Human feeding studies are one of many techniques used to develop and test diet-disease hypotheses (1,2). Such studies employ numerous methodologies for meal delivery. The study design and feeding method must be carefully considered to minimize labor intensity and cost while maximizing dietary control and participant adherence. The desired outcome is valid scientific data collection.
Until recently, investigators believed that feeding studies could be conducted only when participants were confined to an inpatient unit, where adherence could be monitored continuously. The high cost of staffing an inpatient unit and the need to rely on a few people who were willing to spend extended periods away from home prompted investigators to devote time and resources to the development of outpatient studies as practical alternatives. Although outpatient feeding studies generally are less expensive to conduct and provide less disruption to participants' daily lives than inpatient studies, they are frequently more difficult to implement, because participant motivation and adherence become central issues. In addition, outpatient feeding studies are more labor-intensive for the research kitchen staff, because meals must be packed safely for transport, storage, and convenient reheating.
For these reasons, designing and selecting menus that promote participant adherence to the diet and that efficiently utilize the research kitchen staff and resources are important for conducting well-controlled outpatient feeding studies. Additionally, studies involving multiple feeding sites require well-documented and standardized procedures that can be [TABULAR DATA FOR TABLE 1 OMITTED] duplicated at several sites (3). Standardization limits diet discrepancies, thus ensuring that participants from different centers are receiving the same diets and allowing data from all sites to be pooled for analysis.
One of the first multicenter outpatient controlled feeding studies that employed common dietary procedures was the 4-year Dietary Approaches to Stop Hypertension (DASH) trial (4,5). DASH was a 4-center, randomized clinical trial designed to compare the effects of 3 dietary patterns on blood pressure among participants with diastolic blood pressures of 80 to 95 mm Hg and systolic blood pressures of less than 160 mm Hg. The dietary patterns varied the content of minerals (potassium, calcium, and magnesium), macronutrients (total fat, saturated fat, and protein), cholesterol and fiber. Sodium was held constant. For 11 weeks, participants were provided all their food. They were required to eat 1 meal each weekday at the feeding site and were given the remainder of their food to consume at home or work. Over 2 years, each site enrolled 5 cohorts of 10 to 37 participants for a total of 459 subjects.
The DASH Diet Subcommittee - a team of dietitians from 4 feeding sites, a coordinating center, and the National Heart, Lung, and Blood Institute, Bethesda, Md - was challenged to design study menus and to develop suitable food production and distribution guidelines. Expanding on their experience with single-center feeding studies, subcommittee members developed and selected 3 sets of 7-day cycle menus matching the 3 diet arms of the study protocol. The purpose of this article is to describe factors considered and procedures followed in the design and selection of menus for the DASH study, a process applicable to all well-controlled feeding studies. The major tasks were to define methodologies to guide menu design and food production; to select a nutrient database and calculate the …