Descriptive characteristics of the dietary patterns used in the Dietary Approaches to Stop Hypertension Trial. DASH Collaborative Research Group.

The Dietary Approaches to Stop Hypertension trial was a randomized, multicenter, controlled feeding study to compare the effect on blood pressure of 3 dietary patterns: control, fruits and vegetables, and combination diets. The patterns differed in selected nutrients hypothesized to alter blood pressure. This article examines the food-group structure and nutrient composition of the study diets and reports participant nutrient consumption during intervention. Participants consumed the control dietary pattern during a 3-week run-in period. They were then randomized either to continue on the control diet or to change to the fruits and vegetables or the combination diet for 8 weeks. Sodium intake and body weight were constant during the entire feeding period. Analysis of variance models compared the nutrient content of the 3 diets. Targeting a few nutrients thought to influence blood pressure resulted in diets that were profoundly different in their food-group and nutrient composition. The control and fruits and vegetables diets contained more oils, table fats, salad dressings, and red meats and were higher in saturated fat, total fat, and cholesterol than was the combination diet. The fruits and vegetables and combination diets contained relatively more servings of fruits, juices, vegetables, and nuts/seeds, and were higher in magnesium, potassium, and fiber than was the control diet. Both the fruits and vegetables and combination diets were low in sweets and sugar-containing drinks. The combination diet contained a greater variety of fruits, and its high calcium content was obtained by increasing low-fat dairy products. In addition, the distinct food grouping pattern across the 3 diets resulted in substantial differences in the levels of vitamins A, C, E, folate, B-6, and zinc.

The Linear Index Model for establishing nutrient goals in the Dietary Approaches to Stop Hypertension trial. DASH Collaborative Research Group.

Establishing target levels of nutrients in feeding studies presents a challenge to dietitians. Although researchers studying energy-containing nutrients, such as protein and fat, commonly establish target levels according to body weight or as a percentage of energy, it is less clear how to establish levels of micronutrients. Typically, a constant target level is used regardless of energy requirements. Alternatively, nutrients could be provided at a fixed level per 1,000 kcal. Such an approach, however, could result in absolute levels of nutrient intakes that are difficult to achieve through foods alone, particularly for persons with high energy requirements. This report describes the Linear Index Model, a new approach for establishing target levels of selected micronutrients in the Dietary Approaches to Stop Hypertension trial. This model indexes micronutrient levels to energy levels to achieve a linear range of targeted intake in proportion to the energy intake. The Linear Index Model has several benefits: it takes advantage of indexing nutrients according to energy requirements, thus providing levels of nutrient intakes that can be readily achieved by foods; it is based on population consumption data, thus providing a realistic range of intakes for the experimental conditions; and it ensures distinct contrasts in experimental conditions. The Linear Index Model is a feasible and practical approach for establishing target levels of nutrients in feeding studies.

Menu design and selection for multicenter controlled feeding studies: process used in the Dietary Approaches to Stop Hypertension trial. DASH Collaborative Research Group.

Outpatient feeding studies are being used increasingly more often than inpatient studies because they are less expensive to conduct and less disruptive to participants' daily lives. Frequently, however, they are more difficult to implement. Studies involving multiple feeding centers add an additional layer of cooperation, coordination, and standardization to the already complex task of developing and delivering research diets. This was true for the 4-year Dietary Approaches to Stop Hypertension (DASH) trial, one of the first multicenter outpatient controlled feeding studies. This 4-center, randomized clinical trial was designed to compare the effects of 3 dietary patterns on blood pressure. After a year of development, 3 sets of 7-day cycle menus that met the study nutrient criteria and that were appropriate for varying food production routines and staffing patterns at the 4 clinical centers were adopted. The major development tasks were: defining methodologies to guide menu design and food production; selecting a nutrient database and calculating nutrient content of menus; evaluating and selecting the menus; and adjusting the menus for final use. The purpose of this article is to describe the steps and considerations in the design and selection of menus for the DASH trial, a process applicable to all well-controlled feeding studies.

Dietary adherence in the Dietary Approaches to Stop Hypertension trial. DASH Collaborative Research Group.

Participants in controlled feeding studies must consume all study foods and abstain from all other foods. In outpatient studies in which adherence may be compromised by free-living conditions, promoting, documenting, and monitoring dietary adherence are necessary. In the Dietary Approaches to Stop Hypertension (DASH) trial, a thorough participant screening process, an orientation session, and a run-in feeding period before randomization aided in the selection of participants who would most likely adhere to the demands of the study protocol. Throughout the feeding period, various educational and motivational techniques were used to encourage DASH participants to adhere to the dietary protocol. Both objective and subjective methods documented excellent participant adherence. Daily monitoring of individual adherence was based on meal attendance, body weight measurements, and daily diaries. Urinary sodium, potassium, phosphorus, and urea nitrogen values and an anonymous poststudy survey were used to evaluate adherence at the end of the study. Most DASH participants adhered to the feeding regimen by consuming only study foods and no other foods. When adherence lapsed, participants generally cited the lack of menu variety as a reason. Successful participant adherence to the constraints of an outpatient controlled feeding study is possible with carefully selected participants and a variety of adherence-promoting strategies incorporated into the study protocol.

Translating the Dietary Approaches to Stop Hypertension diet from research to practice: dietary and behavior change techniques. DASH Collaborative Research Group.

The Dietary Approaches to Stop Hypertension (DASH) clinical trial demonstrated that a diet that emphasizes fruits, vegetables, and low-fat dairy products, includes whole grains, nuts, fish, and poultry, and is reduced in fats, red meats, sweets, and sugar-containing beverages can be highly effective in lowering blood pressure. The National High Blood Pressure Education Program now suggests the DASH diet for preventing and managing hypertension. For persons modifying their diets, the DASH diet offers varied choices. However, simultaneously modifying several dimensions of a diet can be challenging, even for knowledgeable and motivated persons. Persons who are uncertain about modifying their diet may become overwhelmed by the needed dietary changes. Dietitians and other health care practitioners can help patients adopt the DASH diet by exploring possible ambivalence, increasing motivation, and strengthening commitment to change; encouraging patients to select dietary modifications that will fit their lifestyle; and, finally, offering information about how to change their eating behavior. In this article, we offer dietary advice and counseling suggestions for tailoring interventions to match patients' readiness for adopting the DASH diet.

Utility of produce ratios to track fruit and vegetable consumption in a rural community, church-based 5 A Day intervention project.

Previous research suggests that grocery store characteristics may be useful in evaluating community-based dietary interventions. We undertook a study to determine whether produce ratios (ratios of produce sales to total grocery sales) were a useful indicator of fruit and vegetable (F & V) consumption in a church-based, community intervention trial that promoted 5 A Day guidelines within 10 rural counties of North Carolina. Produce ratios were collected from stores identified by participants in the Black Churches United for Better Health Project. Baseline and study period data for 21 stores in intervention counties and 18 stores in nonintervention counties were compared using repeated-measures analysis of variance. Produce ratios were significantly associated with seasonality (p < 0.0001), but no differences were seen between the two groups of stores. These findings do not support data from individual telephone surveys, which showed significant differences in F & V consumption between participants in the two groups. Our inability to detect differences at the store level may have been due to 1) the incapacity of produce ratios to capture F & V purchases that were juice, frozen, or canned products; 2) shifts in procuring F & Vs from grocery stores to other sources (i.e., gleaning and produce cooperatives); 3) the modest proportion of shoppers that received the full intervention dose; and 4) a general lack of power to detect differences at the store level. Therefore, although produce ratios did not serve as a valid measure for this project, if their limitations are recognized and compensated for, they may have applicability for future investigations that monitor F & V consumption.