Dr Phillip Mellen

Presenting these discouraging findings here at the American Society of Hypertension 2007 Scientific Sessions, lead investigator Dr Phillip Mellen (Wake Forest University School of Medicine, Winston-Salem, NC) said the dietary quality of hypertensive adults has deteriorated since the DASH diet became incorporated in the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC) guidelines, and there are significant differences in accordance rates by age, ethnicity, and education.

"We appear to be improving, somewhat, with respect to awareness of hypertension and with respect to treatment of hypertension as well," said Mellen. "But these data are consistent with what we're seeing in the broader population, that the dietary patterns are getting worse over time. . . . We might be getting better at medicines but neglecting nonpharmacologic ways to treat hypertension."

The DASH study, first published in 1997, showed that a diet rich in fruits, vegetables, grains, and low-fat dairy products significantly lowers blood pressure, especially in hypertensive patients. Systolic and diastolic blood pressure in hypertensive patients in the DASH trial was lowered 11.4 mm Hg and 5.5 mm Hg, respectively.

Based on these findings, the national guidelines, both the JNC-6 and JNC-7, included the DASH diet among the therapeutic lifestyle changes advocated for all patients with or at risk for high blood pressure, regardless of concomitant antihypertensive drug therapy. In this newest study, Mellen and colleagues sought to determine whether people with hypertension were following the diet and whether the diet of hypertensive Americans improved since the DASH approach was incorporated into the guidelines.

Using data from the 1999-2004 National Health and Nutrition Examination Survey (NHANES), investigators reviewed the self-reported dietary habits of 4386 adults with hypertension and developed a scoring system that reflected intake of nine target nutrients, including total fat, saturated fat, protein, cholesterol, fiber, calcium, magnesium, potassium, and sodium. Individuals meeting at least half of the nine targets were considered accordant with the DASH diet.

Of the more than 4000 surveyed hypertensive adults, just 22% were following the DASH diet. Compared with a NHANES survey period preceding the implementation of the DASH diet into the national guidelines, accordance with the recommended diet was 8% lower in this most recent cohort. Older adults were more likely to follow the diet than those younger than 40 years, and African Americans were 39% less likely to follow the DASH diet than non-Hispanic whites. Education also affected accordance rates, report investigators, with those having more than a high school education 80% more likely to follow the diet. Patients with diabetes were also more likely to follow the recommended eating plan in the DASH diet.

Speculating as to why fewer patients are following the recommendations, Mellen noted that many physicians do not feel adequately trained to implement the DASH diet. More likely, however, is the fact that dietary counseling takes time, and clinicians are still not reimbursed for their counseling labors. "It might be easier to give a prescription than to address root causes," said Mellen.

In addition, fruits, vegetables, and whole grains are up against the aggressive and profit-driven motives of the fast-food industry, and as of yet there are still no large advertising constituencies pushing fruits and vegetables, an industry that typically relies on public-health-oriented messages to spread the word. While the DASH diet has been incorporated into the guidelines, raising awareness is still needed at the population level, said Mellen.

"We live in a free market in which the calorie-dense and nutrient-poor foods are much more profitable," said Mellen, "and that is a major underlying force determining the diet of the population. I think that as we're hearing more and more about the impending consequences of the obesity epidemic, which we really haven't even begun to fully realize, we can't abandon these lifestyle interventions. It calls on us to evaluate whether there are more ways to get this into the population."