Effects of the DASH diet alone and in combination with exercise and weight loss on blood pressure and cardiovascular biomarkers in men and women with high blood pressure: the ENCORE study

Abstract

Background: Although the DASH (Dietary Approaches to Stop Hypertension) diet has been shown to lower blood pressure (BP) in short-term feeding studies, it has not been shown to lower BP among free-living individuals, nor has it been shown to alter cardiovascular biomarkers of risk.

Objective: To compare the DASH diet alone or combined with a weight management program with usual diet controls among participants with prehypertension or stage 1 hypertension (systolic BP, 130-159 mm Hg; or diastolic BP, 85-99 mm Hg).

Design and setting: Randomized, controlled trial in a tertiary care medical center with assessments at baseline and 4 months. Enrollment began October 29, 2003, and ended July 28, 2008.

Participants: Overweight or obese, unmedicated outpatients with high BP (N = 144).

Interventions: Usual diet controls, DASH diet alone, and DASH diet plus weight management.

Outcome measures: The main outcome measure is BP measured in the clinic and by ambulatory BP monitoring. Secondary outcomes included pulse wave velocity, flow-mediated dilation of the brachial artery, baroreflex sensitivity, and left ventricular mass.

Results: Clinic-measured BP was reduced by 16.1/9.9 mm Hg (DASH plus weight management); 11.2/7.5 mm (DASH alone); and 3.4/3.8 mm (usual diet controls) (P < .001). A similar pattern was observed for ambulatory BP (P < .05). Greater improvement was noted for DASH plus weight management compared with DASH alone for pulse wave velocity, baroreflex sensitivity, and left ventricular mass (all P < .05).

Conclusion: For overweight or obese persons with above-normal BP, the addition of exercise and weight loss to the DASH diet resulted in even larger BP reductions, greater improvements in vascular and autonomic function, and reduced left ventricular mass.

Clinical trial registration: clinicaltrials.gov Identifier: NCT00571844.

Figure 1

Participant flow in the ENCORE (Exercise and Nutrition interventions for CardiOvasculaR hEalth) clinical trial. BMI indicates body mass index (calculated as weight in kilograms divided by height in meters squared); BP, blood pressure; DASH, Dietary Approaches to Stop Hypertension; and ITT, intent-to-treat.

Figure 2

Comparison of posttreatment means and 95% confidence intervals for clinic-measured blood pressure (BP) using an intent-to-treat model, adjusted for age, sex, ethnicity, and pretreatment BP. The contrasts between all active treatment groups and the usual diet control (UC) group were significant for both systolic (A) and diastolic (B) BP (P < .001), as were the contrasts between DASH-WM (Dietary Approaches to Stop Hypertension plus weight management) vs DASH-A (DASH alone) for systolic BP (P = .02) and diastolic BP (P = .048). The right panels display the pairwise differences (mean difference and 95% confidence interval) between the treatment groups calculated from the adjusted posttreatment means.

Figure 3

Comparison of posttreatment means and 95% confidence intervals for 24-hour ambulatory blood pressure (BP) using an intent-to-treat model, adjusted for age, sex, ethnicity, percentage of time in sitting or standing position, and pretreatment BP. The contrast between all active treatment groups and the usual diet control (UC) group was significant for systolic (A) and diastolic (B) BP (P < .001), as were the contrasts between DASH-WM (Dietary Approaches to Stop Hypertension plus weight management) vs DASH-A (DASH alone) for systolic BP (P = .01) and diastolic BP (P = .03). The right panels display the pairwise differences (mean difference and 95% confidence intervals) between the treatment groups calculated from the adjusted posttreatment means.

Figure 4

Comparison of posttreatment mean (95% confidence interval) values for pulse wave velocity (A), flow-mediated dilation (B), baroreflex sensitivity (C), and left ventricular (LV) mass index (D) by treatment group, adjusted for age, sex, ethnicity, and pretreatment level of response variable. Flow-mediated dilation of the brachial artery also was adjusted for pretreatment arterial diameter at rest. Results of contrasts were as follows: for pulse wave velocity (A), all treatments vs usual diet controls (UC), P = .002, and DASH-WM (Dietary Approaches to Stop Hypertension plus weight management) vs DASH-A (DASH alone), P = .045; for flow-mediated dilation (B), all treatments vs UC, P = .06, and DASH-WM vs DASH-A, P = .99; for baroreflex sensitivity (C), all treatments vs UC, P = .38, and DASH-WM vs DASH-A, P = .01; and for left ventricular mass index (D), all treatments vs UC, P = .26, and DASH-WM vs DASH-A, P = .02.