DURHAM, N.C. -- A dietary regimen that lowers blood pressure without weight loss or salt restriction appears to work best for blacks, the population that suffers most from hypertension, researchers report.
In a follow-up study that researchers say has broad public health implications, doctors at Duke University Medical Center and four other sites nationwide showed that simply eating more fruits, vegetables and low-fat dairy products significantly lowered blood pressure in nearly all subjects, but particularly in African Americans with hypertension.
The diet lowered their blood pressure an average of 13 points, the same response seen with medications, said Dr. Laura Svetkey, director of the Duke Hypertension Center and lead author of the study. Whites with hypertension showed an average six-point drop in blood pressure, a reduction still considered to be a very significant achievement through a dietary measure alone. Subjects with blood pressure at the higher end of normal also benefited from the diet, but to a lesser degree, suggesting that the higher your blood pressure, the better you will respond to the diet.
"The implication is that people with severe hypertension might benefit even more from the DASH diet than the group we studied," Svetkey said. Subjects in the current study had mild hypertension or blood pressure at the high end of normal.
Results of the study, funded by the National Heart, Lung and Blood Institute (NHLBI), are published in the Feb. 8 issue of the Archives of Internal Medicine.
Svetkey said the reason for the difference in response between blacks and whites is unknown, as is the mechanism through which the diet is lowering blood pressure. But regardless of its mode of action, Svetkey said any treatment that provides distinct benefits to African Americans is particularly welcome, since this group suffers disproportionately from hypertension.
"Clearly, there are environmental and biologic forces at work which intertwine to create a unique set of circumstances in African Americans that predispose them to developing hypertension and its resulting complications," Svetkey said. "While we haven't identified all the elements that contribute to this phenomenon, we now have a simple, inexpensive and highly effective treatment to combat what has become a major public health threat."
High blood pressure affects one in four adults and is the leading cause of heart disease, stroke, and kidney failure in the United States. Blacks suffer from hypertension in even greater numbers, developing the condition earlier in life and with far more dire medical consequences.
Current treatments for hypertension include medication, weight loss and salt restriction. But all have their drawbacks. Medications have unwanted side effects and weight loss is difficult to achieve and even harder to maintain, said Svetkey. Reducing salt intake is typically a struggle, given the high levels of sodium present in many prepared foods and restaurant meals.
"The DASH diet is quite novel because it doesn't require the same degree of deprivation as do current dietary treatments," Svetkey said. "Instead, they'll be adding healthier foods, which should make be easier for people to maintain on a long-term basis."
The DASH diet -- dietary approaches to stop hypertension -- is the first new treatment to be proven effective in at least a decade, Svetkey said. The current study and previously reported results published last April in the New England Journal of Medicine show that DASH worked quickly, within two weeks, and it worked in nearly everyone who tried it, regardless of their initial blood pressure: men and women, blacks and whites, young and old, thin and overweight, rich or poor, sedentary or active.
The DASH diet is a reduced-fat regimen that includes four to five daily servings of fruits and four to five daily servings of vegetables, about twice the average American consumption of these foods. It also includes three daily servings of low-fat dairy foods. Despite its healthful fare, the diet also includes meats, nuts, cookies and other high-calorie foods, but in moderation.
The DASH diet was compared against two others for a period of 11 weeks: a typical American diet high in fat and low in fruits and vegetables; or a typical American diet with added fruits and vegetables. The latter diet also reduced blood pressure in most participants, but to a lesser degree than the DASH diet. The typical American diet did not lower blood pressure at all.
The Duke study site enrolled 129 participants out of a total 459 in all the sites combined. All participants had either mild hypertension, characterized as ranging from 140 to 160 over 90 to 95, or high-normal blood pressure, but none was on medication to treat high blood pressure. Half the participants were men and half were women, and two thirds were African American.
Journal
Archives of Internal Medicine