Impact of cereal fibre on glucose-regulating factors

Aims/hypothesis: Insoluble dietary fibre intake is associated, by unknown mechanisms, with a reduced risk of type 2 diabetes. We investigated whether a short-term dietary intervention with purified insoluble fibres influences acute and delayed responses of glucose, insulin, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1.Methods: Fourteen healthy women with NGT were studied for 300 min on six to eight occasions. Subjects consumed three matched portions of control (C) or fibre-enriched bread (10.4-10.6 g/portion; wheat fibre [WF], oat fibre [OF], and, in a substudy [n=9], resistant starch [RS]) followed by control (C-C, C-WF, C-OF, C-RS) on subsequent days. Results: Fibre enrichment accelerated the early insulin response (fibrextime interaction p=0.026 for WF, p < 0.001 for OF, p=0.126 for RS; time of maximal concentration [T-max], C 57.9 +/- 5.9, WF 49.3 +/- 2.5 [p=0.086], OF 46.1 +/- 2.9 [p=0.026], RS 46.7 +/- 5.8 min [p=0.029]). It was also associated with an earlier postprandial GIP response after OF (T-max, C 83.6 +/- 7.2, WF 70.7 +/- 6.0 [p=0.054], OF 64.3 +/- 6.9 [p=0.022], RS 60.0 +/- 5.0 [p > 0.15]). Increased fibre intake for 24 h was further associated with a reduced postprandial glucose response on the following day subsequent to ingestion of a control meal (AUC(C-C) 4,140 +/- 401, AUC(C-WF) 2,850 +/- 331 [p=0.007], AUC(C-OF) 2,830 +/- 277 [p=0.011]), with no difference in maximal concentration and T-max of glucose responses. No differences in insulin responses were observed 24 h after the fibre-enriched diets compared with control (p > 0.15). Colonic fermentation was increased only on study days C-OF (p=0.017) and C-RS (p=0.016). Conclusions/interpretation: The consumption of highly purified insoluble dietary fibres accelerated the acute GIP and insulin response and was further associated with enhanced postprandial carbohydrate handling the following day upon ingestion of a control meal.