Interactions of the DASH Diet with the Renin-Angiotensin-Aldosterone System

BACKGROUND: The Dietary Approaches to Stop Hypertension (DASH) diet is widely recommended to lower blood pressure, but its mechanisms of action are unclear. Lines of evidence suggest an interaction with the renin-angiotensin-aldosterone system (RAAS). OBJECTIVE: We conducted a randomized, controlled, cross-over feeding trial to test RAAS-related mechanisms underlying the DASH diet in patients with isolated systolic hypertension. METHODS: Participants entered a 1-wk run-in period on a control (CON) diet and then consumed the DASH or CON diets for 4 wk each in randomized sequence. Calorie content was controlled to maintain weight, and sodium intake was set at 3 g daily. After each diet, participants had hormonal and hemodynamic assessments obtained at baseline, in response to RAAS inhibition with captopril (CAP) 25 mg, and to graded angiotensin II (AngII) infusions (1 ng/kg and 3 ng/kg × 45 min). Primary outcomes were mean arterial pressure (MAP) and renal blood flow (RBF), and secondary outcomes were diastolic function, pulse wave velocity (PWV), plasma renin activity (PRA), and aldosterone (ALDO) responses by diet. RESULTS: In total, 44 (19 female) participants completed the study. DASH + CAP significantly lowered MAP compared with CON + CAP (83 ± 11 mmHg compared with 88 ± 14 mmHg, P <0.01). RBF was increased with DASH + CAP compared with CON + CAP (486 ± 149 cc/min compared with 451 ± 171 cc/min, P <0.001). Study diet did not change PWV but CAP reduced diastolic function on the DASH diet (P <0.05). DASH + CAP significantly increased PRA compared with CON + CAP (1.52 ± 1.78 ng/mL/min compared with 0.89 ± 1.17 ng/mL/min; P <0.001). ALDO sensitivity to AngII infusion was greater with DASH when compared to CON (17.4 ± 7.7 ng/mL compared with 13.8 ± 6.2 ng/dL, P <0.05) as was DASH + CAP compared with CON + CAP (15.1 ± 5.3 ng/dL compared with 13.1 ± 5.9 ng/mL, P <0.05). CONCLUSIONS: The DASH diet interacts with the RAAS resulting in vascular and hormonal responses similar to a natriuretic effect, which appears to augment the hypotensive effect of angiotensin-converting enzyme (ACE) inhibition in individuals with isolated systolic hypertension. This trial was registered at clinicaltrials.gov as NCT00123006.