Abstract
Research characterising the gut microbiota in different populations and diseases has mushroomed since the advent of next-generation sequencing techniques. However, there has been less emphasis on the impact of dietary fibres and other dietary components that influence gut microbial metabolic activities. Dietary fibres are the main energy source for gut bacteria. However, fibres differ in their physicochemical properties, their effects on the gut and their fermentation characteristics. The diversity of carbohydrates and associated molecules in fibre-rich foods can have a major influence on microbiota composition and production of bioactive molecules, for example SCFAs and phenolic acids. Several of these microbial metabolites may influence the functions of body systems including the gut, liver, adipose tissues and brain. Dietary fibre intake recommendations have recently been increased (to 30 g daily) in response to growing obesity and other health concerns. Increasing intakes of specific fibre and plant food sources may differentially influence the bacteria and their metabolism. However, in vitro studies show great individual variability in the response of the gut microbiota to different fibres and fibre combinations, making it difficult to predict which foods or food components will have the greatest impact on levels of bioactive molecules produced in the colon of individuals. Greater understanding of individual responses to manipulation of the diet, in relation to microbiome composition and production of metabolites with proven beneficial impact on body systems, would allow the personalised approach needed to best promote good health.
Highlights
The relationship between dietary fibre and the gut microbiota is complex, and there is still much that we do not understand
Several dietary components could influence individual bacteria species directly or via alterations in gut transit and digestive functions but the main influence is likely to be through dietary fibre
Dietary fibre was originally defined as carbohydrate polymers within plant cell wall structures that escape digestion and absorption in the small intestine[10]
Summary
Research characterising the gut microbiota in different populations and diseases has mushroomed since the advent of next-generation sequencing techniques. The diversity of carbohydrates and associated molecules in fibre-rich foods can have a major influence on microbiota composition and production of bioactive molecules, for example SCFAs and phenolic acids. Several of these microbial metabolites may influence the functions of body systems including the gut, liver, adipose tissues and brain. The physiological impact of this relationship can vary depending on many different factors including the type of fibre consumed, background diet, gut microbiota composition as well as variations in how these affect digestive function and sensitivity along the gastrointestinal tract of individuals. Dietary fibre and the gut microbiota have their own well established physiological effects, it is the interaction between these two that has drawn growing interest[7–9]
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