It is already known that short chain fatty acids (SCFAs) - produced by bacteria in the gut during fermentation of insoluble fibre - have health promoting effects but that all fermentable fibres are not equally capable of stimulating SCFA production.
Therefore a new study, led by Dr Thomas Schmidt from the University of Michigan, explored the gut microbiota’s capacity for producing SCFAs through different fermentable fibres including: resistant starch from potatoes; resistant starch from maize; inulin from chicory root and rapidly digestible corn starch for the control.
Researchers said: "[The study] highlighted the importance of the composition of an individual’s microbiota in determining whether or not they respond to a specific dietary supplement."
Although all three fibres changed participants’ faecal microbiota, the results showed potato starch led to the greatest increase in SCFAs and revealed the existence of a high inter-individual variability in gut microbiome responses to diet.
Resistant starch from potatoes exhibited an increase in the levels of bifidobacteria. However, higher faecal butyrate concentrations were observed in individuals who responded to the dietary intervention with an increase in Ruminococcus bromii or Clostridium chartatabidum.
In addition, the abundance of the butyrate producer Eubacterium rectale both before and during dietary supplementation with resistant potato starch correlated positively with faecal butyrate concentrations.
These results show the existence of a high inter-individual variability in gut microbiome responses to diet, as individual microbiome at baseline determines the response to different fermentable fibres.
The researchers supplemented the habitual diets of 174 healthy young adults for two weeks with different types of fermentable fibres.
Changes in gut microbiota composition were assessed using 16S ribosomal ribonucleic acid gene sequencing and the function of the colon’s bacterial communities was explored by quantifying faecal SCFA concentrations before and during dietary supplementation.
Rise of prebiotics
Other than with the control compound, this study ensured to use fibres resistant to degradation by host enzymes meaning they would pass through the small intestine to the colon to ensure they could be metabolised by good bacteria therefore providing a prebiotic effect.
There is a growing interest in the importance of prebiotics to gut health as they are known to induce the growth or activity of beneficial bacteria in the gut.
Studies have shown that feeding beneficial gut bacteria with fibre helps a signalling mechanism which limits the growth of harmful pathogens.
A study in 2018 showed that consuming dietary fibres does lead to higher levels of Bifidobacterium spp. and Lactobacillus spp., as well as a higher level of the SCFA butyrate, compared with placebo/low-fibre.
“Dynamics of human gut microbiota and short-chain fatty acids in response to dietary interventions with three fermentable fibers.”
Authors: Baxter NT, Schmidt AW, Venkataraman A, et al.