U.S News and World Report recently ranked the DASH diet as the No.1 Healthiest Diet. Today I partly explain why.
The Dietary Approaches to Stop Hypertension (DASH) diet has been shown to lower blood pressure. Another study associated a DASH-style diet with lower incidence of heart attack and stroke.
The DASH diet is low in total and saturated fats and cholesterol, moderate in low-fat dairy products, high in fruits and vegetables, low in salt, low in sweetened beverages, moderate in whole grains, and low in animal protein but has substantial amounts of plant protein from nuts and legumes.
The DASH diet was designed as a healthy way of eating, not a weight-loss diet. It is promoted by the National Heart, Lung, and Blood Institute for the prevention and treatment of high blood pressure. It is also included as an example of a healthy diet in the 2005 Dietary Guidelines for Americans. Yet many people still have never heard of it.
Researchers affiliated with multiple Boston and Atlanta institutions looked at the participants in the massive Nurses Health Study. 88,517 middle-aged women free of stroke, diabetes, and coronary heart disease were followed between 1980 to 2004. They filled out food frequency questionnaires designed to assess average food intake over the preceding year. The researchers constructed a DASH diet score and graded all the study participants in terms of adherence or conformity to the ideal DASH diet.
Over the course of the study, there were 2129 cases of nonfatal heart attack, 976 deaths from coronary heart disease, and 2317 strokes. (If you read the original study, please note that some numerical errors were corrected in a later journal issue.)
Women with the highest adherence to the DASH Diet had 24% lower risk for coronary heart disease, compared with the women who had the lowest conformity. Again comparing the same two groups for stroke, the high-adherence women had 18% less incidence of stroke. There were clear trends for less coronary heart disease and stroke as adherence to the DASH diet increased.
Blood samples were analyzed for a subset of participants. Higher DASH compliance was significantly associated with lower plasma levels of interleukin-6 and C-reactive protein. These are markers for the inflammation felt to underlie atherosclerosis and cardiovascular disease. You want to avoid high inflammatory markers. The DASH diet scores in this study were not associated with serum lipid changes, although other DASH studies found lower LDL cholesterol and an undesirable reduction in HDL cholesterol.
The researchers examined causes of death in participants, yet did not report any association – positive, negative, or neutral – with DASH score. I wonder why? It’s possible that higher DASH scores were associated with higher overall death rates even though they had fewer heart attacks and strokes. I imagine they also had access to cancer death statistics. Why no mention? Academicians are under pressure to publish research reports. Are they saving the mortality and cancer data for future articles? Abscence of all-cause mortality numbers is a major weakness of this study.
The DASH diet is similar in composition to the traditional Mediterranean diet. The main differences are that the Mediterranean diet ignores salt intake, allows wine and other alcohol, and places more emphasis on olive oil and whole grains. The Mediterranean diet has numerous supportive studies showing prolonged lifespan and less chronic disease: fewer heart attacks and strokes, less cancer, less dementia. And very recently the Mediterranean diet was associated with a lower incidence of type 2 diabetes mellitus.
Steve Parker, M.D.
Your Guide to Lowering Your Blood Pressure with DASH, from the National Heart, Lung, and Blood Institute