Differential Effects of High-Fiber and Low-Fiber Diets on Antitumor Immunity and Colon Tumor Progression in a Murine Model.

The role of dietary fiber in colon cancer prevention remains controversial. We investigated its impact on antitumor immunity and the gut microbiota in APCmin/+ mice infected with enterotoxigenic Bacteroides fragilis. Mice were fed high-fiber, low-fiber, or chow diets, and the tumor burden, survival, cytokines, microbiota, and metabolites were analyzed. Contrary to the belief that high fiber inhibits tumor progression, it had no significant impact compared with chow diet. However, the low-fiber diet significantly reduced the tumor burden and improved survival. Mechanistically, high fiber increased proinflammatory cytokines and CD4+Foxp3+RORγt+IL-17A+ regulatory T cells, whereas low fiber enhanced anti-inflammatory cytokines and cytotoxic T cells. High fiber enriched microbial taxa associated with IL-17A+RORγt+ regulatory T cells and altered metabolites, including reduced tryptophan and increased short-chain fatty acids and bile acids. Low fiber produced opposite effects. These findings suggest that dietary fiber's effects on colon cancer depends on microbial infection and immune status, emphasizing the need for personalized dietary interventions in colon cancer management. Prevention Relevance: Dietary fiber's impact on colon cancer progression highlights the need for personalized dietary approaches, considering microbial infection and immune status.