Investigating the impact of dietary fibre on the gut microbiota

Diets low in complex polysaccharides have been shown to perturb the gut microbiota-host relationship, and thus impact host health. As evidence supporting this hypothesis continues to grow, therapeutic modulation of the gut microbiota through supplementation of complex polysaccharides for preventing or treating diseases has gained significant scientific and commercial interest. Several supplements in the form of dietary fibre or prebiotics are marketed commercially for this purpose. However, only limited work has been conducted to scientifically evaluate the ability of these products to alter the gut microbiota and improve host health. In this work, we investigated the impact of commercially available dietary fibre and cereal products on the gut microbiota and metabolite production. We used an in vitro adult digestive and gut microbiota model system and a high fat diet fed mouse model to examine the effect of dietary fibre supplementation on the gut microbiota, metabolites and host physiology. Using an in vitro infant digestive and gut microbiota model system we investigated the impact of cereal products on the infant gut microbiota and metabolites. Our results demonstrated significant shifts in the overall gut microbiota community structure upon addition of each product. The abundance of various bacterial taxa associated with fibre digestion and anti-inflammatory capabilities increased with fibre additions. However, the specific nature of the alterations was product-dependent. Fibre supplementation in mice ameliorated high fat diet-induced changes in the abundance of specific gut bacteria, whilst no significant changes in the glucose clearance or body weight were observed. Further, we demonstrated significant differences in the gut microbiota response to a high fat diet and fibre supplementation upon weekly overnight fasting in mice. The product-dependent impact on the gut microbiota and metabolites highlights the need for stringent scientific evaluation of commercial fibre products for their effect on the gut microbiota and host physiology.