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 clinical trial designed to determine the effects of a high-fiber (4.30 g/MJ), high-fruit-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 could 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 past 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 assessment instruments were used to measure dietary change: food-frequency questionnaires (in 100% of the sample), 4-d food records (in a 20% random cohort), and 24-h dietary recalls (in a 10% random sample). RESULTS: Intervention participants made and sustained significant changes in all PPT goals as measured by the dietary assessment instruments; the control participants' intakes remained essentially the same throughout the trial. The absolute differences between the intervention and control groups over 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 vegetables/MJ (95% CI: 0.25, 0.29). Intervention participants also reported significant changes in the intake of other nutrients and food groups. The intervention group also had significantly higher serum carotenoid concentrations 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.

Self-rated quality of life measures: effect of change to a low-fat, high-fiber, fruit and vegetable enriched diet.

The Polyp Prevention Trial (PPT) was a multicenter, randomized clinical trial to determine the effect of a low-fat (20% of energy from fat), high-fiber (18 g/1,000 kcal/day), high-fruit/vegetable (3.5 servings/1,000 kcal/day) eatingplan on the recurrence of large bowel adenomatous polyps. The PPT provided an opportunity to examine the impact of dietary changes on quality of life. At baseline and annuallyfor 4 years, participants in the Quality of Life Substudy of PPT completed a Quality of Life Factors (QF) Questionnaire, a modified Block-National Cancer Institute Food Frequency Questionnaire, and a Health and Lifestyle Questionnaire. The 51-item QF Questionnaire assessed changes in nine domains: taste, convenience, cost, self-care, social, health assessment, health belief health action, and life satisfaction. The analysis compared annual changes in domain scores for intervention (n = 194) and control (n = 200) participants. At Year 1, 363 (92%) completed a questionnaire, and 325 (82%) participants completed a Year 4 questionnaire. There were no statistically significant differences between treatment groups in the change from baseline to Year 1 for the convenience, cost, taste, health assessment, and life satisfaction domains. At Year 1, intervention participants rated the self-care (p < .001), health belief (p = .021), and health action (p < .001) domains significantly higher and the social domain significantly lower (p <.001) than control participants. These changes were consistent through Years 2, 3, and 4. This study

Measuring cell proliferation in the rectal mucosa. comparing bromodeoxyuridine (BrdU) and proliferating cell nuclear antigen (PCNA) assays.

Cell proliferation in the human colorectum can be measured using bromodeoxyuridine (BrdU) or proliferating cell nuclear antigen (PCNA) assays. Using data from the National Cancer Institute's Polyp Prevention Trial, these two assays are compared using correlation coefficients and variance components analysis. Adjusting for fixed as well as for the random effects of between-biopsy and scoring variation, the estimated correlation is 0.46 for the log labeling index and 0.45 for log proliferative height. This is an estimate of the highest correlation that can be achieved by taking multiple biopsies scored by multiple scorers. For single biopsies, the estimated correlation is 0.16 and 0.10, respectively. There are significant differences between the variance components for the two assays. For example, for log labeling index, PCNA has a lower variation between biopsies than BrdU, but higher variation between scorings. When used in a clinical or epidemiological setting, it is important to take multiple biopsies at multiple time points.

An evaluation of rectal mucosal proliferation measure variability sources in the polyp prevention trial: can we detect informative differences among individuals' proliferation measures amid the noise?

We assessed components of total variability of bromodeoxyuridine (BrdUrd) and proliferating cell nuclear antigen (PCNA) assays of rectal mucosal proliferation in a subset of 390 participants from the U. S. National Cancer Institute's multicenter Polyp Prevention Trial. Biopsies were blindly double-scored by two technicians. For those participants for whom at least one evaluable biopsy was obtained, a mean of 2.0 and 2.6 biopsies, and 6.2 and 8.7 crypts/biopsy were evaluated, respectively, with the BrdUrd and PCNA assays. Factors such as clinical center, scorer, and month of biopsy collection significantly affected the observed values of the labeling index (LI) and proliferative height (PH). Therefore, it is essential to control or adjust for these variables in proliferation studies. Sources of random variation for LI and PH measures remaining after the aforementioned factors include between-participant variation and several sources of within-participant variation, including variation over time, between biopsies, and between multiple measurements on the same biopsy. Both LI and PH measurements exhibited substantial variability over time, between biopsies, and from reading-to-reading of the same biopsy. When other sources of variability have been accounted for, the PCNA LI seems to have little between-participant variation. This brings into question its utility as a marker in colorectal cancer studies. The PCNA PH showed significant between-participant variability and may hold some promise as a useful marker in colorectal cancer studies. Results for BrdUrd were less conclusive. The BrdUrd LI showed marginally significant between-participant variation, whereas the corresponding variation for PH was nonsignificant.

Fat-gram counting and food-record rating are equally effective for evaluating food records in reduced-fat diets.

OBJECTIVE: To compare rates of adherence to low-fat diets using food-record rating and fat-gram counting, to evaluate dietary adherence using the fat-gram counting method, and to assess correlations between food-record rating and fat-gram counting. DESIGN: A diet monitoring and observation study was conducted to compare the effectiveness of food-record rating and fat-gram counting to evaluate dietary adherence. Subjects were randomly assigned to the food-record rating group of the fat-gram counting group. Each participant was asked to complete four 3-day food records. Food records were evaluated by food-record rating for one group and by fat-gram counting for the other. Each record was then scored using the alternate system. For a subset, manually calculated fat-gram values were compared for accuracy with values from the Nutrient Data Systems database. STATISTICAL ANALYSES PERFORMED: Mantel-Haenszel chi 2, regression, and K analyses were used to evaluate adherence rates and within-subject agreement between fat-gram counting and food-record rating. SUBJECTS/SETTING: Seventy-eight participants were recruited from a lipid-lowering research trial conducted in Houston, Tex. RESULTS: Strong correlations were found between fat-gram values calculated manually and those calculated using the Nutrient Data Systems. No significant differences in adherence rates were found between the food-record rating and fat-gram counting groups. CONCLUSIONS: Fat-gram counting is at least as effective as food-record rating in monitoring dietary fat content. Dietitians can use it as an alternative dietary fat-monitoring procedure for clinical practice and research.

The polyp prevention trial II: dietary intervention program and participant baseline dietary characteristics.

The Polyp Prevention Trial (PPT) is a multicenter randomized controlled trial to evaluate whether a low-fat, high-dietary fiber, high-fruit and -vegetable eating pattern will reduce the recurrence of adenomatous polyps of the large bowel. Men and women who had one or more adenomas removed recently were randomized into either the intervention (n = 1037) or control (n = 1042) arms. Food frequency questionnaire data indicate that PPT participants at the beginning of the trial consumed 36.8% of total energy from fat, 9.7 g of dietary fiber/1000 kcal, and 3.8 daily servings of fruits and vegetables. Baseline dietary characteristics, including intake of fat, fiber, and fruits and vegetables, as well as other macro- and micronutrients, were similar in the two study groups. The intervention participants receive extensive dietary and behavioral counseling to achieve the PPT dietary goals of 20% of total energy from fat, 18 g/1000 kcal of dietary fiber, and 5-8 daily servings (depending on total caloric intake) of fruits and vegetables. Control participants do not receive such counseling and are expected to continue their usual intake. Dietary intake in both groups is mentioned annually using a 4-day food record (also completed at 6 months by intervention participants only) and a food frequency questionnaire, with a 10% random sample of participants completing an annual unscheduled 24-h telephone recall. Blood specimens are drawn and analyzed annually for lipids and carotenoids. This article provides details on the rationale and design of the PPT dietary intervention program and describes the participant baseline dietary intake data characteristics.