Rationale, design, and methods of the dietary approaches to stop hypertension for diabetes (DASH4D) controlled feeding trial.

Diabetes and hypertension frequently coexist, greatly increasing cardiovascular and mortality risk. The optimal dietary strategies for blood pressure (BP) control in people with diabetes remain uncertain. This report details the rationale and design of the Dietary Approaches to Stop Hypertension for Diabetes (DASH4D) trial, a randomized, controlled, crossover feeding study designed to evaluate the effects of the DASH4D dietary pattern and sodium content on BP among adults with type 2 diabetes. The DASH4D dietary pattern was developed by adapting the DASH diet, an effective diet for BP lowering, to maximize efficacy and safety in a diabetes population. The DASH4D trial randomized participants to a sequence of four 5-week feeding periods testing the following diets: 1) DASH4D diet with lower sodium, 2) DASH4D diet with higher sodium, 3) comparison (typical US) diet with lower sodium, and 4) comparison diet with higher sodium (primary contrast: 1 vs. 4). Diets were tailored to meet specific nutrient targets, and calories were adjusted to maintain stable weight. The primary outcome was systolic BP, and the secondary outcome was diastolic BP. Key additional outcomes included measures of glycemia, lipids, proteinuria, and diet acceptability. The study design addressed multiple challenges including conducting controlled feeding in a medically complex population, maximizing dietary adherence, and implementation during the COVID-19 pandemic. This design provides a road map to rigorously evaluate the efficacy of nutritional interventions in people with diabetes, and generates critical evidence to inform guidelines and clinical practice around the optimal dietary strategies to control diabetes and hypertension.