DASH2 is a multi-center, randomized clinical trial designed to compare the effects of three levels of sodium take and two dietary patterns on blood pressure. This coordinating center application is one of a coordinated set of applications from the five participating institutions. The two dietary patterns are a ~control diet~ that is typical of what Americans generally eat and a ~combination diet~ that is high in fruits, vegetables, fiber and low-fat dairy products and has a reduced total fat, saturated fat, and cholesterol content. The sodium levels range from high (reflecting current US consumption), to medium (reflecting current recommendations), to low (reflecting potentially optimal levels) and vary slightly according to calorie level. Participants are assigned to one of the two dietary patterns using a parallel group design, and are fed at each sodium level using a crossover design. Study participants (n=400) are adults, aged 22 and older, with high normal diastolic blood pressure . Stage 1 (mild) hypertension. Baseline range from 159/95. Half of the participants are African American and half are female. Participants attend a series of three eligibility screening visits followed by a tow-week run-in feeding period and three one-month intervention feeding periods one at each of the three sodium levels. The study provides participants with all of their food during the run-in and intervention feeding periods, although participants resume their normal diets for up to five days between each of the three intervention feeding periods. During the controlled feeding periods participants are required to attend the clinic for at least one meal per day, five days per week, and take home food to eat for their other meals. Clinics deliver the interventions in four successive cohorts, with approximately 25 randomized participants per cohort, over a tow-year period. In support of the trial, the coordinating center: prepares and distributes all study documents, including the protocol, manual of procedures, and study forms; designs and implements a data management system; monitors and reports on trial progress; develops and implements trialwide quality control procedures; contacts with a central laboratory and a food analysis laboratory to provide analysis of blood, urine, and food speciments; develops a mechanism for randomizing study participants; caries out data analysis for the trial; conduct site visits; organizes central training and certification of staff; establishes a system of trialwide communications; and provides logistical support to the trial. The proposed DASH2 trial extends research on sodium intake and dietary patterns to address several issues of great relevance to clinical practice and public health. Sodium reduction, coupled with the dietary pattern, has great promise to lower blood pressure to an extent hitherto not demonstrated for any nonpharamacologic treatment and may be an alternative to drug therapy for persons with stage 1 hypertension or high normal blood pressure. For persons with moderate-to-severe hypertension, it may reduce medication requirements and simplify treatment.
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