Dietary Fibre: More than a Prebiotic

Dietary fibre has been shown to have a range of functionality in the upper GI tract. The presence of fibre can alter gastric emptying thus affecting fullness and satiety. These alterations are a result of differences in nutrient release and nutrient sensing in the duodenum. The current proposed mechanisms for the cholesterol lowering effects involve disruption of the normal recycling of bile possibly by sequestering bile salts and fatty acids or by significantly decreasing the rate of absorption as a result of entanglement with intestinal mucus. In experiments simulating the digestion of bread we studied the effect of the addition of beta glucan. Clearly in the early stage of digestion the starch provides most of the rheological properties of the system. The results show that although dietary fibre may significantly increase viscosity of digesta from the later stages of the simulation, it has minimal impact of the rates of hydrolysis of both protein and starch. However, using quantitative confocal microscopy methods such as FRAP and multiple particle tracking has provided evidence that dietary fibre can combine with intestinal mucus and produce a layer that significantly delays the transport of lipid digestion products. These results highlight the complexity of possible roles for dietary fibre in the upper GI tract.