The DASH sodium study was conducted by the National Heart, Lung, and Blood Institute (NHLBI) after completion of the Dietary Approaches to Stop Hypertension (DASH) study.
The first DASH study looked at whether a diet rich in fruit, vegetables, whole grains and low-fat dairy foods was protective against hypertension. Once the DASH diet was found to be successful at reducing high blood pressure, the investigators decided to look at whether the diet could be even more effective if it was also low in salt. The researchers examined the effects of three different levels of salt intake among participants following the diet.
The study included 412 adult participants who were either prehypertensive or stage 1 hypertensive. Around 41% of the participants had high blood pressure, 57% were women and 57% were African American. The study was conducted between September 1997 and November 1999.
The study participants were divided into two groups: those who followed the DASH diet and those who ate a typically American diet. Each of the diets were also subdivided by three different daily intakes of sodium which included:
- High intake of about 3300 milligrams per day (this is typical in most American diets)
- Intermediate intake of about 2400 milligrams per day
- Low intake of about 1500 milligrams per day
The results of the study showed that for both diets, blood pressure was lower in the groups that had a lower daily salt intake. However, for each of the sodium levels, blood pressure was significantly lower among those following the DASH diet compared with those following the American diet.
The greatest reduction in blood pressure was seen among those who followed the DASH diet with the low salt intake. Further analysis showed that the African-American participants (who are genetically predisposed to high blood pressure) showed significant reductions in blood pressure after following the DASH diet with the low salt intake. Furthermore, greater reductions in blood pressure were observed among those with high blood pressure than in individuals with normal blood pressure.