Altering source or amount of dietary carbohydrate has acute and chronic effects on postprandial glucose and triglycerides in type 2 diabetes: Canadian trial of Carbohydrates in Diabetes (CCD)

Abstract

Background and aims: Nutrition recommendations for type 2 diabetes (T2DM) are partly guided by the postprandial responses elicited by diets varying in carbohydrate (CHO). We aimed to explore whether long-term changes in postprandial responses on low-glycemic-index (GI) or low-CHO diets were due to acute or chronic effects in T2DM.

Methods and results: Subjects with diet-alone-treated T2DM were randomly assigned to high-CHO/high-GI (H), high-CHO/low-GI (L), or low-CHO/high-monounsaturated-fat (M) diets for 12-months. At week-0 (Baseline) postprandial responses after H-meals (55% CHO, GI = 61) were measured from 0800 h to 1600 h. After 12 mo subjects were randomly assigned to H-meals or study diet meals (L, 57% CHO, GI = 50; M, 44% CHO, GI = 61). This yielded 5 groups: H diet with H-meals (HH, n = 34); L diet with H- (LH, n = 17) or L-meals (LL, n = 16); and M diet with H- (MH, n = 18) or M meals (MM, n = 19). Postprandial glucose fluctuations were lower in LL than all other groups (p < 0.001). Changes in postprandial-triglycerides differed among groups (p < 0.001). After 12 mo in HH and MM both fasting- and postprandial-triglycerides were similar to Baseline while in MH postprandial-triglycerides were significantly higher than at Baseline (p = 0.028). In LH, triglycerides were consistently (0.18-0.34 mmol/L) higher than Baseline throughout the day, while in LL the difference from Baseline varied across the day from 0.04 to 0.36 mmol/L (p < 0.001).

Conclusion: Low-GI and low-CHO diets have both acute and chronic effects on postprandial glucose and triglycerides in T2DM subjects. Thus, the composition of the acute test-meal and the habitual diet should be considered when interpreting the nutritional implications of different postprandial responses.