ARTICLES Randomized Trial of Intake of Fat, Fiber, and Beta Carotene to Prevent Colorectal Adenomas

the high intake of fat and low intake of dietary Tiber, beta carotene, and other dietary constituents and the risk of colorectal neoplasia has been inconsistent and has not provided a sufficient basis for recommendations concerning the dietary prevention of large-bowel cancer in humans. Purpose: We conducted a clinical trial to assess the effects on the incidence of adenomas of reducing dietary fat to 25 % of total calories and supplementing the diet with 25 g of wheat bran daily and a capsule of beta carotene (20 mg daily). Methods: We performed a randomized, partially double-blinded, placebo-controlled factorial trial in which half the patients were assigned to each intervention, resulting in seven intervention groups and one control group. Eligibility criteria included histologic confirmation of at least one colorectal adenoma and confidence expressed by the colonoscopist that all polyps had been removed. Dietary changes were individually initiated and monitored by dietitians and research nurses. At surveillance colonoscopy, the size and location of all polyps were recorded, and their histology was later centrally reviewed. Among 424 patients who were randomly assigned in the trial, 13 were found to be ineligible upon histologic review. Among the remaining 411, complete outcome data were collected from 390 at 24 months and from 306 at 48 months. All P values are from two-sided tests of statistical significance. Results: There was no statistically significant prevention of total new adenomas with any of the interventions. We found a statistically non-significant reduced risk of large adenomas (>10 mm) with the low-fat intervention: At 24 months, the odds ratio (OR) adjusted for potential confounders = 0.4 and 95 % con-fidence interval (CI) = 0.1-1.1; at 48 months, OR = 0.3 and 95 % CI = 0.1-1.0. Less and statistically nonsignificant reduc-tions in the risk of large adenomas were found with whea