Investigations of mechanisms involved in postprandial glycemia attenuation with dietary fiber consumption
Earlier studies have shown that dietary fibre (DF) can attenuate glycemic response through its ability to alter luminal viscosity and could therefore help minimize the risk of developing Type 2 diabetes (T2D). The main objective of the present work was to gain more understanding of mechanisms involved in attenuation of postprandial glycemic and insulinemic responses as a result of DF intake. Four different DF types, including yellow mustard mucilage, soluble flaxseed gum, fenugreek gum and oat gum, were used in the present study. Concentrations of each DF type that resulted in apparent viscosities (at 60 s-1) close to apparent viscosities of oat β-glucan were determined. Besides that, the effect of DF on amylolysis and maltose transport in simulated small intestinal conditions at controlled shear rate was studied. Furthermore, a human clinical trial was conducted to investigate the effect of DF on postprandial glycemic and insulinemic responses. Participants consumed high maltose syrup-based and starch-based treatments supplemented with each type of DF at concentrations matching their viscosity (18.54 mPa.s at 60 s-1) as measured in simulated small intestinal conditions. Concentrations of DFs that resulted in similar apparent viscosities in the simulated small intestinal conditions were different for each DF type. Nonetheless, the presence of DF at different concentrations, but matched for simulated intestinal viscosity, resulted in similar progress of amylolysis in vitro. Maltose transport, measured in vitro, was not affected by the DF at concentrations expected to be in the small intestinal lumen after consumption of the corresponding pudding treatments. Supplementation of puddings with each type of DF at different concentrations but matched for post-digestion viscosity attenuated postprandial blood glucose and plasma insulin peak concentrations and plasma paracetamol concentration to a similar extent, which was significantly lower compared to the control. It was concluded that improvement of blood biochemical profile observed in the present study was due to the ability of DF to alter digesta viscosity through mechanisms including the delay of gastric emptying and to some degree reduction of amylolysis progress.