Precision of the doubly labeled water method in a large-scale application: evaluation of a streamlined-dosing protocol in the Observing Protein and Energy Nutrition (OPEN) study.

OBJECTIVE: To evaluate whether the doubly labeled water (DLW) method is precise under conditions required for a large-scale evaluation of dietary intake instruments. DESIGN: Energy expenditure was measured in 484 subjects (main study). Subjects received one of five different weight DLW dose bottles prepared in advance of the study. A repeat energy expenditure measure was obtained in a subset of 24 subjects (substudy). DLW measures of energy expenditure were performed over a 2-week interval with urine collection at the beginning and end. SETTING: Free-living environment with three clinic visits in the Maryland suburban area of Washington, DC. SUBJECTS: A total of 484 subjects (261 men and 223 women) aged 40-69 y, 24 of whom (13 men and 11 women) participated in a substudy in which DLW was administered a second time. RESULTS: The coefficient of variation of the DLW energy expenditure measurement was 5.1%. This included a 2.9% analytical and a 4.2% physiologic variation. Based on observed initial isotopic enrichment, the preweighed dosages were optimal in 70% of the main study subjects, and 9% received a dose that was less than optimal. Only six subjects (1%) were excluded because the final isotopic enrichment was too low to conduct precise measurement. CONCLUSIONS: Use of preweighed DLW dosages did not compromise the precision of the DLW method. The DLW method is a reliable measure of energy expenditure for large-scale evaluations of dietary intake instruments.

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

Reliability and validity of the 24-hour recall.

The reliability and validity of the 24-hour dietary recall method was tested statistically by comparing observed with recalled intakes of kilocalories and protein. Data on observed intake of 28 children, aged 10 through 12, with asthma, cystic fibrosis, or diabetes, participating in a summer camp program, were obtained by unobtrusive observation. The same subjects were interviewed within 24 hours after the observation. Intakes of kilocalories and of protein were computed for both observed and recalled data. The two sets of data were compared by paired t-test and regression analysis. A large and significant difference was found between mean recalled and mean observed intakes for both kilocalories and protein. This coupled with a low but significant coefficient for reliability limits the usefulness of this dietary assessment tool in the age group studied.