Dietary Approaches to Stop Hypertension (DASH) Diet and Blood Pressure Reduction in Adults with and without Hypertension: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Abstract

The Dietary Approaches to Stop Hypertension (DASH) diet is recognized as an effective dietary intervention to reduce blood pressure (BP). However, among randomized controlled trials (RCTs) investigating the DASH diet-mediated BP reduction, there are significant methodological and clinical differences. The purpose of this study was to comprehensively assess the DASH diet effect on BP in adults with and without hypertension, accounting for underlying methodological and clinical confounders. We systematically searched Medline and the Cochrane Collaboration Library databases and identified 30 RCTs (n = 5545 participants) that investigated the BP effects of the DASH diet compared with a control diet in hypertensive and nonhypertensive adults. Both random-effects and fixed-effect models were used to calculate the mean attained systolic BP (SBP) and diastolic BP (DBP) differences during follow-up. Subgroup and meta-regression analyses were also conducted. Compared with a control diet, the DASH diet reduced both SBP and DBP (difference in means: -3.2 mm Hg; 95% CI: -4.2, -2.3 mm Hg; P < 0.001, and -2.5 mm Hg; 95% CI: -3.5, -1.5 mm Hg; P < 0.001, respectively). Hypertension status did not modify the effect on BP reduction. The DASH diet compared with a control diet reduced SBP levels to a higher extent in trials with sodium intake >2400 mg/d than in trials with sodium intake ≤2400 mg/d, whereas both SBP and DBP were reduced more in trials with mean age <50 y than in trials of older participants. The quality of evidence was rated as moderate for both outcomes according to the Grading of Recommendations, Assessment, Development, and Evaluation approach. The adoption of the DASH diet was accompanied by significant BP reduction in adults with and without hypertension, although higher daily sodium intake and younger age enhanced the BP-lowering effect of the intervention. This meta-analysis was registered at www.crd.york.ac.uk/prospero as CRD42019128120.

Keywords: DASH; Dietary Approaches to Stop Hypertension; blood pressure; diet; hypertension; meta-analysis; randomized controlled trials; systematic review.

FIGURE 1

Preferred Reporting Items for Systematic Reviews and Meta-Analyses flow diagram of the study identification and selection process for eligible RCTs. DASH, Dietary Approaches to Stop Hypertension; RCT, randomized controlled trial.

FIGURE 2

BP-lowering effect of the DASH diet in adults with and without hypertension: total analysis for SBP and DBP outcomes and sensitivity analyses, according to clinical and methodological characteristics of the selected trials. Difference in means of attained SBP and DBP difference in trials investigating the effect of the DASH diet compared with a control diet. From left to right, the columns indicate the type of analysis, the number of trials analyzed, the number of subjects per randomized arm in each separate analysis for both BP outcomes, the heterogeneity in each analysis for each outcome, the difference in means and 95% CIs for each outcome under the appropriate model based on heterogeneity (the minus sign indicates a lower BP value in the first group), and the forest plots of the difference in means and 95% CIs (black = SBP reduction and gray = DBP reduction). BP, blood pressure; DASH, Dietary Approaches to Stop Hypertension; DBP, diastolic blood pressure; ITT, intention-to-treat; RCT, randomized controlled trial; SBP, systolic blood pressure.

FIGURE 3

BP-lowering effect of the DASH diet in adults with and without hypertension: subgroup analyses for SBP and DBP outcomes, according to clinical and methodological characteristics of the selected trials. Difference in means of attained SBP and DBP difference in trials investigating the effect of the DASH diet compared with control diet in different conditions: hypertension, normotension, untreated hypertension, treated hypertension, and stratified by the SBP threshold of 140 mm Hg. From left to right, the columns indicate condition, the number of trials analyzed, the number of subjects per randomized arm in each separate analysis for both BP outcomes, the heterogeneity in each analysis for each outcome, the difference in means and 95% CIs for each outcome under the appropriate model based on heterogeneity (the minus sign indicates a lower BP value in the first group), and the forest plots of the difference in means and 95% CIs (black = SBP reduction and gray = DBP reduction). BP, blood pressure; DASH, Dietary Approaches to Stop Hypertension; DBP, diastolic blood pressure; RCT, randomized controlled trial; SBP, systolic blood pressure.