Dietary Fibers Promote Healthy Gut Bacteria Activity: Study

Consuming fruits, vegetables, and whole grains provides us with healthy dietary fibres.

Researchers from the University of Copenhagen have now found that these fibres are essential in maintaining a balance between the production of beneficial and harmful substances in the colon by influencing bacterial behavior.

The research, published in the scientific journal Nature Microbiology, revealed that different types of bacteria in our colon compete to utilize the essential amino acid tryptophan, leading to either beneficial or harmful outcomes for our health. The study found that consuming a high amount of dietary fiber helps gut bacteria convert tryptophan into beneficial substances.

Researchers have discovered that dietary fibres, found in fruits, vegetables, and whole grains, not only convert into healthy short-chain fatty acids but also prevent tryptophan from becoming harmful substances, instead promoting its conversion into beneficial compounds. This highlights how dietary fibres influence gut bacteria composition and behavior, contributing to overall health. Protein-rich foods like chicken, turkey, salmon, eggs, and legumes are key sources of tryptophan, which must be obtained through diet.

Through multiple experiments in bacterial cultures and mice, the researchers demonstrated that fibre-degrading gut bacteria, such as B. thetaiotaomicron, regulate the indole-forming activity of E. coli.

The gut bacterium E. coli can turn tryptophan into a harmful compound called indole, which is associated with the progression of chronic kidney disease. But another gut bacterium, C. sporogenes, turns tryptophan into healthy substances associated with protection against inflammatory bowel diseases, type 2 diabetes, cardiovascular diseases, and neurological diseases.

B. thetaiotaomicron assists by breaking down fibres into simple sugars, which E. coli prefers over tryptophan for growth. The sugar components from the fibres prevent E. coli from turning tryptophan into indole, thereby allowing C. sporogenes to utilize tryptophan to produce healthy compounds.

"These results emphasize that our dietary habits significantly influence the behavior of gut bacteria, creating a delicate balance between health-promoting and disease-associated activities. In the long term, the results can help us design dietary programs that prevent a range of diseases," said Tine Rask Licht, professor at DTU National Food Institute.

Reference: Sinha, A.K., Laursen, M.F., Brinck, J.E. et al. Dietary fibre directs microbial tryptophan metabolism via metabolic interactions in the gut microbiota. Nat Microbiol (2024). https://doi.org/10.1038/s41564-024-01737-3