<![CDATA[Background: Critically ill patients frequently develop gut dysbiosis, characterized by reduced microbial diversity and increased colonization by opportunistic pathogens. These alterations may contribute to gastrointestinal dysfunction and are associated with small intestinal bacterial overgrowth (SIBO)-related outcomes. Enteral nutrition is a key nutritional strategy for critically ill patients and may influence gut microbiota composition; however, its role in modulating the microbiota and its implications for SIBO-related outcomes remain unclear.Objectives: This systematic review aimed to synthesize evidence on the relationship between enteral nutrition and gut microbiota modulation in critically ill adults and explore its potential implications for SIBO-related gastrointestinal outcomes.Methods: A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA 2020) guidelines and registered in the PROSPERO database (CRD420261384432). Literature searches were performed in PubMed and Google Scholar for studies published between 2020 and 2026. Observational studies and randomized controlled trials involving critically ill patients receiving enteral nutrition, with outcomes related to the gut microbiota, gastrointestinal function, or SIBO were included. Data were extracted and synthesized narratively and thematically. Results: Seven studies were included in the meta-analysis. Evidence from studies directly assessing microbiota has demonstrated reduced microbial diversity and increased abundance of opportunistic pathogens during critical illness. Studies evaluating fiber- or prebiotic-containing enteral formulas suggested potential increases in short-chain fatty acid (SCFA)-producing bacteria, although the findings remained inconsistent and were influenced by antibiotic exposure and clinical severity. Only one of the included studies directly evaluated SIBO.Conclusion: Enteral nutrition may influence the gut microbiota composition in critically ill patients; however, direct evidence regarding SIBO remains limited. Further prospective studies using standardized microbiota and SIBO assessment methods are needed before the clinical implications for nutritional practice can be more clearly established.]]>
