Optimizing Perioperative Nutrition in Elective Gastrointestinal Surgery: An ERAS-Focused Narrative Review

Background/Objectives: Perioperative malnutrition, sarcopenia, and reduced functional reserve are frequent in adults undergoing elective gastrointestinal (GI) surgery and are associated with higher postoperative morbidity and delayed recovery. Enhanced Recovery After Surgery (ERAS) pathways incorporate nutrition-focused elements, but reported effects vary across procedures, protocols, and baseline risk. This review aims to summarise and critically appraise current evidence on perioperative nutritional strategies within ERAS-focused elective GI care, including risk identification, nutritional prehabilitation (oral nutritional supplements and immunonutrition), preoperative carbohydrate loading, early postoperative feeding, and selected microbiome-directed adjuncts. Methods: This narrative literature review was informed by a focused search of PubMed/MEDLINE and Scopus (2010–2025), supplemented by targeted screening of relevant clinical practice guidelines and consensus statements (e.g., ESPEN). Evidence was interpreted by hierarchy (guidelines/meta-analyses, randomised trials, observational studies) and discussed with attention to heterogeneity in surgical populations, intervention definitions (composition, timing, duration), and endpoint reporting. Results: Early nutritional risk screening is consistently supported to identify malnutrition and sarcopenia and to trigger tailored optimisation plans. Perioperative oral nutritional supplementation, particularly when started preoperatively and continued postoperatively, is frequently associated with improved intake and reduced infectious morbidity in malnourished or at-risk patients, though effect sizes vary. Immunonutrition shows potential benefit in selected high-risk settings but remains formulation- and timing-dependent. Carbohydrate loading is generally endorsed within ERAS and may reduce insulin resistance and improve patient comfort, while impacts on major clinical outcomes are context-dependent. Early oral/enteral feeding is feasible in many elective GI procedures and may accelerate gastrointestinal recovery without increasing major complications when implemented with structured advancement and appropriate patient selection. Probiotics/synbiotics show the most consistent signals in colorectal surgery, with strain-specific effects and important safety boundaries in immunocompromised or critically ill patients. Conclusions: Perioperative nutritional optimisation is a core component of elective GI surgical care within ERAS pathways. Benefits are most reproducible in higher-risk patients and when interventions are integrated into high-compliance multidisciplinary programmes. Future research should prioritise procedure-specific, risk-stratified trials with standardised interventions and clinically meaningful endpoints.