Fiber consumption protects gut from serious bacterial infection, study suggests

A study published in the journal Cell Host & Microbe by Brazilian and American researchers suggests that a diet rich in soluble fiber can protect the intestine against pathogenic bacteria.

The conclusion is based on experiments with mice exposed to Clostridioides difficile, which causes colon inflammation and diarrhea and affects about 500,000 people a year in the United States.

“We were able to treat the mice that had an infection with a diet supplemented with soluble fiber. This is digested by the intestinal microbiota, which produces compounds such as acetate. This initiates a cascade of interactions that leads to an appropriate immune response to deal with the infection,” explains José Fachi, first author of the study, conducted during his postdoctoral studies at Washington University School of Medicine in Saint Louis, United States.

The work was a collaboration between the institution and the State University of Campinas (UNICAMP) in Brazil. The authors observed that the mice that consumed a diet rich in soluble fiber produced more acetate in the intestine. This increase helped regulate the immune response in the layer that covers the inner wall of the organ, known as the epithelium, making it effective in fighting the C. difficile bacteria.

Acetate is a short-chain fatty acid produced by the digestion of soluble fibers, a process carried out by the bacteria that live in the intestine.

In the study, mice fed a low-fiber diet produced little acetate. As a result, the expression of components of the so-called major histocompatibility complex class 2 (MHC-II) was increased in the intestinal epithelium. Although MHC-II is an essential molecule in the defense against infection, its excessive production can cause exaggerated inflammation, which damages the tissues and worsens the patient’s condition.

“It’s a similar effect to what happens in severe COVID-19 when the immune response itself leads to tissue destruction and even death. In our study, the consumption of soluble fiber regulated this response,” says Sarah de Oliveira, a doctoral student at UNICAMP’s Institute of Biology (IB) and co-author of the article.

Reference:

Fachi JL, de Oliveira S, Trsan T, Penati S, Gilfillan S, Cao S, Ribeiro Castro P, Fernandes MF, Hyrc KL, Liu X, Rodrigues PF, Bhattarai B, Layden BT, Vinolo MAR, Colonna M. Fiber- and acetate-mediated modulation of MHC-II expression on intestinal epithelium protects from Clostridioides difficile infection. Cell Host Microbe. 2025 Feb 12;33(2):235-251.e7. doi: 10.1016/j.chom.2024.12.017.