Effectiveness of the DASH Diet at Reducing High Blood Pressure
|Cardiovascular Diseases Hypertension Heart Diseases||Behavioral: Dietary Approaches to Stop Hypertension (DASH) Behavioral: Control Diet|
|Study Design:||Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double Blind (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary Purpose: Prevention
|Official Title:||Cardiovascular and Renal Hemodynamics and the DASH Diet|
- Changes in central aortic stiffness, diastolic relaxation, renal blood flow,and vascular response to Ang II [ Time Frame: Measured at 4 weeks ]
|Study Start Date:||January 2006|
|Study Completion Date:||October 2014|
|Primary Completion Date:||June 2009 (Final data collection date for primary outcome measure)|
Active Comparator: 1
Dietary Approaches to Stop Hypertension (DASH)
Behavioral: Dietary Approaches to Stop Hypertension (DASH)
4 week feeding intervention
Placebo Comparator: 2
Behavioral: Control Diet
4 week feeding intervention
The study expands upon the findings of the Dietary Approaches to Stop Hypertension (DASH) study, which showed that a dietary pattern emphasizing fruits, vegetables, and low fat dairy products and overall reduced in total and saturated fat significantly lowers blood pressure (BP). The DASH diet is particularly effective in African Americans and in individuals with systolic hypertension. However, it is not known if the DASH diet affects the pathophysiology of the hypertensive process. Preliminary data support the possibility that the DASH diet interrupts the renin-angiotensin system. This raises the intriguing possibility that the DASH diet will favorably impact on cardiovascular and renal hemodynamics in patients with isolated systolic hypertension. Therefore, the central hypothesis of this study is that the DASH diet affects central aortic stiffness, diastolic relaxation, and renal and vascular reactivity to angiotensin II (Ang II) by lowering tissue renin-angiotensin system activity.
A randomized, crossover design will be used to compare the DASH diet to a control diet as defined in the original DASH protocol (NEJM 1997; 336:1117). Fifty-five community-dwelling individuals age 20 and older with systolic blood pressure (SBP) 140-179 mmHg and diastolic blood pressure (DBP) less than 90 mmHg will enter a 1-week run-in period eating both the control and DASH diets for 3-4 days each. Following this, participants will begin two 4-week intervention feeding periods receiving either the DASH diet or the control diet in random order. Clinical measurements will be taken at the conclusion of each 4-week feeding period.
Outcome measures: Specific measurements will include peripheral and renal vascular response to Ang II infusions, renal blood flow measured by para-aminohippurate (PAH) clearance, conduit vessel hemodynamics, and tissue Doppler imaging (TDI). At the end of each intervention feeding period, the clinical measurements will be made before and after acute administration of captopril, an angiotensin converting enzyme (ACE) inhibitor.
The study will test whether the DASH diet (1) lowers central aortic stiffness as measured by vascular impedance and carotid-femoral pulse wave velocity; (2) improves diastolic relaxation as measured by early diastolic myocardial velocities across the mitral valve (Ea); (3) vasodilates renal blood flow and enhances vascular responses to Ang II; and (4) affects central aortic stiffness, diastolic relaxation, renal blood flow, and renal and vascular reactivity to Ang II by altering target tissue responsiveness to Ang II similar to ACE inhibition.
Please refer to this study by its ClinicalTrials.gov identifier: NCT00123006
|Principal Investigator:||Paul R. Conlin, MD||Brigham and Women's Hospital|