The DASH diet, sodium intake and blood pressure trial (DASH-sodium): Rationale and design

The DASH Diet, Sodium Intake and Blood Pressure Trial (DASH-Sodium) is a mu lticenter, randomized trial comparing the effects of 3 levels of sodium int ake and 2 dietary patterns on blood pressure among adults with higher than optimal blood pressure or with stage 1 hypertension (120-159/80-95 mm Hg). The 2 dietary patterns are a control diet typical of what many Americans ea t, and the DASH diet, which, by comparison, emphasizes fruits, vegetables, and low-fat dairy foods, includes whole grains, poultry, fish, and nuts, an d is reduced in fats, red meat, sweets, and sugar-containing beverages. The 3 sodium levels are defined as higher (typical of current US consumption), intermediate (reflecting the upper limit of current US recommendations), a nd lower (reflecting potentially optimal levels). Participants are randomly assigned to 1 of the 2 dietary patterns using a parallel group design and are fed each of the 3 sodium levels using a randomized crossover design. Th e study provides participants with all of their food during a 2-week run-in feeding period and three 30-day intervention feeding periods. Participants attend the clinic for 1 meal per day, 5 days per week, and take home food for other meals. Weight is monitored and individual energy intake adjusted to maintain baseline weight. The primary outcome is systolic blood pressure measured at the end of each intervention feeding period. Systolic blood pr essure is compared across the 3 sodium levels within each diet and across t he 2 diets within each sodium level. If effects previously observed in clin ical trials are additive, sodium reduction and the DASH diet together may l ower blood pressure to an extent not as yet demonstrated for nonpharmacolog ic treatment. The DASH-Sodium results will have important implications for the prevention and treatment of high blood pressure.