Implementation of a 4-y, high-fiber, high-fruit-and-vegetable, low-fat dietary intervention: results of dietary changes in the Polyp Prevention Trial

Background: The Polyp Prevention Trial (PPT) was a multicenter randomized c linical trial designed to determine the effects of a high-fiber (4.30 g/MJ) , high-ftuit-and-vegetable (0.84 servings/MJ), low-fat (20% of energy from fat) diet on the recurrence of adenomatous polyps in the large bowel. Objective: Our goal was to determine whether the PPT intervention plan coul d effect change in 3 dietary goals and to examine the intervention's effect on the intake of other food groups and nutrients. Design: Participants with large-bowel adenomatous polyps diagnosed in the p ast 6 mo were randomly assigned to either the intervention (n=1037) or the control (n=1042) group and remained in the trial for 4 y. Three dietary ass essment instruments were used to measure dietary change: food-frequency que stionnaires (in 100% of the sample), 4-d food records (in a 20% random coho rt), and 24-h dietary recalls (in a 10% random sample). Results: Intervention participants made and sustained significant changes i n all PPT goals as measured by the dietary assessment instruments; the cont rol participants' intakes remained essentially the same throughout the tria l. The absolute differences between the intervention and control groups ove r the 4-y period were 9.7% of energy from fat (95% CI: 9.0%, 10.3%), 1.65 g dietary fiber/MJ (95% CI: 1.53, 1.74), and 0.27 servings of fruit and vege tables/MJ (95% CI: 0.25, 0.29). Intervention participants also reported sig nificant changes in the intake of other nutrients and food groups. The inte rvention group also had significantly higher serum carotenoid concentration s and lower body weights than did the control group. Conclusion: Motivated, free-living individuals, given appropriate support, can make and sustain major dietary changes over a 4-y period.