Healthy Diet Plus Less Salt can Eliminate Need for High Blood Pressure Medications

Duke University Medical Center
Wednesday, 17 May 2000

Eating a healthy diet called "DASH," together with restricting salt intake, can reduce blood pressure to such a degree that it may eliminate the need for medication in some people, according to a follow-up study on "Dietary Approaches to Stop Hypertension."

Investigators at five research institutions nationwide had earlier found that the DASH diet -- rich in fruits, vegetables and low-fat dairy foods but not necessarily low in salt -- reduced blood pressure by an average of 5.5 points among all subjects, without requiring them to lose weight or restrict salt.

When subjects combined salt reduction (1500 mg per day or less) with the DASH diet, their blood pressure dropped by an average of 9 points overall -- a reduction equivalent to that of using medications, the current study found.

The benefits were even more striking for people who had the greatest degree of hypertension: among this group, the DASH diet and a very low sodium intake reduced their blood pressure by 12 points.

Results of the study, funded by the National Heart, Lung and Blood Institute, are being presented May 18 at the annual meeting of the American Society of Hypertension in New York. Sites participating in the study were Duke University Medical Center, Brigham and Women's Hospital, Johns Hopkins University, Pennington Biomedical Research Center and Kaiser Permanente Center for Health Research, which coordinated the data.

"These are extremely compelling results because they demonstrate an effective, non-medical treatment for people with hypertension as well as a preventive measure for the tens of millions of Americans on the verge of becoming hypertensive," said Dr. Laura Svetkey, director of the Duke Hypertension Center and a co-author of the study.

"Moreover, the diet is feasible because it is less restrictive than most, allowing people to eat some of their favorite foods like meat, unsalted peanuts and cookies, in moderation."

The researchers say their findings are especially important because they lay to rest

the lingering controversy over whether or not salt reduction benefits people who don't have high blood pressure, and what the optimal level of salt reduction is.

The study found unequivocally that salt reduction and DASH, combined and independently, lowered blood pressure in all subjects -- healthy and hypertensive, men and women, black and white, young and old.

In fact, the less salt the subjects ate, the lower their blood pressure dropped. Subjects eating the DASH diet with the lowest sodium content, just 1500 mg per day or half the current recommended daily allowance, showed a greater drop in blood pressure than the intermediate- and high-sodium groups.

But even the control subjects, who ate a typical American diet high in fat but lacking in fruits and vegetables, lowered their blood pressure to some degree when they were on the reduced-salt portion of the control diet, the study found.

"These results should settle the lingering controversy on how sodium reduction affects blood pressure," Svetkey said. "It is clear from our clinical trial -- a large, well-controlled study with a diverse population and a tightly monitored feeding regimen -- that restricting salt is a very effective way of lowering blood pressure in people who don't already have high blood pressure, and it works even better among people who do have it."

In fact, the authors suggest that the medical community should more aggressively promote reducing salt below the 2400 mg currently recommended, given the pervasiveness of hypertension -- 140/90 or higher -- among the general population. Svetkey said that high blood pressure affects one in four adults and is a leading cause of heart disease, stroke and kidney failure in the United States. Moreover, blood pressure tends to increase with age, and the DASH/low-sodium diet could stave off its rise.

But getting Americans to lower their salt intake even beyond the current recommended level will prove difficult without the food industry's support, the authors say. The bulk of dietary salt is already in the foods commonly purchased off the grocery store shelf, such as bread, cheese and cereal, not to mention prepared foods like canned soups and boxed dinners, Svetkey said.

"The food industry has to partner with the public health community in order to make more healthy food choices available to Americans, and then the population at large can learn to reduce their salt intake," Svetkey said. "People think if they remove salt from food, it won't taste as good. But it's fairly easy to add spices that are just as flavorful as salt."

Even in the absence of reducing salt, the DASH diet would benefit millions of Americans because it is a healthy approach to eating that could help prevent heart disease, cancer, diabetes and osteoporosis, among other diseases.

Of particular benefit, she said, is that DASH does not require people to lose weight, a mainstay of hypertension treatment that is effective but extremely difficult to maintain. Statistics show that fewer than five percent of adults who lose weight are able to keep it of for five years, no matter what weight-loss method they use, and 62 percent of them regain all of their lost weight within five years.

Svetkey said DASH is less restrictive than other "diets" because it doesn't require the same degree of deprivation. Although it is a reduced-fat diet, subjects can eat unsalted peanuts, cookies, meats and other high-calorie foods in moderation. It also includes four to five daily servings of fruits and four to five daily servings of vegetables, about twice the average American consumption of fruits and vegetables, as well as three daily servings of low-fat dairy foods.

All foods were bought off the grocery store shelf and required no special preparation. The participants were not allowed to lose weight so that researchers could study the effects of the diet and salt restriction independent of other factors.

The 412 participants at the four study sites all ate the control diet -- typical American fare high in fat and sodium -- for a period of two weeks. Then they were randomly assigned to either continue on the control diet or to eat the DASH diet. Within the DASH and control diets, all subjects rotated through a high-sodium, intermediate-sodium and low-sodium phase for a period of 30 days for each sodium level. Blood tests and urinalyses were taken periodically to ensure that participants were adhering to the appropriate diet.

For more information, or to contact Duke University Medical Center, see their website at: www.mc.duke.edu