The Role of Different Dietary Fibers in Modulating Human Gut Microbiota

Dietary fiber (DF) has a profound influence on human health mainly by modulating the gut microbiota. This review provides an overview of DF derived from cereals, legumes, fruits, vegetables, fungi, and seaweeds, specifically addressing the relationship between microbial utilization and source-specific structural characteristics (such as linking patterns, conformation, solubility, and fermentability). Due to these structural properties, different DFs display selective microbial responses that favor fermentation and the production of short-chain fatty acids (SCFAs). These microbial responses and fermentation-derived metabolites associated with DF intake may contribute to reduced risk of obesity, diabetes, inflammatory bowel disease, and other chronic disorders. This review does not address the trial heterogeneity, dose response, safety, and conflicting evidence, and much of the available evidence is largely observational and heterogeneous. Future studies should focus on dose–response trials of defined DF structures with standardized microbiome and metabolomic endpoints, including validation in human interventions. This review summarizes the DF source and structure, selective changes in the microbiota across various study types, including in vitro, animal models, and human studies, and how these relate to overall health.