Published: Jan. 25, 2010
Updated: Jan. 25, 2010
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By Duke Medicine News and Communications
Adding exercise and weight loss to the nationally recommended DASH diet (Dietary Approaches to Stop Hypertension) reduced blood pressure equal to rates expected with use of medication alone, according to researchers at Duke University Medical Center.
A study published in the Archives of Internal Medicine found a significant 16-point improvement in blood pressure among patients on the DASH diet who participated in aerobic exercise and were encouraged to lose weight.
Patients who just followed the diet showed an 11-point reduction in blood pressure and the control group who continued their typical lifestyles showed a three-point improvement.
"Not only were we surprised by the magnitude of the blood pressure reductions for people on the DASH diet who lost weight and exercised, but we found that they also improved other important cardiovascular biomarkers," said James Blumenthal, PhD, a psychologist at Duke and lead author of the study.
"Participants who just followed the DASH diet also improved, but not as much as those who also exercised and lost weight."
The DASH diet is included in national guidelines for preventing and treating blood pressure. It emphasizes dietary lifestyle changes instead of weight loss through meals comprised of fruits, vegetables, and low fat dairy foods. Whole grains, poultry, fish, and nuts are encouraged over fats, red meats, sweets and sugared beverages.
The new study is the first to evaluate the effect of the DASH diet among people who selected and prepared their own food and, in some cases, did not lose weight.
Blumenthal said this study is similar to a "real world" experience because most past studies provided food for participants from a pre-determined menu.
"The 'pre-hypertensive' and mildly hypertensive individuals included in the study represent a significant percent of our population," Blumenthal said. "If we can intervene and make changes at this critical stage in the process, we may have the opportunity to prevent future heart attacks and strokes."
Participants included 144 people who were overweight or obese, had elevated blood pressure (systolic: 130-159 and diastolic: 85-99) and were not taking medication. They were randomly assigned to one of three groups: the DASH diet alone, the DASH diet in combination with aerobic exercise plus small group sessions about weight loss techniques, or no change in diet and exercise habits.
After four months, people in the exercise and weight management group lost approximately 19 pounds on average while the other two groups lost minimal weight or gained weight.
In addition to blood pressure differences, the research team also observed changes to the structure and function of the heart. People on the DASH diet who lost weight and exercised had decreased artery stiffness and a reduced thickening in the left ventricle of the heart.
"While blood pressure is a marker of disease risk, the other biomarkers we evaluated are consequences of exposure to high blood pressure, which are important independent predictors of cardiovascular morbidly and mortality," Blumenthal said.
After the four month study period, the research team introduced the DASH diet concept to all participants. They are continuing to follow these individuals to monitor the extent to which they embrace the diet and the resulting impact on blood pressure and other disease markers.
The study was funded by the National Heart, Lung, and Blood Institute.
Study co-authors include Michael Babyak, Alan Hinderliter, Lana Watkins, Linda Craighead, Pao-Hwa Lin, Carla Caccia, Julie Johnson, Robert Waugh and Andrew Sherwood.