, the multivariable-adjusted odds ratio of colorectal cancer for highest versus the lowest quintile of fiber intake density was 0.66. However, no statistically significant association was observed when the same analysis was conducted using dietary data obtained by food-frequency questionnaire. Researchers noted, “Methodological differences (i.e., study design, dietary assessment instruments, definition of fiber) may account for the lack of convincing evidence for the inverse association between fiber intake and colorectal cancer risk in some previous studies.”
