The Canadian Trial of Carbohydrates in Diabetes (CCD), a 1-y controlled trial of low-glycemic-index dietary carbohydrate in type 2 diabetes: no effect on glycated hemoglobin but reduction in C-reactive protein.

Description

Wolever et al. report the results of the Canadian Trial on Carbohydrates in Diabetes (CCD), a long-term, multicentre, randomized controlled trial comparing the effects of altering the source or amount of dietary carbohydrates on several markers of the disease in 162 patients with type 2 diabetes managed by diet alone. The authors compared the effects of high-carbohydrate, high-glycemic-index (high-GI), high-carbohydrate, low-glycemic-index (low-GI) and low-carbohydrate, high-monounsaturated-fat (low-CHO) diets over 1 year on glycated hemoglobin (HbA1c), blood glucose, lipids, and C-reactive protein (CRP). Study results indicated that altering the glycemic index or the amount of dietary carbohydrates had no effect on HbA1c in patients with type 2 diabetes managed by diet alone. The 1 year intervention also revealed that a low-GI diet achieved sustained reductions in CRP levels along with reductions in postprandial glucose, suggesting that a low-GI diet may be preferable for the dietary management of type 2 diabetes. This paper was accompanied by two editorials by John M Miles and Xavier Pi-Sunyer who both recognized the uniqueness of Wolever et al.’s carefully conducted study. However, they drew attention to some intriguing findings that require further investigation, such as the mechanism by which a low-GI diet decreases CRP. Pi-Sunyer insisted that it could be misleading to attribute this finding to a change in postprandial glucose. Furthermore, Miles and Pi-Sunyer both questioned the role of GI in diabetes management. In accordance with a previous American Diabetes Association statement, Miles emphasized the need for prudence before concluding that low-GI diets reduce diabetes risk. Pi-Sunyer agreed, stressing the fact that it would be imprudent at this point to burden type 2 diabetic patients with the additional task of choosing among high-GI and low-GI foods. Further studies are clearly needed on this issue.