DASH Diet - DASH-Sodium Study Design

DASH-Sodium Study Design

The DASH-Sodium study was conducted following the end of the original DASH study to determine whether the DASH diet could produce even better results if it were low in salt and also to examine the effects of different levels of sodium in people eating the DASH diet. The researchers were interested in determining the effects of sodium reduction when combined with the DASH diet as well as the effects of the DASH diet when at three levels of sodium intake. The DASH-Sodium trial was conducted from September 1997 through November 1999. Like the previous study, it was based on a large sample (412 participants) and was a multi-center, randomized, outpatient feeding study where the subjects were given all their food. The participants were adults with prehypertension or stage 1 hypertension (average systolic of 120 to 159 mm Hg & average diastolic of 80 to 95 mm Hg) and were randomly assigned to one of two diet groups. The two randomized diet groups were the DASH diet and a control diet that mirrored a “typical American diet”, and which was somewhat low in key nutrients such as potassium, magnesium and calcium. The DASH diet was the same as in the previous DASH study. After being assigned to one of these two diets, the participants were given diets that differed by 3 distinct levels of sodium content, corresponding to 3,000 mg, 2,400 mg or 1,500 mg/day (higher, intermediate or lower), in random order, for 30 consecutive days each. During the two week run-in phase, all participants ate the high sodium control diet. The 30 day intervention phase followed, in which subjects ate their assigned diets at each of the aforementioned sodium levels (high, intermediate and low) in random order, in a crossover design. During the 30 day dietary intervention phase, each participant therefore consumed his or her assigned diet (either DASH or control) at all three sodium levels.