DASH

From Wiki Journal Club
Jump to: navigation, search
Appel LJ, et al. "A clinical trial of the effects of dietary patterns on blood pressure". The New England Journal of Medicine. 1997. 336(16):1117-1124.
PubMedFull textPDF

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.

Design

  • Multicenter, non-blind, parallel-group, randomized, controlled trial
  • N=459
    • Diet rich in fruits & vegetables (n=154)
    • Combination diet (n=151)
    • 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

  1. Neaton JD, et al. "Treatment of mild hypertension study." JAMA. (1993)270;6: 713-724.
  2. 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.
  3. 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.