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.
BACKGROUND
The optimal source and amount of dietary carbohydrate for managing type 2 diabetes (T2DM) are unknown.


OBJECTIVE
We aimed to compare the effects of altering the glycemic index or the amount of carbohydrate on glycated hemoglobin (HbA1c), plasma glucose, lipids, and C-reactive protein (CRP) in T2DM patients.


METHODS
Subjects with T2DM managed by diet alone (n=162) were randomly assigned to receive high-carbohydrate, high-glycemic-index (high-GI), high-carbohydrate, low-glycemic-index (low-GI), or low-carbohydrate, high-monounsaturated-fat (low-CHO) diets for 1 y.


RESULTS
The high-GI, low-GI, and low-CHO diets contained, respectively, 47%, 52%, and 39% of energy as carbohydrate and 31%, 27%, and 40% of energy as fat; they had GIs of 63, 55, and 59, respectively. Body weight and HbA1c did not differ significantly between diets. Fasting glucose was higher (P=0.041), but 2-h postload glucose was lower (P=0.010) after 12 mo of the low-GI diet. With the low-GI diet, overall mean triacylglycerol was 12% higher and HDL cholesterol 4% lower than with the low-CHO diet (P<0.05), but the difference in the ratio of total to HDL cholesterol disappeared by 6 mo (time x diet interaction, P=0.044). Overall mean CRP with the low-GI diet, 1.95 mg/L, was 30% less than that with the high-GI diet, 2.75 mg/L (P=0.0078); the concentration with the low-CHO diet, 2.35 mg/L, was intermediate.


CONCLUSIONS
In subjects with T2DM managed by diet alone with optimal glycemic control, long-term HbA1c was not affected by altering the GI or the amount of dietary carbohydrate. Differences in total:HDL cholesterol among diets had disappeared by 6 mo. However, because of sustained reductions in postprandial glucose and CRP, a low-GI diet may be preferred for the dietary management of T2DM.
Wolever
Thomas M S
TM
Department of Nutritional Sciences, University of Toronto, and the Department of Medicine, St Michael's Hospital, Toronto, Ontario, Canada. thomas.wolever@utoronto.ca
Gibbs
Alison L
AL
Mehling
Christine
C
Chiasson
Jean-Louis
JL
Connelly
Philip W
PW
Josse
Robert G
RG
Leiter
Lawrence A
LA
Maheux
Pierre
P
Rabasa-Lhoret
Remi
R
Rodger
N Wilson
NW
Ryan
Edmond A
EA
D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism; D002097:C-Reactive Protein / Q000378:metabolism*; D002784:Cholesterol / Q000097:blood; D008076:Cholesterol, HDL / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000178:diet therapy*; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000145:classification / Q000378:metabolism; D004041:Dietary Fats / Q000008:administration & dosage*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D038321:Glycemic Index; D006801:Humans; D008055:Lipids / Q000097:blood; D008297:Male; D008875:Middle Aged
D001786:Blood Glucose; D002097:C-Reactive Protein; D002784:Cholesterol; D008076:Cholesterol, HDL; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D006442:Glycated Hemoglobin; D008055:Lipids