Fewer Carbs Boost DASH Diet's Heart Benefits

Replacing carbohydrates with protein or monosaturated fats checked blood pressure

TUESDAY, Nov. 15, 2005 (HealthDay News) -- Two carbohydrate-reduced versions of the government's Dietary Approaches to Stop Hypertension (DASH) diet have a beneficial effect on blood pressure, cholesterol levels and long-term cardiovascular risk, researchers report.

The new diet shifts about 10 percent of calories from carbohydrates to either protein-rich foods or to monounsaturated fats such as olive or canola oil.

"This diet should be a frontrunner," said Dr. Frank Sacks, one of the authors of the study and a professor of medicine and nutrition at Brigham and Women's Hospital and Harvard in Boston. "It improved the whole cardiovascular risk spectrum. A lot of patients are tough to control with the medications we have. Patients might not even need drugs if they go on the diet."

"This is a modified version of the old diet," Sacks explained. "The DASH diet was a real breakthrough for lowering blood pressure and we changed it. We reduced the carbohydrate content and replaced it with unsaturated fat or protein, and it lowered blood pressure more and improved lipids, and overall cardiovascular risk goes down."

He called the new regimens "an improvement over something that's already good."

Another expert agreed that the two new versions of the DASH diet, as well as the original DASH, which was developed by the National Heart, Lung and Blood Institute, should work.

"These are just alternative versions," said Dr. Jay Skyler, a professor of medicine and associate director of the diabetes research institute at the University of Miami School of Medicine. "To me, whether you get a little bit more lowering with one or another diet than the other matters less than the fact that you ought to stick to any one of these three. They're all better than the conventional diet that these people were on."

The findings were presented Tuesday at the American Heart Association's annual meeting in Dallas, and also appear in the Nov. 16 issue of the Journal of the American Medical Association.

The DASH diet has been considered the gold standard of heart-healthy nutrition since it was pioneered in the mid-1990s. The original diet was carbohydrate-rich, emphasizing fruits, vegetables and low-fat dairy products. Unfortunately, in addition to lowering "bad" or LDL cholesterol, the regimen also reduced "good" or HDL cholesterol, and had no effect on blood fats called triglycerides.

To help make the regimen even healthier, the same researchers updated the diet and compared the two new versions with the old one.

For this study, 164 adults aged 30 and older with elevated blood pressure were assigned to one of three diets: one in which carbohydrates represented 55 percent of calories (close to the original DASH diet); one that shifted 10 percent of carbohydrate calories to protein (about two-thirds from plant sources and the rest from chicken and egg whites); and one that shifted 10 percent of calories to unsaturated fat, mostly olive or canola oils. About half of the participants were black, a group at especially high risk of developing hypertension.

All of the diets lowered participants' blood pressure, LDL cholesterol and estimated coronary heart disease risk, the researchers report, and the protein and unsaturated fat diets showed even better improvements.

Compared to the old diet, the enhanced-protein version decreased blood pressure by an extra 1.4 mm Hg overall and by an extra 3.5 mm Hg among those with hypertension; it decreased LDL cholesterol by an additional 3.3 mg/dL and triglycerides by 15.7 mg/dL.

Compared to the original DASH diet, the unsaturated fat-rich version decreased systolic blood pressure by an additional 1.3 mm Hg overall and by 2.9 mm Hg among those with hypertension; it increased HDL cholesterol by an extra 1.1 mg/dL and lowered triglycerides by 9.6 mg/dL.

Both the protein and unsaturated fat diets reduced heart disease risk more than the DASH diet.

Breakfast was similar in all three diets and included fresh fruit, fruit juice, whole grain cereal and skim milk. Lunches and dinners were varied. A typical protein-diet dinner might include one ounce of raisins and cherries, where the carbohydrate dinner included a peppermint patty.

How practical are the improvements? All the study participants were given their meals. In the real world, people will have to prepare these meals themselves.

"Would people be able to stick to any of these as effectively when they're doing it at home? That's the unknown thing here," Skyler said. "I think whatever people will stick to and are happy with will work. I would be happy with the results of any of these three."

Sacks said his team was working on making the diet easy to use. "Our next project is to work on foods and menus and things that people can use, to give people more specific guidance," he said. "Hopefully that'll be out in a couple or three months. We feel a sense of urgency to get some real practical stuff out like we did with the DASH diet."

An accompanying editorial also emphasized the need for lifestyle changes such as more exercise, in addition to diet, to keep blood pressure low.

A second study, also presented Tuesday at the American Heart Association meeting, found that men and women who reduced their sodium intake lowered their risk of cardiovascular disease or death by 26 percent.

More information

For more on the original DASH diet, head to the National Heart, Lung, and Blood Institute.

SOURCES: Frank Sacks, M.D., professor, medicine and nutrition, Brigham and Women's Hospital and Harvard, Boston; Jay Skyler, M.D., professor, medicine, and associate director, diabetes research institute, University of Miami School of Medicine; Nov. 15, 2005, presentation, American Heart Association annual meeting, Dallas; Nov. 16, 2005, Journal of the American Medical Association
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