Persons with type 2 diabetes who had a diet high in low-glycemic foods such as nuts, beans and lentils had greater improvement in glycemic control and risk factors for coronary heart disease than persons on a diet with an emphasis on high-cereal fiber, according to a randomized, parallel study design at a Canadian university hospital research center of 210 participants with type 2 diabetes.

The participants were randomly assigned to receive 1 of the 2 diet treatments for 6 months.

In the low–glycemic index diet, the following foods were emphasized: beans, peas, lentils, nuts, pasta, rice boiled briefly and low–glycemic index breads (including pumpernickel, rye pita, and quinoa and flaxseed) and breakfast cereals (including large flake oatmeal and oat bran). In the high–cereal fiber diet, participants were advised to take the "brown" option (whole grain breads; whole grain breakfast cereals; brown rice; potatoes with skins; and whole wheat bread, crackers, and breakfast cereals).

Three servings of fruit and five servings of vegetables were encouraged on both treatments.
The researchers found that hemoglobin A1c (HbA1c; a substance of red blood cells tested to measure the blood glucose level) decreased by .50 percent absolute HbA1c units in the low–glycemic index diet compared with .18 percent absolute HbA1c units in the high–cereal fiber diet. Significant treatment effects were observed for HDL cholesterol and the LDL cholesterol: HDL cholesterol ratio. HDL cholesterol increased in the low–glycemic index diet group by 1.7 mg/dL and decreased by .2 mg/dL in the high–cereal fiber diet group. The LDL cholesterol: HDL cholesterol ratio showed a greater reduction in the low–glycemic index diet group compared with the high–cereal fiber diet group.

"Lowering the glycemic index of the diet improved glycemic control and risk factors for coronary heart disease. These data have important implications for the treatment of diabetes where the goal has been tight glycemic control to avoid complications. The reduction in HbA1c was modest, but we think it has clinical relevance," the authors write. "Low–glycemic index diets may be useful as part of the strategy to improve glycemic control in patients with type 2 diabetes taking antihyperglycemic medications."

"Pharmacological interventions to improve glycemic control in type 2 diabetes have often failed to show a significant reduction in cardiovascular events. In view of the 2- to 4-fold increase in coronary heart disease risk in participants with type 2 diabetes, the ability of a low–glycemic index diet to address both glycemic control and coronary heart disease risk factors increases the clinical relevance of this approach for patients with type 2 diabetes, such as those in this study, who are overweight and also taking statins for coronary heart disease risk reduction."
Source:
David J. A. Jenkins, et al. Effect of a Low–Glycemic Index or a High–Cereal Fiber Diet on Type 2 Diabetes. JAMA. 2008;300(23):2742-2753.