January 1, 2008
Doug Brunk
Women who followed the Dietary Approaches to Stop Hypertension diet had significant risk reductions of coronary heart disease and stroke, results from a cohort of participants in the ongoing Nurses Health Study showed.
Previous studies have shown that the diet—heavy in fruits and vegetables—lowers blood pressure and blood lipids, but this marks the first time benefit on a disease state has been demonstrated.
“It's one thing if your blood pressure or cholesterol goes down, but it does not automatically translate to a reduction of disease risk,” lead study author Teresa Fung, Sc.D., said in an interview after the work was presented at the annual scientific sessions of the American Heart Association. “In this study I wanted to see if the diet is related to reducing the disease.”
Developed by researchers funded by the National Heart, Lung, and Blood Institute in the 1990s, the Dietary Approaches to Stop Hypertension (DASH) diet is low in cholesterol and sodium and contains no more than 30% of calories from fat. It emphasizes fruits, vegetables, and fat-free or low-fat dairy products.
Dr. Fung and her associates evaluated 88,415 women from the Nurses Health Study who were aged 34–59 years in 1980 and had no history of cardiovascular disease or diabetes. The researchers used a questionnaire to assess the women's diet seven times over 24 years of follow-up and used medical records to tabulate their incidence of cardiovascular disease and stroke.
In an effort to measure the women's adherence to the DASH diet, the researchers created a DASH score based on their consumption of eight foods and nutrients: fruits, vegetables, whole grains, nuts and legumes, low-fat dairy, red and processed meat, sweetened beverages, and sodium.
Patients were divided into quintiles on the basis of how closely they followed the diet, with quintile 1 being poorly followed (the bottom 20%) and quintile 5 being well followed (the top 20%). Cox proportional hazard analysis was used to adjust for potential confounders such as age, smoking, family history of coronary heart disease (CHD) and stroke, and level of physical activity.
Over the 24-year follow-up, there were 1,876 cases of nonfatal myocardial infarction, 883 deaths due to coronary heart disease, and 2,317 strokes. The researchers observed significantly lower risks of CHD and stroke when they compared quintile 5 with quintile 1. (See box.)
“This is more evidence to promote this diet,” said Dr. Fung, associate professor of nutrition at Simmons College, Boston. She said she was surprised that the magnitude of effect was greater for CHD than for stroke.
The researchers also observed that the risk reduction for stroke was much stronger in women who had a history of hypertension at baseline, compared with those who did not. “The message in that is, even if someone is hypertensive, it's not the end of the world,” Dr. Fung said. “Controlling hypertension by medication or other means is extremely important. You can gain risk reduction if you follow the [DASH] diet. A typical adult should be eating 9 servings of fruits and vegetables combined per day, which is a lot, because the average American consumes between 3.5–4 servings per day. That is not so easy.”
The study was funded by the National Institutes of Health.
