Introduction

First published in 1997, the DASH diet study results were impressive. The DASH eating plan reduced blood pressure in men, women, younger and older persons, minorities and non-minorities and in people with and without hypertension. With a maximum benefit noted after just two weeks, the DASH diet?s blood pressure reduction was most significant in minority and hypertensive groups. The follow-up DASH-Sodium Trial supported the role of sodium restriction in blood pressure management, showing DASH was even more effective along with a sodium restriction. Additional DASH diet research has linked the DASH diet pattern to lower LDL-cholesterol levels, improved homocysteine levels, and improve insulin sensitivity. DASH went mainstream in 2005, when the DASH eating plan was recommended as part of the 2005 Dietary Guidelines for Americans.

One in four American adults have hypertension, defined as blood pressure readings at or above 140 mm Hg systolic and/or 90 mm Hg diastolic. Hypertension poses an increased risk of heart disease, stroke and kidney failure. Controlling blood pressure significantly reduces these health risks. For a person with hypertension, adopting the DASH eating plan is estimated to reduce systolic blood pressure by 8-14 mm Hg. According to DASH diet researchers, if everyone in the United States adopted the DASH eating plan, the incidence of Coronary Artery Disease would be reduced by 15% and the incidence of stroke reduced by 27%. (Appel, et al., 1997).

This course will review the DASH diet research methodology and results, describe the DASH eating plan in detail, and discuss the practical implementation of the DASH eating plan. This course is designed for dietitians and other health professionals who work with hypertensive clients.

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The DASH Diet Study

The purpose of the DASH Trial was to compare the effect of three dietary patterns on blood pressure: an average American diet, a diet with plentiful fruits and vegetables and a combination diet. This combination diet (referred to in this course as the DASH diet) combined many factors known or believed to influence blood pressure. The DASH diet was 2.5 times higher in potassium, magnesium and calcium, and three times higher in fiber compared to the control diet. The DASH diet was also slightly higher in protein, and lower in fat, cholesterol and sweets compared to control.

The study group included 459 adults, age 22 or above. Study participants had an average systolic blood pressure below 160 mm Hg and diastolic blood pressure of 80-95 mm Hg, and needed to maintain those levels without antihypertensive medications. Twenty seven percent of the study population had stage 1 hypertension (defined as systolic 140-159 mm Hg or diastolic 90-99 mm Hg) and the rest has pre-hypertension (defined as systolic 120-139 mm Hg or systolic of 80-89 mm Hg). Excluded from the study were those with poorly controlled diabetes, cardiovascular event within the past six months, hyperlipidemia, BMI above 35, pregnancy or lactation, renal insufficiency, or a chronic disease that may interfere with participation. Also excluded were those who drank more than 2 drinks of alcohol per day, anyone taking medications that affect blood pressure, or anyone unwilling to stop vitamin or mineral supplements or magnesium containing antacids.

Additional information about the study population:

• Male to female ratio 1:1
• 59% African American, 35% Caucasian
• Annual income
  • <$30,000 37%
  • $30,000-59,999 43%
  • >$60,000 20%
• Mean BMI 28
• Baseline BP 132/85
  (Appel, 1997)

DASH Eating Plans

1. The average American diet (The Control Diet)
2. The average American diet rich in fruits and vegetables (The Fruit and Vegetable Plan)
3. The DASH diet: low in saturated fat, rich in fruits, vegetables, whole grains, nonfat & lowfat dairy products.

• The control diet was typical of the fiber, carbohydrate, protein and fat profiles of the average American, and representative of the 25th percentile of U.S. consumption of potassium, magnesium and calcium. (Appel, 1997).
• The fruit and vegetable plan was higher in fiber, potassium and magnesium than the control diet.
• Compared to the control diet, the DASH diet was lower in total fat, saturated fat and higher in carbohydrate, protein, fiber, potassium, magnesium and calcium.