The Dietary Approaches to Stop Hypertension Study
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The Dietary Approaches to Stop Hypertension Study |
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For many years, health professionals have recommended sodium restriction, weight loss (for overweight individuals), and reduction of alcohol intake (in heavy drinkers) to lower blood pressure. While a vegetarian diet is also associated with lower blood pressure, studies that have assessed the blood pressure effect of various components of vegetarian diets have failed to identify its "active" ingredient.
The goal of the Dietary Approaches to Stop Hypertension (DASH) study was to test dietary patterns -- whole foods rather than isolated components. The researchers attempted to find a diet that retained the blood pressure benefits of the vegetarian diet but included enough meat products to make the diet palatable and acceptable to the general population.
Researchers at six major medical centers around the nation placed 459 people on one of three diets for 8 weeks. Salt content was similar for all diets, alcohol intake (by subject report) did not change during the trial, and body weight was kept constant by adjusting calorie intake as necessary. One group followed an eating plan that included nearly 10 servings of fruit and vegetables a day and low-fat dairy foods (the combination diet). The combination diet was also low in total fat (27% of calories) and saturated fat (7% of calories).
A second group ate a diet that provided about 8 servings of fruit and vegetables a day (the fruit/vegetable diet). This was a higher-fat plan, providing 37% of calories as fat. A third group followed a typical American diet that provided fewer than 4 servings of fruits and vegetables daily and 37% calories as fat (control diet).
The combination diet rich in fruits, vegetables, and low-fat dairy products with reduced saturated fat and total fat significantly lowered systolic pressure by 5.5 mm Hg and diastolic pressure by 3.0 mm Hg compared to the control diet. The effect of the diet was evident within one week and was maximal and stable at two weeks and thereafter. The fruit/vegetable diet exhibited about half the blood pressure effect of the combination diet -- systolic pressure fell 2.8 mm Hg and diastolic pressure fell 1.1 mg Hg compared to the control diet.
The reductions in blood pressure were greatest in the 133 subjects with stage 1 hypertension. The combination diet reduced systolic pressure by 11.4 mm Hg and diastolic pressure by 5.5 mm Hg compared to the control diet. These reductions are similar in magnitude to those seen in patients who begin drug therapy.
The results of DASH should be broadly applicable to the general population as the study subjects were 51% men and 49% women, covered a broad mix of ethnicity (two-thirds were minorities), and their baseline blood pressure levels matched 40% of the U.S. adults. The researchers estimate that if all Americans followed the DASH diet and experienced similar results, the incidence of coronary heart disease would be reduced by 15% and stroke by 27%.
The DASH web site (http://dash.bwh.harward.edu) recommends combining the diet with established non-drug interventions -- choosing foods lower in salt and sodium, keeping a healthy weight, being physically active, and drinking alcohol in moderation. The DASH diet offers an additional nutritional approach and possible alternative to medication usage in the treatment of mild hypertension and may prevent or delay the use medication for borderline hypertension.
The DASH eating plan shown below is based on 2,000 calories a day. Depending on calorie needs, the number of daily servings in a food group may vary from those listed.
Food Group Daily Number of Servings 1 Serving
Grains and 7-8 1 slice bread grain products ½ cup dry cereal
½ cup cooked pasta, rice or cereal
Vegetables 4-5 1 cup raw leafy vegetable
1 cup cooked vegetable
6 oz. vegetable juice
Fruit 4-5 1 medium fruit
½ cup fresh, frozen, or canned fruit
½ cup dried fruit
6 oz. fruit juice
Low-fat or non-fat 2-3 8 oz. milk
dairy foods 1 cup yogurt
1.5 oz. cheese
Lean meats, 2 or less 3 oz. cooked meats,
poultry, or fish skinless poultry, or fish
Nuts and other ½ 1.5 oz. or ½ cup nuts
alternatives 2 Tbsp. seeds
to meat ½ cup cooked legumes
References:
Lawrence J. Appel, M.D., M.P.H., et al. A clinical trial of the effects of dietary patterns
on blood pressure. New Eng. J. Med. 1997; 336:1117.
Ellen Coleman,
RD, MA, MPH
ellen@cruciblefitness.com
