Soluble, Insoluble, and Mixed Rice Bran Dietary Fibers Generate Distinct Host-Microbiota-Metabolome Responses in DSS-Induced Colitis.

Rice bran dietary fiber comprises soluble and insoluble fractions, but their differential host, microbial, and metabolic effects remain unclear. We compared RB-SDF, RB-IDF, and their mixture (RB-MIX) at two doses in DSS-induced colitis. All formulations alleviated symptoms, histological injury, barrier dysfunction, endotoxemia, and inflammation, but their relative advantages varied by end point and dose. RB-SDF showed histological protection and the greatest high-dose SCFA output, whereas RB-IDF produced distinct benefits for barrier-related and metabolic end points. RB-MIX remained effective but did not consistently match or exceed the strongest responses of the individual fractions. Microbiota profiling and untargeted metabolomics revealed formulation-dependent remodeling rather than uniform restoration. Disease-axis and factorial analyses further revealed partial shifts toward the CONTROL-associated metabolic profile and substantial contributions of fiber formulation and the formulation-by-dose interaction. These findings support the rational selection and formulation of rice bran fiber ingredients for functional foods.