Diet Design for a Multicenter Controlled Feeding Trial: The DELTA Program

Objective To describe the process and results of diet standardization, diet validation, and monitoring of diet composition, which were key components of protocol 1 of Dietary Effects on Lipoproteins and Thrombogenic Activity (DELTA-1), the initial protocol in a program of multicenter human feeding studies designed to evaluate the effects of amount and type of fat on lipoproteins and hemostasis parameters in various demographic groups.Design DELTA-1 was based on a randomized, blinded, crossover experimental design. Three diets were fed for 8 weeks to 103 healthy men and women aged 22 to 67 years at 4 field centers. Diet A, an average American diet, was designed to provide 37% of energy from fat, 16% of energy from saturated fatty acids (SFAs); diet B (step 1 diet) was designed to provide 30% of energy from fat, 9% of energy from SFA; and diet C (low SFA diet) was designed to provide 26% of energy from fat, 5% of energy from SFA. Key features of diet standardization included central procurement of fat-containing foods, inclusion of standard ingredients, precision weighing of foods—especially sources of fat and cholesterol—and use of standardized written procedures.Setting For menu validation, a set of 12 menus for each diet was prepared in duplicate and chemically assayed. For monitoring of diet composition during the study, an 8-day diet cycle (6 weekday and 2 weekend menus) was sampled by every field center twice during each of 3 feeding periods.Statistical analyses Means (±standard error) were calculated and compared with target nutrient specifications.Results DELTA-1 was able to provide a standardized diet that met nutrient specifications across 4 field centers over 24 weeks of participant feeding spanning a total of 8 months.Applications Prestudy chemical validation of menus and continuous sampling and assay of diets throughout the study are essential to standardize experimental diets and to ensure that nutrient target goals are met and maintained throughout a controlled multicenter feeding study. J Am Diet Assoc. 1998;98:766–776.     

Development of a Protocol to Assess Dietary Intake Among Hispanics who Have Low Literacy Skills in English

Hispanic adults who had low literacy in English (n=143) and who attended community college English-as-a-Second-Language (ESL) classes, completed 24-hour dietary recalls using version 2.5 of the computerized Minnesota Nutrition Data System (NDS), which included many Hispanic foods. The purposes of our study were to assess the appropriateness of NDS for a Hispanic group who had low literacy in English, to describe the development and implementation of training procedures for NDS interviewers, and to discuss the special problems that occurred using the enhanced version of NDS. Further, nutrient intakes for the study population, as calculated using NDS, were compared with nutrient estimates from the Hispanic Health and Nutrition Examination Survey (HHANES). Results suggest that version 2.5 of NDS is a useful tool for collecting dietary information for Hispanics who have low literacy in English. Challenges encountered during data collection for this study could be categorized into three types: regional differences in foods, food preparation differences, and lack of appropriate options in NDS for preparation methods. Generally, the study group and HHANES participants had similar intakes, although the study group tended to have a more healthful nutrition profile. Overall, findings indicate that NDS is a promising assessment tool for nutrition practitioners who work with Hispanics who have low literacy in English. Continued improvements to the NDS system can correct its shortcomings related to regional/ cultural food differences. J Am Diet Assoc. 1996; 96: 1276-1279.