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United States Department of Agriculture

Agricultural Research Service

DASH away threat of high blood pressure
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By W. Thomas Johnson

Hypertension is a prevalent problem in our society. About 25 percent of American adults have high blood pressure and in people aged 60 years and older, the incidence is even higher at about 50 percent.

Blood pressure is recorded as two numbers systolic pressure, measured as the heart beats, and diastolic pressure, measured between beats. High blood pressure occurs when systolic pressure is 140 or higher and diastolic pressure is 90 or higher.

While high blood pressure raises the risk for heart disease and stroke, the risk actually starts increasing when blood pressure creeps above what is considered the normal systolic pressure of 120 and normal diastolic pressure of 80. Thus, blood pressure is healthiest when systolic pressure is less than 120 and diastolic pressure is less than 80.

Unfortunately, less than half of all people in the United States have healthy blood pressure.

When people think of dieting, they generally think in terms of weight loss or obesity prevention.

As a result, many are familiar with diets, such as the Atkins and South Beach diets.

Fewer people seem to know about the DASH diet, which is a proven dietary intervention for reducing blood pressure. This diet comes from a landmark scientific study called Dietary Approaches to Stop Hypertension, or DASH.

Before DASH, it was recognized that vegetarians, who eat fruits, vegetables and grains that are rich in potassium, magnesium, and fiber, had low blood pressure. People who ate more protein also tended to have lower blood pressure.

However, trials involving increased consumption of individual nutrients, such as potassium, magnesium, calcium or fiber, only slightly their lowered blood pressure. As a result, the DASH study employed a whole-diet approach with the idea that the combination of individual nutrients may produce an additive effect for lowering blood pressure.

The initial DASH study involved 459 adults having systolic pressures less than 160 and diastolic pressures of 80 to 95. About 30 percent of the people in the study had high blood pressure.

The participants were fed one of three diets for eight weeks. The control diet contained the average amount of fat and cholesterol found in a typical diet and less than the average amounts of potassium, magnesium and calcium.

Another diet, the fruit and vegetable diet, provided the same amount of fat and cholesterol as the control diet, but boosted potassium, magnesium and fiber by using fruits and vegetables to replace snacks and sweets.

A third diet, the combination diet, provided less fat and cholesterol than either the control or fruit and vegetable diets, but was rich in fruits, vegetables and low-fat dairy products. Each of these diets had the same amount of calories and salt.

Results from the trial showed that the combination diet was best for lowering blood pressure. The combination diet produced an average reduction of 3.5 points in systolic pressure and 2.1 points in diastolic pressure. The results were even more impressive in the people who had hypertension. With the combination diet, they experienced a 11.4-point drop in systolic pressure and a 5.5-point drop in diastolic pressure.

In the DASH study, sodium (salt) intake from the three diets was kept constant at 3 grams per day. In a recent follow-up study, 412 participants ate either the control diet or the combination diet, now referred to as the DASH diet. Three control diets and three DASH diets were used that provided about 3.3 grams, 2.4 grams and 1.5 grams of salt per day.

After 30 days of eating these diets, the results showed that reducing salt lowered blood pressure in those eating both the control and DASH diets. However, the largest reductions in blood pressure occurred in the participants who ate the DASH diet with the lowest level of salt.

The results of the DASH studies provide an eating plan that is a proven way to lower blood pressure. Another good aspect of the DASH diet is that it is easy to follow. Just reduce fat intake, increase grain, fruit and vegetable intakes and use low-fat dairy products.

Information regarding serving sizes and recipes are readily available on the Internet by "Googling" DASH diet or going to www.nhlbi.nih.gov.

If you have high blood pressure or if you are taking medication for high blood pressure, talk to your doctor about your plans to try the DASH diet. You also should monitor your blood pressure frequently if you are on the DASH diet.

While the DASH diet can help lower pressure and help prevent blood pressure from creeping up with age, remember that losing excess weight, exercising and reducing salt intake are all part of an effective strategy for lowering blood pressure.


Last Modified: 9/20/2006
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