A clinical trial of the effects of dietary patterns on blood pressure. DASH Collaborative Research Group.
Level 2 - randomized trial
Individual multicenter randomized controlled feeding trial
PubMed 9099655 · doi:10.1056/NEJM199704173361601
What was done
In the multicenter Dietary Approaches to Stop Hypertension (DASH) trial, 459 adults with systolic blood pressure (SBP) < 160 mm Hg and diastolic blood pressure (DBP) 80 to 95 mm Hg were fed a standard US control diet (low in fruits, vegetables, and dairy) for a 3-week run-in period. Participants were then randomized for 8 weeks to one of three diets: the control diet, a diet rich in fruits and vegetables, or a combination diet rich in fruits, vegetables, and low-fat dairy products with reduced saturated and total fat. Sodium intake and body weight were held constant across groups.
What was found
Baseline mean blood pressure was 131.3 +/- 10.8 mm Hg SBP and 84.7 +/- 4.7 mm Hg DBP. Compared with the control diet, the combination diet lowered SBP by 5.5 mm Hg and DBP by 3.0 mm Hg (P < 0.001 for both). The fruits-and-vegetables diet lowered SBP by 2.8 mm Hg (P < 0.001) and DBP by 1.1 mm Hg (P = 0.07) relative to control. Among the 133 hypertensive participants (SBP >= 140 mm Hg or DBP >= 90 mm Hg), the combination diet reduced SBP by 11.4 mm Hg and DBP by 5.5 mm Hg more than control (P < 0.001 for both). Among 326 non-hypertensive participants, the combination diet reduced SBP by 3.5 mm Hg (P < 0.001) and DBP by 2.1 mm Hg (P = 0.003) more than control.
Why it matters
This trial established that an overall dietary pattern emphasizing fruits, vegetables, and low-fat dairy lowers blood pressure independently of sodium restriction or weight change, offering a non-pharmacological strategy for hypertension prevention and management.
Limits
The intervention lasted only 8 weeks, leaving long-term durability unaddressed. Because all food was provided to participants, the study does not capture real-world dietary adherence. Individuals with severe hypertension (SBP >= 160 mm Hg or DBP > 95 mm Hg) were excluded, and hard cardiovascular outcomes were not evaluated.