Background: Colorectal cancer (CRC) is a leading cause of cancer death in the United States. Most cases of CRC arise in adenomatous polyps. It has been estimated that 25%-35% of colon adenoma risk could be avoidable by modification of dietary and life-style habits.
Methods: We estimated the association between total dietary fiber and fiber intake from fruits, vegetables, and grains, and the risk of physician-diagnosed colon polyps among 2818 men and women who had undergone colonoscopy. Data were drawn from 2 cohort studies-the Adventist Health Study-1 (AHS-1) of 1976 and the Adventist Health Study-2 (AHS-2) conducted from 2002 to 2005. Dietary information was obtained from the self-administered questionnaire from AHS-1, while outcome was assessed from AHS-2 data. Multivariate logistic regression analysis was used to estimate the period risk of incident cases of polyps.
Results: A total of 441 incident cases of colon polyps were identified. After adjusting for age, sex, body mass index, physical activity, education, and alcohol and meat consumption, total fiber intake was inversely associated with the risk of colon polyps (odds ratio [OR] for highest vs lowest quartile = 0.71, 95% confidence interval [CI] 0.51-0.99). This association showed a dose-response effect (p = .04). Analyses of various sources of fiber showed the most clear effect of fiber from vegetables including legumes (OR for highest vs lowest quartile = 0.65; 95% CI 0.47-0.90; p = .02).
Conclusions: In this population comprising a high proportion of vegetarians, persons who consumed low amounts of fiber, especially fiber contained in vegetables, had a higher risk of developing colon polyps.