Dietary fibre (DF), like other compounds present in the diet, can interact with any of the defensive mechanisms located in the intestine - gut bacteria (first line of defence), epithelial cells (second line of defence) or immune cells (third line of defence) from these mucosal sites - thereby acting as immunomodulatory agents. As DF is a complex and heterogeneous group of carbohydrates with different characteristics, its mechanisms and effects on the microbial and host cells are also dependent on their type. There are only a few in vitro, in vivo and clinical interventions on different DFs assessing their protective potential as anti-infective agents in the gastrointestinal tract. The immediate defensive properties —microbiota-independent— of DF involve direct effects on the intestinal environment (i.e. they modify other bioactive components’ bioavailability), interactions with pathogens and the host (i.e. modulating signalling pathways). In addition, some types of DF, which may be fermentable, can have microbiota-dependent effects on health. These mechanisms include their ability to change microbiota composition and consequently their functionality, which in turn promotes the production of short-chain fatty acids (SCFAs). These SCFAs have been described to potentially change the gut environment and influence both epithelial and immune cells located in the intestine through several mechanisms (i.e. gene expression modulation and direct receptor binding). Overall, these products lead to intestinal gut homeostasis.
Presented at the International Fibre Summit 2019 (https://internationalfibre.com/). Reproduced with permission from the organizers.