African Americans Less Likely to Adhere to DASH Diet

September 19, 2012

September 19, 2012 (Durham, North Carolina) — Greater adherence to the Dietary Approaches to Stop Hypertension (DASH) diet, regardless of weight loss, is associated with larger reductions in blood pressure, research shows. African Americans, however, were less likely than their white counterparts to adhere to the diet, suggesting that "culturally sensitive" dietary strategies might be needed to improve adherence to the DASH diet [1].

The total adherence score, which is a scoring scheme designed to assess adherence to equally weighted food and nutrient components of the DASH diet and ranges from zero to 10 (full adherence), was 4.68 for African Americans and 5.83 for white subjects. Specifically, African Americans were less likely than white individuals to consume fruits and vegetables that make up much of the DASH diet and to decrease total fats and sweets.

"There seems to be a difference in general, but also in specific food groups," Dr Poa-Hwa Lin (Duke University, Durham, NC), one of the researchers involved in the study, told heartwire . "African Americans seem to have a harder time getting to the recommended amount of certain food groups. For example, they were not able to increase fruits and vegetables to the amount that's recommended within the study period. They all improved from baseline, but white participants improved their adherence more than African Americans did. African American individuals improved their adherence to the diet, but just not as much."

On average, African Americans consumed 4.24 servings of vegetables per day compared with 5.28 servings per day consumed by white subjects. Similarly, African American subjects ate just 2.67 servings of fruit per day while white individuals ate 3.07 servings per day, both of which are below the recommendation of four to five servings per day. In contrast, African Americans ate 9.1 servings of sweets per week compared with 5.55 servings among white individuals, and they also ate slightly less dairy.

The study is published online September 19, 2012 in the Journal of the Academy of Nutrition and Dietetics.

DASH Diet

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.

The ENCORE Study

The new analysis is taken from an ancillary study of the Exercise and Nutrition Interventions for Cardiovascular Health (ENCORE) trial, a 16-week randomized clinical trial of diet and exercise that included 144 sedentary, overweight, or obese adults with high blood pressure. Individuals randomized to the DASH diet plus a program of weight management reduced their systolic and diastolic blood pressures 16.1 mm Hg and 9.9 mm Hg, respectively, while those randomized to the DASH diet alone had reductions of 11.2 mm Hg and 7.5 mm Hg. For the control arm who consumed their usual diet, which was characterized by higher intakes of fat, saturated fat, cholesterol, and lower-than-recommended levels of protein, fiber, and essential nutrients, the reductions in systolic and diastolic blood pressure were 3.4 mm Hg and 3.8 mm Hg, respectively.

In terms of adherence to the DASH diet, postintervention assessments of dietary servings yielded a total adherence score of 6.23 and 6.20 among subjects randomized to DASH plus weight management and DASH alone, both of which were significantly higher than the adherence score of 3.66 for those who consumed their usual diet. Not surprisingly, individuals with higher postintervention DASH adherence scores, as well as greater weight loss, had lower systolic blood-pressure levels after treatment. Each two-point increase in the DASH diet adherence score was associated with a 3.4-mm-Hg reduction in systolic blood pressure. This association, however, was not statistically significant after adjustment for weight loss.

In a multivariate regression analysis, baseline adherence scores were positively associated with adherence to the DASH diet at four months. After treatment, African American race was the only predictor of adherence at four months, with no other clinical, demographic, or social variables predicting adherence.

DASH Not Overly Complicated

To heartwire , Lin said that the DASH diet is not a complicated diet, per se, with its components readily available from local supermarkets. Changing behavior, on the other hand, remains the weak link in getting individuals to comply with and adhere to any lifestyle change designed to improve health. Lin noted, however, that research has suggested that African American subjects are slower to change their eating habits than other ethnicities, but they do change. In fact, one of the drawbacks of the present study is that it is just four months long. It is possible that if studied longer, the researchers might have observed improved compliance with the DASH diet.

"The take-home message is that the diet does work and that the more you can adhere to it the better the blood-pressure reduction," said Lin. "That's a fact that we have proven over and over again. Now, when doctors work with their patients, we need to really make them understand, to really help them buy into adopting this diet. That's the first step--patients really need to believe that this diet can work for them."

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