Women who ate foods that matched a well-known diet for reducing high blood pressure had a lower risk of heart disease and stroke than women whose diets didn't come as close, a new study reports.
The Dietary Approaches to Stop Hypertension, better known as the DASH diet, promotes eating foods low in cholesterol and sodium by emphasizing fruits and vegetables and minimizing red meat and fat. Following the diet pushes blood pressure down both for people who have hypertension and for people with normal blood pressure, research has shown. It also cuts cholesterol, according to other research.
But no studies had gone one step beyond those risk factors to see whether the diet made a difference in the incidence of heart disease and stroke in healthy people, according to Teresa T. Fung of Simmons College and the Harvard School of Public Health.
Her study, appearing in the Archives of Internal Medicine, tracked what healthy women in the Nurses' Health Study ate, based on their responses to questionnaires, and assessed how well their diets approximated the DASH guidelines. The study was large, including more than 88,000 nurses who had no history of cardiovascular disease or diabetes and were between the ages of 34 and 59 when the study began in 1980.
After 24 years, the women who most closely followed the DASH diet had a 24 percent lower risk of heart disease than the women whose diets were farthest from the DASH model. Those who ate DASH-like diets had an 18 percent lower risk of stroke than the least-DASH-like group.
"This is a diet that is worth following for just about anybody," Fung said. "Although it's famous for being able to reduce blood pressure, I don't think people should wait until they get high blood pressure to get onto this diet."
She noted in an interview that if a diet or other preventive measure reduces a risk factor for a disease, that doesn't automatically mean the disease itself will be reduced. "There have been disappointments in the past."
One of those came from the Women's Health Initiative. The huge trial tested whether hormone therapy, which had appeared to reduce risk factors for heart disease, really made a difference in disease development. The study was halted early when it became clear that hormones not only did not protect the women's hearts but also increased their risk of heart attacks, strokes, blood clots, and breast cancer.
For that reason, the DASH trial results were a relief, Fung said. She would also like to see whether the diet reduces the risk of other diseases such as diabetes and perhaps certain cancers. But she said people shouldn't wait to take advantage of its benefits.
Dr. Thomas J. Moore of Boston University Medical Center, who led the original studies of the DASH diet, said Fung's research is the first he knows of that relates eating foods found in the diet to actual disease outcomes instead of surrogate endpoints. But he pointed out, as Fung and her colleagues note in the paper, that it was not a gold-standard controlled trial in which participants were randomly assigned to a DASH or non-DASH group.
"The problem with these types of epidemiology studies is that one can never be sure that what you are looking at is cause and effect," he said in an e-mail interview. "Women who choose to eat a healthy, DASH-like diet may be doing other things that contribute to health."
The authors attempted to adjust for these factors, however, Moore said, and a more stringent trial would take many years and thousands of subject to accomplish.
"A well-done epidemiological study like this may be the best we can do," he said.
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