Five Plus Nuts and Beans Study
Elevated blood pressure is an extraordinarily common and important risk factor for cardiovascular disease and stroke, particularly among African Americans. Although pharmacological treatment of hypertension substantially lowers risk for cardiovascular complications, recommendations for adoption of the DASH diet (Dietary Approaches to Stop Hypertension) are recognized as an integral part of medical management. However suboptimal diets, in part, contribute to health disparities in blood pressure control.
African-American race and low income are strongly associated with unhealthy food intake. While unhealthy diets have many social determinants (e.g., educational attainment, literacy, income, insurance status), there is a markedly lower availability of components of the DASH diet-recommended foods (such as fresh fruits and vegetables, skim milk and whole grain foods) in predominantly African-American and lower-income neighborhoods compared with Caucasian and higher-income neighborhoods.
The mechanism by which unhealthy dietary consumption patterns lead to hypertension is, in part, due to resultant deficiencies in potassium, magnesium and vitamin C (micronutrients with independent blood pressure-lowering effects). Even moderate potassium deficiencies are associated with increased blood pressure and salt sensitivity. Furthermore, use of thiazide-based antihypertensive therapy, which is otherwise highly effective as an antihypertensive agent, worsens deficiencies (increased urinary excretion). Inadequate intake and/or accelerated loss of these micronutrients not only affects blood pressure control, but has been directly linked to development of glucose intolerance (potassium and magnesium) and hyperuricemia (vitamin C).
Strategies are needed to improve adherence to dietary recommendations and reverse micronutrient deficiencies in hypertensive African-American adults through tailored dietary advice or use of nutritional supplements.
In this study, we will test the Overall Hypothesis that: In African-American adults on stable doses of antihypertensive medications or at risk for hypertension, a clinic-based dietitian-delivered intervention for adoption of the DASH diet (tailored to neighborhood stores used by individual patients) is effective at lowering blood pressure and improves cardiovascular disease risk factors (reduce fasting glucose, insulin, and uric acid levels).
Specific Aim 1: Test the hypothesis that delivery of nutritional advice to adopt the DASH diet, tailored to choices and availability of foods from local neighborhood stores relevant to individual patients, will lower blood pressure.
Specific Aim 2: Test the hypothesis that the tailored DASH diet advice differs from minimum DASH advise and non-guided shopping advice.
Specific Aim 3: Conduct exploratory analyses related to: a) effects of the interventions in subgroups defined by gender, age, and other baseline variables; and b) effects of potential mediator variables, such as self-monitoring, and type of antihypertensive medication.
Specific Aim 4: Disseminate the results of the trial through shared resources.