Effect of carbohydrate distribution on postprandial glucose peaks with the use of continuous glucose monitoring in type 2 diabetes

Background: Large postprandial glucose peaks are associated with increased risk of diabetic complications and cardiovascular disease. Objective: We investigated the effect of carbohydrate distribution on postprandial glucose peaks with continuous blood glucose monitoring (CGMS), when consuming a moderate carbohydrate diet in energy balance in subjects with type 2 diabetes. Design: Twenty-three subjects with type 2 diabetes were randomly assigned to each of four 3-d interventions in a crossover design with a 4-d washout period. Identical foods were provided for each treatment with a ratio of total carbohydrate to protein to fat of 40%:34%:26% but differing in carbohydrate content at each meal: even distribution (CARB-E; ≈70g carbohydrate), breakfast (CARB-B), lunch (CARB-L), and dinner(CARB-D), each providing ≈125 g carbohydrate in the loaded meal in a 9-MJ diet. Glucose concentrations were continuously measured with CGMS. Outcomes were assessed by postprandial peak glucose (G_max), time spent > 12 mmol/L (T > 12), and total area under the glucose curve (AUC₂₀). Results: Daily G_max differed between treatments (P = 0.003) with CARB-L (14.2 ± 1.0 mmol/L), CARB-E (14.5 ± 0.9 mmol/L), and CARB-D (14.6 ± 0.8 mmol/L) being similar but lower than CARB-B (16.5 ± 0.8 mmol/L). Meal G_max was weakly related to carbohydrate amount and glycemic load (r = 0.40-0.44). T > 12 differed between treatments (P = 0.014), and a treatment x fasting blood glucose (FBG) interaction (P = 0.003) was observed with CARB-L (184 ± 74 min) < CARB-B (190 ± 49 min) < CARB-D (234 ± 87 min) < CARB-E (262 ± 91 min). Total AUC₂₀ was not significantly different between treatments. After adjustment for FBG, treatment became significant (P = 0.006); CARB-L(10 049 ± 718 mmol/L x 20 h) < CARB-E (10 493 ± 706 mmol/L x 20 h) < CARB-B(10 603 ± 642 mmol/L x 20 h) < CARB-D(10 717 ± 638 mmol/L x 20 h). Conclusion: CARB-E did not optimize blood glucose control as assessed by postprandial peaks, whereas CARB-L provided the most favorable postprandial profile.