The diet worked especially well for those with high blood pressure, producing reductions similar to those from single-drug therapy. But it also proved effective for those with high normal blood pressure, who are at a substantial risk of developing hypertension.
The blood pressure reductions occurred without changes in weight, or alcohol or sodium consumption.
Results from the "Dietary Approaches to Stop Hypertension" (DASH) trial appear in the April 17, 1997, issue of The New England Journal of Medicine (NEJM). Preliminary results from the trial had been presented at the American Heart Association meeting in November 1996. The NEJM article gives the final results and describes the diet patterns used.
DASH was funded by the National Heart, Lung, and Blood Institute (NHLBI), with additional support by the National Center for Research Resources and the Office of Research on Minority Health. All three are units of the National Institutes of Health.
"High blood pressure affects about one in four Americans, but there have been few dietary guidelines to help prevent or control it," said NHLBI Director Dr. Claude Lenfant. "DASH offers another nutritional approach. If added to other lifestyle recommendations, the DASH diet should help prevent hypertension and may reduce some persons' need for medication to control the condition."
The other lifestyle recommendations are to maintain a healthy weight, choose foods lower in salt and sodium, drink alcohol in moderation (for those who drink), and be physically active.
DASH enrolled 459 adults with systolic blood pressures of less than 160 mm Hg and diastolic pressures of 80-95 mm Hg. Of those, 133 had Stage I hypertension (140-159/90-99 mm Hg) but were not taking a medication for it. About half of the participants were women and 60 percent were African Americans, who tend to develop hypertension earlier and more often than whites.
The trial examined the effect on blood pressure of whole dietary patterns, rather than of individual nutrients. It compared the effects of three diets: a control diet similar in nutrients to what many Americans consume; a diet high in fruits and vegetables; and a "combination" diet low in saturated and total fat, and high in fruits, vegetables, and low fat dairy foods.
Both the fruits and vegetables diet and the combination diet had 8-10 daily servings of fruits and vegetables--about twice the average U.S. consumption. The combination diet also had 2-3 daily servings of predominantly low fat dairy foods--about twice the current U.S. consumption and within the Dietary Guidelines for Americans.
All three diets had about 3 grams of sodium daily--slightly below the average U.S. consumption--and all included fresh, frozen, canned, and dried foods. None of the diets was vegetarian or used specialty foods containing fat substitutes.
At the end of 8 weeks, the combination diet produced the largest reductions in blood pressures. Overall, it reduced blood pressure by an average of 5.5 mm Hg for systolic and an average of 3.0 mm Hg for diastolic. For those with hypertension, it reduced blood pressure by an average of 11.4 mm Hg for systolic and an average of 5.5 mm Hg for diastolic.
In comparison, after 8 weeks, the fruits and vegetables diet reduced blood pressure for all participants by 2.8 mm Hg for systolic and 1.1 mm Hg for diastolic, and for those with hypertension by 7.2 mm Hg for systolic and 2.8 mm Hg for diastolic.
Blood pressure reductions occurred in men and women, and in whites and minorities. Further, the blood pressure reductions happened quickly--within 2 weeks after starting the diet--and were maintained for the rest of the 8 weeks on the diet.
The DASH investigators believe the combination diet can help prevent high blood pressure and may be an alternative to single-drug therapy in persons with Stage I hypertension. However, they stress that patients should not stop taking a high blood pressure medication without first consulting their physician.
The investigators estimate that if Americans followed the DASH diet and had the degree of blood pressure reductions seen in the trial, there would be about 15 percent less coronary heart disease and 27 percent fewer strokes in the U.S.
DASH centers and principal investigators are: Dr. Thomas J. Moore of Brigham and Women's Hospital and Harvard Medical School in Boston, MA, who served as trial chairman; Dr. Lawrence J. Appel of The Johns Hopkins University in Baltimore, MD; Dr. George A. Bray of the Pennington Biomedical Research Center in Baton Rouge, LA; Dr. Laura P. Svetkey of Duke University Medical Center in Durham, NC. The DASH Coordinating Center principal investigator is Dr. Thomas M. Vogt and the project director is Dr. William M. Vollmer, both of the Kaiser Permanente Center for Health Research in Portland, OR.
Dr. Eva Obarzanek, DASH project officer at NHLBI, is available for interviews. To arrange an interview with her or a DASH principal investigator, call the NHLBI Communications Office at 301-496-4236. The DASH diet also is available online at http://dash.bwh.harvard.edu.
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NHLBI press releases, fact sheets, and other materials are available online at the following website: http://www.nhlbi.nih.gov/nhlbi/nhlbi.htm