Scientists develop targeted approach to fiber for gut health

Gut ecosystems are competitive environments with a few trillions of bacteria eager to take advantage of prebiotic fibers.

According to the study team, this is the first time that the specificity of fibers has been linked to “similarity and intensity of response in a distinct human gut microbiota”And they claim that the data offers “A new approach to design prebiotic or synergistic interventions based on symbionts…. with the possibility of being effective in a large number of subjects.

The in vitro investigation into the impact of fiber specificity on the structure of the microbiota indicates that high specificity fibers (and specifically insoluble β-glucan) can potentially bypass competition for the use of fiber in order to increase target bacteria and promote significant changes in gut microbes.

“Our results imply that fibers with high specificity generate more dramatic gut microbial changes than those with low specificity, which has potential implications not only for the microbial ecology itself, but also for aspects of clinical relevance.”

Intestinal microbiota

Dietary fibers (prebiotics) are carbohydrate polymers and oligomers made up of one or more types of sugar units (such as xylose, fructose, glucose, galactose, arabinose, rhamnose) and promote colonic health and systemic, but they elicit different and unpredictable responses to the gut microbiota.

The chemical and physical properties of fibers define how well gut bacteria will respond to supplementation and depend on the makeup of an individual’s basic gut ecosystem, which is affected by factors such as diet and genetics, scientists explain.

“The overall composition of the gut microbiota establishes the competitive environment of target bacteria for nutrient acquisition and utilization and has been shown to be an important driving force for inter-individual variability in fiber responses.”

The team hypothesized that structurally complex fibers (classified as high specificity fibers) could be selected to limit the number of target bacteria and reduce competitive pressures for the substrate. This would promote an increase in target bacteria (independent of the overall microbial community) and encourage similar microbial changes in subjects with markedly different microbiota environments.

High specificity fiber

To test their theory, fibers were classified into low specificity (fructooligosaccharides), low to intermediate (resistant starch type 2), intermediate (pectin) and high (insoluble β-1,3-glucan) and fermentation of the microbiota was assessed using fecal inoculum from 10 healthy subjects with different gut microbiota ratios.

The analyzes determined individual changes in the target bacteria which confirm that divergent fiber responses occur when using the two low specificity dietary fibers. Intermediate and high specificity fibers elicited similar responses in subjects in favor of target bacteria and high specificity dietary fibers. This promoted dramatic changes in the structure of the microbial community, compared to fibers with low specificity.

The results show that high specificity fibers induce similar fibers as long as the target bacteria are present. No discriminating characteristics were found for low and low to intermediate specificity fibers, confirming a lack of specificity of these fibers for specific bacteria in the participants.

The authors commented: “The high insoluble specificity ??-glucan promoted a strong increase in target bacteria (from 0.3 to 16.5% on average for Anaerostipes sp. and 2.5 to 17.9% on average for Bacteroides uniformis). “

These were associated with increases in the ratios of related metabolites (butyrate and propionate, respectively) in each microbial community in which these bacteria were present, which help support many essential body functions, they explained.


The study has potential limitations in the absence of testing for any other state of intermediate specificity not assessed here and the researchers suggest that a more precise method to determine the degree of specificity of fibers should be developed.

“This could include machine learning to link fiber structure and bacterial gene expression for hierarchical classification of fibers.

In vivoTests to confirm specificity results are also recommended because in vitroThe models lack factors, such as the presence of other energy sources for the bacteria, that could affect the results, they said.

Source: American Society for Microbiology

Posted in May / June 2021

“Hierarchical specificity of dietary fiber: the missing link for predictable and strong changes in intestinal bacterial communities”

Authors: Thaisa M. Cantu-Jungles, Nuseybe Bulut, Eponine Chambry, Andrea Ruthes, Marcello Iacomini, Ali Keshavarzian, Timothy A. Johnson, Bruce R. Hamaker

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