The study investigates the impact of dietary fiber on colitis sensitivity, focusing on the individualized effects of specific soluble fibers (inulin and psyllium) on the intestinal microbiota. Using an in vitro microbiota modeling system (MiniBioReactor Array, MBRA), the researchers observed significant inter-individual variation in the responsiveness of different microbiotas to these fibers. Some microbiotas showed dramatic changes in composition, pro-inflammatory potential, and metabolomic profile, while others were minimally affected. Mice transplanted with fiber-sensitive microbiotas exhibited colitis highly modulated by soluble fiber consumption, whereas those with fiber-resistant microbiotas displayed colitis severity regardless of fiber exposure. The study concludes that the impact of soluble fibers on colitis susceptibility is highly influenced by an individual's microbiota composition, suggesting that personalized fiber-based interventions could be beneficial for both IBD patients and healthy individuals.The study investigates the impact of dietary fiber on colitis sensitivity, focusing on the individualized effects of specific soluble fibers (inulin and psyllium) on the intestinal microbiota. Using an in vitro microbiota modeling system (MiniBioReactor Array, MBRA), the researchers observed significant inter-individual variation in the responsiveness of different microbiotas to these fibers. Some microbiotas showed dramatic changes in composition, pro-inflammatory potential, and metabolomic profile, while others were minimally affected. Mice transplanted with fiber-sensitive microbiotas exhibited colitis highly modulated by soluble fiber consumption, whereas those with fiber-resistant microbiotas displayed colitis severity regardless of fiber exposure. The study concludes that the impact of soluble fibers on colitis susceptibility is highly influenced by an individual's microbiota composition, suggesting that personalized fiber-based interventions could be beneficial for both IBD patients and healthy individuals.