DPSIBP is a four-center, randomized clinical trial designed to compare the effects of two dietary patterns and three levels of sodium intake on blood pressure. This application, from the DPSIBP Clinical center at Johns Hopkins, is one of a coordinated set of applications from the five participating institutions. The two dietary patterns are a """"""""reference diet"""""""" that is typical of what Americans generally eat and an """"""""intervention diet that is described in the coordinating center's application. 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 these 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 (defined as 80-89 mm Hg DBP) or with Stage 1 (mild) hypertension (defined as 90-95 mm Hg DBP). Half are African American and half are female. Participants attend a series of three eligibility screening visits followed by a two-week run-in feeding period and a four-week intervention feeding period 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 two weeks 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 to take home food to eat for their other meals. Clinics will deliver the interventions in four successive cohorts, with approximately 25 randomized participants per cohort, over a two-year period. In support of the trial this clinical center will: actively participate in trialwide committees; recruit and randomize 100 participants meeting study eligibility criteria, half of whom are African American and half of whom are female; assist in the development of the study menus; acquire, store, and prepare foods according to the trial protocol; monitor compliance with the trial's eating requirements; collect and process clinical and food specimens according to protocol; collect and process all other study data per protocol; work with participants to help ensure their compliance; and monitor local operations to assure they meet adequate levels of quality control.
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