Diet, Exercise Together Effective in Controlling High Blood Pressure
DURHAM, N.C. -- New research suggests that an overhaul of dietary and fitness habits to help prevent or control high blood pressure is feasible with proper coaching, contrary to the theory that too many changes would be overwhelming and ineffective for most people. The best results in the study were achieved when weight loss, salt restriction and exercise were paired with the DASH (Dietary Approaches to Stop Hypertension) diet, which is rich in fruits, vegetables and low fat dairy products.
The results of the study, conducted at Duke University Medical Center, Johns Hopkins, Pennington Biomedical Research Center, and the Center for Health Research, were published in the April 23, 2003, issue of the Journal of the American Medical Association. The study, called PREMIER, is funded by the National Heart, Lung and Blood Institute.
Current national recommendations for lowering blood pressure include weight loss, reduced sodium intake, increased physical activity, limited alcohol consumption and DASH diet. The DASH diet increases fruit, vegetable and low-fat dairy consumption, while limiting fats, red meat, sweets and beverages containing sugar. In a study by some of these researchers and others published in 1997 in the New England Journal of Medicine, the DASH diet lowered blood pressure rates without medication, weight loss or reduction of salt intake.
A subsequent study by the same investigators published in 2001 in the New England Journal of Medicine showed that DASH with reduced sodium intake was even more effective than DASH alone. However, the DASH studies were highly controlled nutrition studies in which all foods were provided and not prepared by the participants.
"No previous study has tested the ability of people to adopt DASH on their own or its effectiveness in the 'real' world. And no previous study has tested all the other recommendations for lowering blood pressure, either with or without DASH, as an "all-in-one' intervention," said Laura Svetkey, M.D., director of Duke Hypertension Center, director of clinical research at the Stedman Nutrition Center, and principal investigator in the PREMIER trial.
The PREMIER trial enrolled 810 generally healthy people with above-optimal blood pressure, including those with stage one hypertension (systolic BP 140-159 mmHg and/or diastolic BP 90-95 mmHg). The participants were randomized into one of three groups
--"Established" intervention including traditional diet and exercise guidance, and
--"Established Plus DASH," which implemented the same traditional recommendations plus the DASH diet.
None of the participants took medications for hypertension. Those in the "Advice Only" group each met with a registered dietitian at the beginning of the trial to discuss recommendations for weight control, reduced sodium intake, physical activity and the DASH diet for lowering blood pressure. The dietitian gave participants printed educational materials, but counseling on behavior change strategies was not provided.
Participants in both the "Established" and "Established Plus DASH" intervention groups set goals to lose 15 pounds within six months, increase physical activity, lower sodium intake and limit alcohol to one or two drinks per day. The Established Plus DASH group also set goals to increase fruit, vegetable and low-fat dairy intake and reduce saturated fat and total fat. The Established group was given no instructions on the DASH diet. During the initial six months of the trial, both groups met frequently to reinforce behavior modification.
During the first six months of the trial, all participants in both the Established and Established Plus DASH groups significantly lowered their blood pressures in comparison to the Advice Only group. The Established Plus DASH group had the lowest prevalence of hypertension -- cutting group members' risk of developing hypertension by 53 percent compared to the Advice Only group.
"At six months, we had 19 participants in the Advice Only group who had to begin anti-hypertensive medication to control their blood pressures, compared to only two in the Established Group and five in the Established Plus DASH group," said Svetkey. "And both behavior modification groups had a significant number of the participants reach their optimum blood pressure."
All groups had an overall reduction in weight. In the Established Plus DASH group, 34.3 percent lost 15 pounds or more, while in the Established group, 28.6 percent lost 15 pounds or more. The Advice Only group had only 6.2 percent lose 15 pounds or more.
When participants took a treadmill exercise test, the tests showed fitness increased significantly in both the Established and Established Plus DASH groups. The Established Plus DASH group achieved other lifestyle goals: One-third of these participants reached their goal of consuming nine or more servings of fruits and vegetables every day. Only 6 percent of participants in the other two groups reached this marker.
"Because we have seen how the DASH diet can significantly lower blood pressures, we expected to see a greater reduction in blood pressure rates in the Established Plus DASH than in the Established group, but they were about the same overall," said Svetkey. "While participants on average increased their fruit and vegetable consumption from 4.8 to 7.8 servings per day, many still did not reach the optimum goal of nine to 12 servings per day. But those on the DASH diet also benefited from other potential benefits: prevention of osteoporosis from the high calcium content, prevention of some cancers from the high fruit and vegetable content, and the prevention of cardiovascular disease from the low fat content."
Although the results for the Advice Only group were not as striking as the other two, this group did better in losing weight and decreasing sodium intake than expected. Svetkey said this could be because motivated people usually sign on to participate in clinical trials, and may produce better results than could be expected in the average population. "You also have to factor in that even the limited amount of advice and counseling this group received was more than most people get in clinical practice, so that contributed as well," she said.
The long-term goal of the study, said Svetkey, is to follow all the participants an additional 12 months (18 months total) to determine whether the participants can stick with the diet and exercise, and monitor blood pressure control. Also, the next phase in this series of research will focus on weight loss -- specifically on how to help people lose weight and keep the weight off long-term. This new study, which is also funded by the National Institutes of Health, will begin enrolling participants in May 2003.