Dietary fibers are major modulators of gut microbiota composition and function, and their immunological effects are increasingly recognized as an important component of host health. However, dietary fibers are structurally diverse, and their impacts on intestinal immunity cannot be explained simply by total fiber intake. Our studies have focused on how individual dietary fibers regulate intestinal immune homeostasis, particularly through the induction of regulatory T cells (Tregs) and the modulation of inflammatory responses.

Short-chain fatty acids, especially butyrate, produced through microbial fermentation of dietary fibers, promote the differentiation of colonic Tregs, at least in part through inhibition of histone deacetylases. This pathway provides a mechanistic link between microbial metabolism and epigenetic regulation of intestinal immune tolerance. Based on this concept, we have been screening dietary fibers for their ability to induce colonic Treg. Our findings suggest that the immunological activity of dietary fibers differs substantially depending on their physicochemical properties and fermentability, and that only certain fibers efficiently promote Treg accumulation.

In this presentation, I will summarize our experimental evidence linking dietary fibers to intestinal immune regulation, including the identification of Treg-inducing fibers that prevent experimental colitis.