• David J A Jenkins, Cyril W C Kendall, Gail McKeown-Eyssen, Robert G Josse, Jay Silverberg, Gillian L Booth, Edward Vidgen, Andrea R Josse, Tri H Nguyen, Sorcha Corrigan, Monica S Banach, Sophie Ares, Sandy Mitchell, Azadeh Emam, Livia S A Augustin, Tina L Parker, and Lawrence A Leiter.
• Clinical Nutrition and Risk Factor Modification Center, St Michael's Hospital, Toronto, Ontario, Canada.
• JAMA. 2008 Dec 17; 300 (23): 274227532742-53.

ContextClinical trials using antihyperglycemic medications to improve glycemic control have not demonstrated the anticipated cardiovascular benefits. Low-glycemic index diets may improve both glycemic control and cardiovascular risk factors for patients with type 2 diabetes but debate over their effectiveness continues due to trial limitations.ObjectiveTo test the effects of low-glycemic index diets on glycemic control and cardiovascular risk factors in patients with type 2 diabetes.Design, Setting, And ParticipantsA randomized, parallel study design at a Canadian university hospital research center of 210 participants with type 2 diabetes treated with antihyperglycemic medications who were recruited by newspaper advertisement and randomly assigned to receive 1 of 2 diet treatments each for 6 months between September 16, 2004, and May 22, 2007.InterventionHigh-cereal fiber or low-glycemic index dietary advice.Main Outcome MeasuresAbsolute change in glycated hemoglobin A(1c) (HbA(1c)), with fasting blood glucose and cardiovascular disease risk factors as secondary measures.ResultsIn the intention-to-treat analysis, HbA(1c) decreased by -0.18% absolute HbA(1c) units (95% confidence interval [CI], -0.29% to -0.07%) in the high-cereal fiber diet compared with -0.50% absolute HbA(1c) units (95% CI, -0.61% to -0.39%) in the low-glycemic index diet (P < .001). There was also an increase of high-density lipoprotein cholesterol in the low-glycemic index diet by 1.7 mg/dL (95% CI, 0.8-2.6 mg/dL) compared with a decrease of high-density lipoprotein cholesterol by -0.2 mg/dL (95% CI, -0.9 to 0.5 mg/dL) in the high-cereal fiber diet (P = .005). The reduction in dietary glycemic index related positively to the reduction in HbA(1c) concentration (r = 0.35, P < .001) and negatively to the increase in high-density lipoprotein cholesterol (r = -0.19, P = .009).ConclusionIn patients with type 2 diabetes, 6-month treatment with a low-glycemic index diet resulted in moderately lower HbA(1c) levels compared with a high-cereal fiber diet. Trial Registration clinicaltrials.gov identifier: NCT00438698.

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