History & Design of the DASH-Sodium Study

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. Primarily the researchers were interested in gaining more insight into the effect of sodium reduction when combined with the DASH diet. Design of the trials for the DASH-Sodium study were conducted and the trials took place 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. 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 an “average American diet”, and which was somewhat low in key nutrients such as potassium, magnesium and calcium. After being assigned to one of these two diets, and within their assignment the participants ate foods differentiated by 3 distinct levels of sodium content, corresponding to 3,000 mg, 2,400 mg or 1,500 mg/day (hi, intermediate or low), in random order, for 30 consecutive days. 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.