Title: Functional Dietary Fibre in the Gastrointestinal Tract: from Physical Interactions and Biochemical Transformations to Health Benefits

This talk considers the journey of dietary fibre along the gastrointestinal tract: from oral processing to colonic fermentation. Our primary focus is placed on uncovering how different physical interactions and biochemical transformations elicit specific physiological responses, leading to positive health outcomes and long-term wellbeing benefits. First, we consider a new definition of dietary fibre which provides physiology-based categorisation of fibre materials beyond the currently prevalent "soluble/insoluble" classification. This new outlook on the fibre properties and structure opens a new perspective on the mechanisms by which dietary fibre function in the gut. From the effect of fibre polysaccharides on gastric emptying, starch hydrolysis and lipid transformations in the small intestine, to the complex fermentation pathways of plant cell wall particles in the colon – we discover that such fundamental physical properties as hydration and structuring underpin physiological functionality of dietary fibre. The emerging evidence suggests that optimisation of fibre structure and functionality can lead to the improved glycaemic response, reduced risk of cardiovascular diseases and colon cancers, as well as it has a marked impact on systemic metabolism, from controlling the hepatic function to influencing the gut-brain axis. Ultimately, we overview principal avenues for a targeted design of dietary fibre materials to generate healthy foods with specific sets of physiological responses and desired health and wellbeing benefits.

Keywords: Fibre, gastrointestinal tract, interaction, transformation