Managing hypertension with diet, not drugs
Managing hypertension with diet, not drugs
Diet has potential to stop a killer
Roughly 50 million Americans have high blood pressure, a leading cause of heart disease and stroke. Now, a diet developed by the National Heart, Lung and Blood Institute (NHLBI) in Bethesda, MD, may help prevent hypertension in individuals at risk and manage the condition in those who have it.
"We had no idea how long it would take for dietary changes to lower blood pressure. We were amazed to find it took only two weeks on the DASH [Dietary Approaches to Stop Hyper tension] diet to show marked improvement in blood pressure," says Eva Obarzanek, PhD, RD, NHLBI re search nutritionist and DASH study project leader.
The DASH study included 459 adults with systolic blood pressure of less than 160 mm/Hg and diastolic pressures of 80-95 mm/Hg. About half were women and 60% were African Americans, a group that tends to develop hypertension earlier and more often than other ethnic groups.
DASH tested the effects on blood pressure of eating plans, unlike earlier nutrition research, which focused on the effects of a particular nutrient. "This is really a landmark study because we've moved away from studying single nutrients and looked at an entire diet, or eating pattern," Obarzanek says. "Too many of the single nutrient studies have been very inconsistent."
The DASH study divided participants into the following three eating plans:
· a control plan, similar to an average American diet;
· a plan high in fruit and vegetables;
· a "combination" plan, low in saturated fat, total fat, and cholesterol and high in fruits, vegetables, and low-fat dairy foods. (See chart, below.)
During the first three weeks, all participants received the control diet. For the following 11 weeks, participants were randomly placed in one of the three eating plans. Both the fruit and vegetable plan and the combination plan called for eight to 10 daily servings of fruits and vegetables.
"Current dietary guidelines recommend four to five daily servings of fruits and vegetables, and surveys indicate that Americans on average eat about 4.3 servings of fruits and vegetables daily," Obarzanek says. The combination plan also included two to three daily servings of low-fat dairy foods. All three plans included slightly less sodium than the average American diet.
Participants received all of their food through the study program. "This was a feeding study. Participants came into the clinic for one meal a day, either lunch or dinner, and then received all of their food for the next 24 hours," explains Obarzanek. "We had varying caloric diets ranging from 1,600 to 3,100 calories daily depending on factors such as age, sex, height, and weight."
Findings are significantBoth the fruit and vegetable diet and the DASH combination diet reduced blood pressure in study participants. However, the combination diet had the greatest positive effect, Obarzanek says. The combination plan reduced blood pressure by an average of 5.5 mm/Hg for systolic and 3 mm/Hg for diastolic. The plan worked even better for those participants with hypertension, she adds. In hypertensive participants, systolic dropped an average of 11.4 mm/Hg and diastolic 5.5 mm/Hg. All reductions were noted only two weeks after participants started the diet, she says.
A new study is under way to test the relationship among blood pressure, eating patterns, and salt intake. "We want to take the combination DASH diet and see what part sodium plays," Obarzanek says. "We plan to test the diet using three different sodium levels." (The DASH2 study is still accepting new participants. For more information, see box, above right.)
"Our findings are very significant to practitioners," Obarzanek says. "It means that for a practitioner with hypertensive patients, for at least some subsets of patients, diet may effectively control hypertension and eliminate the need for drugs," she says. "Any time you can make dietary changes that have the potential to improve the health of the entire population, it's very exciting. And Ameri cans can be convinced to change their eating hab its. Just look at the grocery store shelves at the wide range of low-cholesterol, low-fat, and fat-free foods!" (For suggestions on helping clients make healthy changes in their diet, see story at right.)
Of course, patients should not stop taking their blood pressure medication without consulting their physicians, Obarzanek cautions. However, the DASH diet may be an alternative to single-drug therapy for patients with Stage I hypertension, she says.
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