A modified version of a diet known to lower blood pressure is also effective at lowering glucose in adults with type 2 diabetes, according to a clinical trial led by researchers at the Johns Hopkins Bloomberg School of Public Health.
The study builds on the DASH diet—Dietary Approaches to Stop Hypertension—developed in the mid-1990s by an interdisciplinary team of researchers supported by National Institutes of Health funding to address high blood pressure in the general population. The DASH diet emphasizes fruits, vegetables, and low-fat dairy products, and is low in saturated fat and cholesterol.
To understand the DASH diet's impacts in patients with diabetes, a team led by Johns Hopkins researchers modified the diet for people with type 2 diabetes. The DASH for Diabetes—DASH4D—diet is similar to the DASH diet but lower in carbohydrates and higher in unsaturated fats. The research team also reduced potassium levels in the DASH4D diet to improve safety for individuals with chronic kidney disease.
A new study , published online August 5 in Nature Medicine, found that the DASH4D diet helped participants with type 2 diabetes control glucose levels.
For the study, 89 participants with type 2 diabetes ate prepared meals at a clinical research center for 20 weeks, half of the time on the DASH4D diet and half on a standard diet modeled after what U.S. adults typically eat. Participants' blood glucose levels were measured using wearable continuous glucose monitoring (CGM) devices.
The new study, named DASH4D CGM, found that when participants consumed the DASH4D diet, they had a clinically meaningful reduction of average blood glucose level and an increase in average time spent with blood glucose in the recommended range compared to when they consumed a standard diet. Participants eating the DASH4D diet had blood sugar levels that were on average 11 mg/dL lower than when eating the standard diet and stayed in the optimal blood glucose range for an extra 75 minutes a day.
Both effects are considered clinically meaningful for people with diabetes, as they may lower risks of heart disease, kidney disease, and other long-term adverse consequences of diabetes. The researchers hope that the results will lead to incorporating the DASH4D diet into clinical guidelines and improve type 2 diabetes management in the broader population.
"The original DASH diet has long been recommended for people with diabetes and other health conditions due to its effectiveness in lowering blood pressure, but this is the first time a controlled study has shown a significant improvement in glucose control as well," says study senior author Elizabeth Selvin , PhD, MPH, Director of the Welch Center for Prevention, Epidemiology and Clinical Research and professor in the Bloomberg School's Department of Epidemiology.
"Larger improvements were seen in participants who had higher blood glucose levels at the start of the trial," says Michael Fang , PhD, MHS, an assistant professor also in the Bloomberg School's Department of Epidemiology. "For those with the highest glucose levels—HbA1c above 8%—the DASH4D diet increased their time in the optimal blood glucose range by about three hours per day—a very significant benefit."
Diabetes and hypertension are widespread in the U.S. largely because of unhealthy diets high in animal fat, sugar, and salt. An estimated 35 million Americans have type 2 diabetes, according to the Centers for Disease Control and Prevention. Several large clinical trials have shown that the DASH diet—which limits meat, sugary and salty foods, and sugary drinks and is rich in fruits, vegetables, and whole grains—is effective in reducing high blood pressure.
The DASH4D CGM study led by Selvin was part of a larger Hopkins-led clinical trial , published this spring. The main trial found the DASH4D diet lowered blood pressure among individuals with type 2 diabetes.
Of the 89 people who completed the DASH4D CGM study, 67% were female and 88% were African American. Trained staff prepared meals—eventually totaling more than 40,000—for participants at a central testing site during the 2021–2024 study period. Each participant spent, in a random order, five weeks on a low-sodium DASH4D diet, five weeks on a high-sodium DASH4D diet, and five weeks each on low-sodium and high-sodium standard diets. (Sodium levels differed in order to test the effects of sodium on hypertension.) Participants wore CGM devices during weeks three and four in every five-week diet period. All the diets had the same number of calories.
"This trial design is what we call a 'crossover' design—we compared participants with themselves under different diet conditions, which reduced inter-individual variability and enhanced statistical power, allowing us to detect meaningful treatment effects despite what might initially appear to be small sample size," Selvin says.
For participants on the DASH4D diet, blood glucose levels also were less variable generally, and did not enter the hypoglycemic range any more often than for the standard diets.
"We're encouraged by these results and believe this can make a major impact on population health," says Fang. "The DASH4D diet was specifically designed to be sustainable and easy to follow."
" DASH4D Diet for Glycemic Control and Glucose Variability in Type 2 Diabetes: A Randomized Crossover Trial " was co-authored by Michael Fang, Dan Wang, Casey Rebholz, Justin Echouffo-Tcheugui, Olive Tang, Nae-Yuh Wang, Christine Mitchell, Scott Pilla, Lawrence Appel, and Elizabeth Selvin.
The study was funded by the National Institute of Diabetes and Digestive and Kidney Diseases (R01DK128900, K23DK128572, and K01DK138273) and the National Heart, Lung, and Blood Institute (T32HL007024 and K23HL153774). Abbott Diabetes Care provided the CGM systems for the study.
