Applied nutritional investigationA randomized clinical trial comparing low–glycemic index versus ADA dietary education among individuals with type 2 diabetes
Introduction
Diabetes can be associated with serious complications. Microvascular complications such as retinopathy, nephropathy, and neuropathy are believed to result from chronically elevated blood glucose levels [1], [2], [3], [4]. In addition, recent evidence suggests a clear effect of glycemic control on macrovascular complications such as coronary heart disease and stroke, which are the primary causes of death in persons with diabetes [5]. These devastating complications are, to a large extent, preventable through the improvement of glycemic control [6], [7].
Dietary management is the cornerstone of care for diabetes, and carbohydrate intake has the greatest influence on blood glucose. Based on American Diabetes Association (ADA) recommendations [8], [9], [10], carbohydrates should provide 45% to 65% of total energy intake. The ADA diet, which emphasizes carbohydrate counting (grams of carbohydrate) and even distribution (timing) of daily carbohydrate intake, is currently recommended for patients with diabetes as the mainstay of glycemic control.
Carbohydrate foods and their glycemic responses have been classified by the glycemic index (GI). The GI of a food is defined as the glucose response during a 2-h period after consumption of 50 g of carbohydrate from the specific test food, divided by the glucose response after consumption of 50 g of carbohydrate from a control food, which generally is white bread or glucose [11]. Glycemic load (GL) is a calculation of the GI value of a food multiplied by its total available carbohydrate content.
A recent meta-analysis of randomized clinical trials [12] suggests that a low-GI diet has a moderate effect on improving short-term glycemic control in diabetic patients [12]. However, in most of the reviewed randomized clinical trials, patients were fed experimental diets. Therefore, the feasibility of the low-GI diet in the clinical setting remains unknown. In addition, there is no evidence that long-term consumption of a low-GI diet will contribute to improved glycemic control in people with diabetes [9], [13]. Diabetic care usually requires medication and optimal dietary management, with the latter decreasing the dependence on diabetic medications for control of glycosylated hemoglobin (HbA1c). Diabetic medication changes should be assessed when a co-therapy, such as dietary counseling, is administered.
The objective of the present study was to examine the efficacy of low-GI dietary education compared with the ADA dietary education on glycemic control, diabetic medication change, blood lipids, blood pressure, body weight, and dietary GI score for patients with type 2 diabetes.
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Study subjects
The study population was recruited for the Diabetic Educational Eating Plan study (ClinicalTrials.gov identifier: NCT00473811) from a primary care setting at the university campus of the University of Massachusetts Memorial Healthcare Center (UMMHC). Detailed study methodology was described elsewhere [14]. Briefly, subjects were randomized to a low-GI diet or the standard ADA diet. Study eligibility included a diagnosis of type 2 diabetes documented in the patient’s medical chart; an HbA1c
Results
Participants were 33 to 77 y old (mean ± SD 53.5 ± 8.4). Ninety-five percent were overweight or obese with a mean BMI of 35.8 kg/m2 (Table 3). Fifty-three percent were female, and 53% had a bachelor’s degree or higher education. Fifty-five percent were employed full time. Participants were predominantly white (85%) and married or living with a partner (70%). Ninety percent (n = 36) were taking medication for diabetes. Detailed diabetes medication use information at baseline was reported
Discussion
Compared with the ADA diet, the low-GI diet led to a reduction in the use of diabetic medication while achieving equivalent control of HbA1c and blood lipids. Despite its limited size, this trial suggests that the low-GI diet may be an alternative to the conventional ADA diet. This finding should be evaluated in a larger randomized controlled trial.
The ADA and low-GI diets resulted in significant and comparable improvements in HbA1c and lipid profiles. The ADA diet has changed over the years
Conclusions
Compared with the ADA diet, the low-GI diet achieved equivalent control of HbA1c using less diabetic medication. We conclude that the low-GI diet is a viable alternative to the standard ADA diet. Findings should be evaluated in a larger randomized controlled trial.
Acknowledgments
The authors thank Dr. Judith K. Ockene for her consistent encouragement and support of this work; Andrea Hafner for coordinating the early part of the study; Victoria Andersen and Betsy Costello for conducting the dietary intervention; Paul S. Haberman for critical review of the manuscript; and Annabella Aguirre for maintaining and ensuring integrity of blood samples from collection through analysis.
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The project described was supported by grant 5 P30 DK032520 from the National Institute of Diabetes and Digestive and Kidney Diseases.