From Catabolism to Recovery: Optimizing Nutrition in Critically Ill Adults

Abstract

Introduction: Nutrition is a critical component of care for critically ill adult patients, influencing morbidity, mortality, and recovery in intensive care units (ICUs).
Objective: To summarize current evidence on nutritional requirements, interventions, and clinical outcomes in adult ICU patients, highlighting strategies to optimize recovery and reduce complications.
Methods: A comprehensive narrative review with a systematic literature search of PubMed, Embase, Cochrane Library, and Web of Science (2010–2025) was conducted. Included studies comprised randomized controlled trials, observational cohorts, meta-analyses, and guidelines reporting nutritional interventions and outcomes in adult ICU populations. Studies on pediatric patients, non-ICU settings, or non-peer-reviewed sources were excluded. Data on type and timing of nutritional support, caloric and protein targets, micronutrient supplementation, and clinical outcomes (mortality, ICU length of stay, infections, mechanical ventilation duration) were extracted.
Results: Seventy-two studies met inclusion criteria. Early enteral nutrition (within 24–48 hours) and protein intake of 1.2–2.0 g/kg/day improved nitrogen balance, reduced muscle wasting, shortened mechanical ventilation duration, and decreased ICU-acquired infections. Micronutrient supplementation (vitamins D, C, thiamine; selenium, zinc) and immunonutrition (arginine, omega-3 fatty acids, nucleotides) showed promising but variable effects, particularly in surgical and trauma patients. Overfeeding was associated with hyperglycemia and hepatic steatosis, while underfeeding correlated with catabolism and poor functional recovery. Nutritional risk assessment using APACHE II, NUTRIC, or mNUTRIC scores enabled individualized interventions.
Conclusions: Early, individualized nutrition is central to ICU care. Multidisciplinary coordination improves outcomes. Future research should address precision nutrition, long-term recovery, and metabolic monitoring.