DASH
PubMed • Full text • PDF
Clinical Question
In patients with chronic HTN, does a diet rich in fruits, vegetables, and low-fat dairy and low in saturated fats reduce blood pressure?
Bottom Line
In patients with SBP<160 and DBP 80-90, DASH diet rich in fruits and vegetables, low in saturated fats significantly reduced BP.
Major Points
Several trials have evaluated non-pharmacologic approaches to lowering BP, including dietary and behavioral modifications. For example, TOMHS trial (1993)[1] evaluated a program of weight reduction, sodium restriction, and exercise. The DASH trial (1997) evaluated a combination diet which is known today as the DASH diet, and the DASH-sodium study (2001)[2] evaluated sodium restriction in addition to the DASH diet. Most recently, the PREMIER trial (2003)[3] also assessed the DASH diet with or without dietary/behavioral modification, such as weight loss, physical activity, and limitations in sodium and alcohol intake.
The Dietary Approaches to Stop Hypertension (DASH) trial randomized 459 patients with SBP <160mmHg and DBP 80-95mmHg to a control diet, a diet rich in fruits and vegetables, or a combination diet rich in fruits and vegetables as well as low in saturated and total fat. This occurred in the setting of reduced sodium chloride intake and alcohol consumption recommended for all patients. The DASH trial demonstrated that the diet rich in fruits and vegetables reduced BP by 2.8/1.1 mmHg over control, while the combination diet reduced BP by 5.5/3.0 mmHg over control. The effects on BP reduction were seen within two weeks and were sustained for 6 more weeks. In a subset analysis, the efficacy of the combination diet was particularly marked among hypertensive patients, decreasing BP by 11.4/5.5 mmHg. This was similar in magnitude to that observed in trials of drug monotherapy for stage I HTN, suggesting that a combination diet may prevent or delay initiation of pharmacologic therapy in this population. The combination diet also decreased BP by 3.5/2.1 mmHg among non-hypertensive patients, suggesting that a combination diet may be an effective non-pharmacologic approach to preventing HTN. Although the trial was not designed to assess the long-term effects of dietary modifications, the DASH diet has major implications for CAD and stroke reduction.
Guidelines
2017 ACC AHA AAPA ABC ACPM AGS APhA ASH ASPC NMA PCNA Hypertension (2017, adapted)[4]
- In adults with elevated BP or hypertension (all COR I, LOE A):
- Recommend weight loss to lower BP if overweight or obese
- Recommend DASH diet or a heart-healthy diet facilitating desirable weight
- Recommend sodium reduction
- Increased physical activity with a structured exercise program
Design
- Multicenter, non-blind, parallel-group, randomized, controlled trial
- N=459
- Diet rich in fruits & vegetables (n=154)
- Combination diet (n=151)
- This is what's now known as the DASH diet
- Control diet (n=154)
- Enrollment: September 1994 to January 1996
- Analysis: Intention-to-treat
- Primary outcome: Change in resting DBP
Population
Inclusion Criteria
- Age ≥22 years
- mean SBP <160mmHg
- mean DBP 80-95mmHg
Exclusion Criteria
- Use of medications that affect BP
- Poorly controlled DM
- HL
- CV event within prior 6 mos
- CKD
- Chronic diseases that may interfere with study participation
- Pregnany or lactation
- BMI >35 kg/m2
- Unwilling to stop vitamins, mineral supplements, or antacids containing Mg or Ca
- >14 alcoholic drinks/wk
Baseline Characteristics
- Mean age: 44 years
- Female: 49%
- White: 34%
- Black: 59.9%
- BMI: 27.8 in males, 28.7 in females
- Alcohol: 1.2 drinks/wk
- SBP: 132mmHg (23.5% ≥140mmHg)
- DBP: 85mmHg (13.7% ≥90mmHg)
- Household income:
- <$30,000: 36.6%
- $30,000-%59,999: 40.4%
- ≥$60,000: 23.1%
Interventions
Phases
- Screening: 3 visits; BP measurements, physical activity recall questionnaire
- Run-in: 3 weeks of control diet; BP measurements, 24-hour urine collection, symptoms questionnaire
- Intervention: 8 weeks of assigned diets; BP measurements, 24-hour urine collection, symptoms and physical activity recall questionnaires
Diets
- Control: 3g Na; K, Mg, Ca levels at 25th %ile US consumption; fiber and macronutrients at mean US consumption
- 1-2 servings of fruit, 2 servings of vegetable, 5-6 servings of fat, oils, salad dressing, 4 servings of snacks/sweets
- Fruits & vegetable: 3g Na; K, Mg at 75th %ile US consumption; high fiber, more fruits & vegetables
- 5 servings of fruit, 3-4 servings of vegetable, 5-6 servings of fat, oils, salad dressing, 1-2 servings of snacks/sweets
- Combination diet: 3g Na; K, Mg, Ca at 75th %ile US consumption; high fiber, more fruits & vegetables; low-fat dairy; low in saturated and total fats
- 5 servings of fruit, 4-5 servings of vegetable, 2 servings of low-fat dairy, 2-3 servings of fat, oils, and salad dressing, <1 serving of snacks/sweets
- ≤3 caffeinated beverages and ≤2 alcoholic beverages per day
Outcomes
Primary Outcomes
- Changes in resting DBP
- Combination vs. control: -3.0mmHg (97.5% CI -4.3 to -1.6; P<0.001)
- Combination vs. fruits & vegetables: -1.9 mmHg (97.5% CI -3.3 to -0.6; P=0.002)
- Fruits & vegetables vs. control: -1.1 mmHg (97.5% CI -2.4 to 0.3; P=0.07)
Secondary Outcomes
- Changes in resting SBP
- Combination vs. control: -5.5mmHg (97.5% CI -7.4 to -3.7; P<0.001)
- Combination vs. fruits & vegetables: -2.7 mmHg (97.5% CI -4.6 to -0.9; P=0.001)
- Fruits & vegetables vs. control: -2.8 mmHg (97.5% CI -4.7 to -0.9; P<0.001)
- Changes in ambulatory DBP
- Combination vs. control: -2.7mmHg (P<0.001)
- Fruits & vegetables vs. control: -2.1mmHg (P=0.002)
- Changes in ambulatory SBP
- Combination vs. control: -4.5 mmHg (P<0.001)
- Fruits & vegetables vs. control: -3.1 mmHg (P=0.001)
Subgroup Analysis
Comparisons are combination vs. control.
- Among hypertensives
- Changes in resting DBP: -5.5 (P<0.001)
- Changes in resting SBP: -11.4 (P<0.001)
- Among non-hypertensives
- Changes in resting DBP: -2.1 (P=0.003)
- Changes in resting SBP: -3.5 (P<0.001)
- Among minority
- Changes in resting DBP: -3.5 (P<0.001)
- Changes in resting SBP: -6.8 (P<0.001)
- Among non-minority
- Changes in resting DBP: -2.0 (P=0.04)
- Changes in resting SBP: -3.0 (P=0.02)
Adverse Events
- 9% developed moderate to severe constipation during run-in phase
- At end of intervention phase, constipation occurred in 10.1% of control arm, 5.4% of fruits & vegetables arm, and 4.0% of combined arm.
Criticisms
- Not designed to assess long-term effects of diets on BP or CV events
Funding
- Supported by grants from National Heart, Lung, and Blood Institute, Office of Research on Minority Health, and National Center for Research Resources of National Institutes of Health
- Multiple companies donated food.
Further Reading
- ↑ Neaton JD, et al. "Treatment of mild hypertension study." JAMA. (1993)270;6: 713-724.
- ↑ Sacks FM, et al. "Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet." New England Journal of Medicine(2001)344;1:3-10.
- ↑ Appel LJ, et al. "Effects of comprehensive lifestyle modification on blood pressure control: main results of the PREMIER clinical trial." JAMA: the journal of the American Medical Association(2003): 289;16:2083-2093.
- ↑ Whelton PK et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Hypertension 2017. :.