Dietary fibre for glycaemia control: Towards a mechanistic understanding

Abstract

One of the many functional benefits of dietary fibre when present in the human diet is its ability to reduce the rate of absorption of glucose after consumption of high glycaemic carbohydrate-containing foods, leading to a blunted blood glucose response curve and less demand for insulin. Glycaemia control through dietary intervention is of significant importance to those at high risk for Type 2 Diabetes Mellitus (T2D), or those with Impaired Glucose Tolerance or with T2D, populations that are growing globally at an alarming rate. The soluble polysaccharide gums are well known to induce viscosity and/or gelation in solution, and their physiological function is often related to this rheological behaviour. However, gastrointestinal secretions and dilution, and acidification and re-neutralization, can affect the rheological properties of the polysaccharides in vivo. When one considers the physiology of starch and sugar digestion and glucose absorption, it is possible to elucidate several plausible mechanisms by which both soluble and insoluble fibres might contribute to Glycaemia control: reduction in gastric emptying, modification of release of digestion- and fermentation-related hormones, inhibition of amylase activity and delayed starch hydrolysis, reduction in diffusion of amylolytic products to the small intestinal microvilli, and/or the development of an absorptive barrier layer through interactions with the mucosa. Scientific evidence suggests that all of these mechanisms are involved to some extent. Understanding the relationships between molecular structure, physical functionality and physiological functionality of dietary fibres should enable the food industry to deliver more fibre-enriched functional food products to consumers, especially for Glycaemia control.