DASH4D Main Trial:
In persons with and without diabetes, elevated blood pressure (BP) is the leading cause of stroke and a major risk factor for other cardiovascular diseases, including coronary heart disease and heart failure. Strategies that effectively lower BP include drug therapy and lifestyle modification. Lifestyle modifications, particularly dietary approaches, have been shown to lower BP in persons without diabetes. However, there is a striking dearth of evidence on BP-lowering, lifestyle modifications, other than weight loss, in persons with diabetes. The DASH4D trial is designed to provide this evidence.
The DASH4D trial builds upon the investigators' experience in four NIH-sponsored feeding studies (DASH, DASH-Sodium, OmniHeart, and OmniCarb). The trial will enroll approximately 100 adults with Type 2 diabetes, systolic BP 120-159 mmHg, and diastolic BP \<100 mmHg, to determine the effects, alone and combined, of (a) the DASH4D diet (a DASH-style diet modified for people with diabetes) vs. comparison diet (typical of what many Americans with diabetes eat) and (b) lower sodium intake vs. higher sodium intake on BP.
The core design is a four-period, single-site, crossover feeding study with 5-week periods. Participants are fed each of four diets, presented in random order:
1. DASH4D diet with lower sodium
2. DASH4D diet with higher sodium
3. comparison diet with lower sodium
4. comparison diet with higher sodium.
The primary contrast of interest is the DASH4D diet with lower sodium vs. the comparison diet with higher sodium.
The DASH4D diet is similar to the original DASH diet, but is lower in carbohydrates and higher in unsaturated fat than the original DASH diet, and therefore, is more consistent with dietary recommendations for persons with diabetes than the original DASH diet. The comparison diet reflects what many persons with diabetes currently consume. The lower sodium intake of approximately 1500 mg/day (at 2000 kcal) has been shown to lower BP in persons without diabetes, and has been recommended in some dietary guidelines. The higher sodium intake of approximately 3700 mg/day (at 2000 kcal) is based on estimated average intake in the US.
Outcomes are measured at the end of each feeding period. The primary outcome is end-of-period, office-based systolic BP. Other outcomes are diastolic BP, measures of glycemia, plasma lipid risk factors, patient symptoms, and estimated cardiovascular disease risk.
Similar to the investigators' prior feeding studies, the investigators expect that the results of the DASH4D trial will be immediately applicable to public health and clinical guidelines and will influence nutrition policy. Furthermore, the trial will provide a rigorous platform to assess the impact of diet and sodium intake on a diverse array of other outcomes in persons with Type 2 diabetes.
DASH4D CONTINUOUS GLUCOSE MONITORING (CGM) ANCILLARY STUDY:
Continuous glucose monitoring (CGM) systems are novel technologies recommended for assessing real-time glucose patterns, biochemical hypoglycemia, and glycemic variability. The DASH4D-CGM ancillary study will offer CGM to all participants in the DASH4D trial during a screening visit and during the two weeks at the end of each of four feeding periods.
CGM outcomes will be based on CGM data captured from week 3 to week 5 (up to 14 days) of each 5-week feeding period. Per current analytic recommendations, CGM outcomes will be generated using all available CGM data for each feeding period. The primary CGM outcomes are mean glucose, time-in-range (percentage of time glucose is between 70 and 180 mg/dL), and coefficient of variation. These outcomes were selected based on clinical guidelines and recommendations from a consensus statement on CGM endpoints for clinical trials.
We hypothesized that salt would have no effect on glucose. Therefore, we plan to combine data from the lower and higher sodium feeding periods for each diet to increase statistical power. Our primary aim is to examine the average difference in mean glucose, time-in-range, and coefficient of variation between the DASH4D and comparison diets.
