Fat, fiber, meat and the risk of colorectal adenomas.

OBJECTIVE: The aim of this study was to determine the relationship between fat, fiber, and meat intake, and risk of colorectal adenoma recurrence.
METHODS: We determined adenoma recurrence and dietary intake for 1,520 participants in two randomized trials: The Antioxidant Polyp Prevention Study and Calcium Polyp Prevention Study. Subjects underwent baseline colonoscopy with removal of all adenomas, and dietary intake was estimated with a validated semiquantitative food frequency questionnaire. Follow-up colonoscopy was performed 1 and 4 yr later. Pooled risk ratios for adenoma recurrence were obtained by generalized linear regression, with adjustment for age, sex, clinical center, treatment category, study, and duration of observation.
RESULTS: In the total colorectum, fiber intake was weakly and nonsignificantly associated with a risk for all adenomas (RR quartile 4 vs quartile 1=0.85, 95% CI 0.69-1.05) and advanced adenomas (RR=0.88, 95% CI 0.54-1.44). Associations were stronger for adenomas in the proximal colon (RR=0.73, 95% CI 0.56-0.97) and some fiber subtypes (fruit and vegetable, grain). There was no association between fat or total red meat intake and risk of adenoma or advanced adenoma recurrence. However, when considering other meats, risk (quartile 4 vs quartile 1) for advanced adenoma was increased for processed meat (RR=1.75, 95% CI 1.02-2.99) and decreased for chicken (RR=0.61, 95% CI 0.38-0.98).
CONCLUSION: The inverse associations between fiber intake and risk of adenoma recurrence we observed are weak, and not statistically significant. Our data indicate that intake of specific meats may have different effects on risk.