Postbiotics: Novel Modulators of Gut Health, Metabolism, and Their Mechanisms of Action.

Postbiotics, defined as non-viable microbial cells, structural components, or metabolites, have recently emerged as promising modulators of gut health and metabolism. Unlike probiotics, they circumvent safety concerns associated with live microorganisms, including potential translocation, antibiotic resistance transfer, and viability loss during storage. Postbiotics encompass diverse bioactive compounds such as short-chain fatty acids (SCFAs), exopolysaccharides, bacteriocins, antioxidant enzymes, surface layer proteins, and bacterial lysates, each exerting distinct biological effects. Mechanistically, they enhance epithelial barrier function, regulate innate and adaptive immune responses, and modulate host gene expression through pattern recognition receptors and epigenetic modifications. SCFAs, particularly butyrate and propionate, improve intestinal homeostasis, insulin sensitivity, and anti-inflammatory signaling, while bacteriocins and EPSs display antibacterial, antiviral, anticancer, and immunomodulatory properties. Postbiotics also interfere with viral replication, inhibit pathogen adhesion, and attenuate inflammatory pathways, highlighting their multifunctional roles. Compared to probiotics and prebiotics, they offer superior safety, chemical stability, and clinical applicability, especially in vulnerable populations such as infants, elderly individuals, and immunocompromised patients. Preclinical and in vitro studies provide compelling evidence for their therapeutic potential in metabolic disorders, infections, cancer, and immune-mediated diseases; however, clinical data remain limited. Further research is required to establish standardized definitions, optimal formulations, dosing strategies, and regulatory frameworks to support their integration into functional nutrition and precision medicine. Collectively, postbiotics represent a next-generation approach to microbiota-targeted interventions, offering novel opportunities for disease prevention, adjunctive therapy, and the advancement of microbiome-based therapeutics.