Dietary change in an intervention trial of wheat bran fiber and colorectal adenoma recurrence.

Purpose: The objectives of this study were to determine whether participants in the Wheat Bran Fiber (WBF) trial exhibited changes in diet over time, and whether these changes were differential by assigned treatment group.

Methods: The WBF trial was a randomized trial with participants assigned to one of two groups: a low-fiber (2.0 g/d) or high-fiber (13.5 g/d) wheat bran fiber cereal supplement. A total of 685 participants from both treatment groups completed the Arizona Food Frequency Questionnaire (AFFQ) at baseline, year one, and year three of the trial. Means were calculated for nutrient intake, change in nutrient intake, number of food group servings, and change in number of food group servings.

Results: For both treatment groups combined, significant increases were observed for most micronutrients and vitamins at years one and three, while fat intake significantly decreased. Participants from both groups significantly increased their consumption of cereals, breads, and crackers, but decreased the number of servings from the meat, poultry, and egg group, the fats group, and the salty snacks group. The only differential changes in intake between the treatment groups were for sugar and iron, which increased to a lesser extent among those assigned to the high-fiber treatment as compared with the low-fiber group.

Conclusions: Although differential dietary intake was not appreciable in the WBF trial, participants exhibited longitudinal changes. Future intervention studies should carefully monitor dietary changes during the trial with multiple dietary assessment tools to assess potential secular and treatment-related diet changes.