Dietary Fiber Structural Diversity Shapes Gut Microbiome Function: A Glycocentric Perspective

Abstract Dietary fibers comprise structurally diverse, non-digestible glycans that escape hydrolysis and absorption in the upper gastrointestinal tract and reach the colon, where they serve as key substrates for gut microbial communities. In the colon, these glycans are enzymatically deconstructed and anaerobically fermented into metabolites that play central roles in host physiology. The glycan biochemical code─defined by monosaccharide composition, glycosidic linkages, and substitution patterns─determines the enzymatic repertoires required for microbial utilization. Beyond composition, multiscale supramolecular architecture governed by non-covalent and covalent interactions further modulates physical accessibility and microbial degradation. Together, these structural features shape the spatial and temporal organization of the gut microbiota, driving networks of microbial specialization, competition, and cooperation. This Perspective proposes a glycocentric framework, positioning glycan biochemical diversity and multiscale structure as primary determinants of microbiome function. We further propose structural metrics for dietary fiber reporting in microbiome and intervention studies to enable mechanistic and reproducible investigations of fiber–microbiome interactions. Tailoring fiber architectures to individual microbial capacities could provide a strategy to steer microbial ecology and improve metabolic health outcomes. Realizing this potential will require a mechanistic understanding of dietary fiber utilization in situ across spatial and temporal scales.