Effectiveness of the DASH Diet at Reducing High Blood Pressure

Hypertension Clinical Trial

Official title:

Cardiovascular and Renal Hemodynamics and the DASH Diet

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT00123006
• Other study ID #: 229
• Secondary ID: R01HL077234
• Status: Completed
• Phase: N/A
• First received: July 20, 2005
• Last updated: January 12, 2016
• Start date: January 2006
• Est. completion date: October 2014

Study information

• Verified date: January 2016
• Source: Brigham and Women's Hospital
• Contact: n/a
• Is FDA regulated: No
• Health authority: United States: Federal Government
• Study type: Interventional

Clinical Trial Summary

The purpose of this study is to test the effects of the DASH diet in patients with isolated systolic hypertension.

Description:

BACKGROUND:

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.

DESIGN NARRATIVE:

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.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 44
• Est. completion date: October 2014
• Est. primary completion date: June 2009
• Accepts healthy volunteers: No
• Gender: Both
• Age group: 20 Years to 80 Years

Eligibility

Inclusion Criteria:

• Isolated systolic hypertension: systolic blood pressure (SBP) in the range of 140-179 mm Hg and diastolic blood pressure (DBP) less than 90 mm Hg

• Body mass index (BMI) less than 40

• Current use of fewer than two blood pressure medications (which will be withdrawn prior to study)

Exclusion Criteria:

• Major concomitant diseases that may include but are not limited to active pulmonary disease within the past 6 months

• History of cardiovascular disorders such as angina, heart attack, heart failure, or stent placement

• Active gastrointestinal disease, including prior gastrointestinal surgery

• Renal disease with serum creatinine greater than 1.5 mg/dl (men) or 1.4 mg/dl (women)

• Insulin-dependent diabetes mellitus

• Current pregnancy

Study Design

Allocation: Randomized, Intervention Model: Crossover Assignment, Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes Assessor), Primary Purpose: Prevention

Related Conditions & MeSH terms

• Cardiovascular Diseases
• Heart Diseases
• Hypertension

Intervention

Behavioral:
• Dietary Approaches to Stop Hypertension (DASH)
4 week feeding intervention
• Control Diet
4 week feeding intervention

Locations

Country	Name	City	State
n/a

Sponsors (2)

Lead Sponsor	Collaborator
Brigham and Women's Hospital	National Heart, Lung, and Blood Institute (NHLBI)

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Changes in central aortic stiffness, diastolic relaxation, renal blood flow,and vascular response to Ang II		Measured at 4 weeks	No