Review: Nutritional Support in Critically Ill Patients

Introduction: This summary is derived from a state-of-the-art review on nutritional support in the intensive care unit (ICU) published in The BMJ. Critically ill patients experience metabolic disturbances, inflammation, and profound muscle wasting. Nutritional therapy aims to mitigate these effects, though recent randomized controlled trials (RCTs) challenge the dogma of early, aggressive provision of high-calorie and high-protein diets for all ICU patients. Instead, emerging evidence indicates that moderate energy and protein restriction, particularly during the first week, may enhance recovery and reduce complications such as hospital-acquired infections, muscle weakness, and ICU-acquired morbidity. Nonetheless, identifying ideal feeding strategies remains complex, given the dynamic nature of critical illness and the interplay with other interventions such as sedation and physical rehabilitation.

Key Recommendations:

1. Individualized Timing and Dose: Limit caloric and protein loads during the acute phase (roughly the first seven days), especially in patients with hemodynamic instability or shock. Later, as patients transition to recovery, gradually increase macronutrient delivery to meet evolving metabolic needs.
2. Preferred Feeding Route: Enteral nutrition is generally recommended when the gastrointestinal tract is functional, particularly after shock resolution. Parenteral nutrition can be reserved for prolonged gut dysfunction or inability to meet needs enterally. Studies comparing enteral versus parenteral feeding have shown no clear outcome differences, but early enteral feeding is often favored for physiological and cost reasons.
3. Avoid Overfeeding and Overzealous Protein Provision: Several large RCTs (including EFFORT-Protein, EDEN, and NUTRIREA-3) observed no mortality benefit—and in some instances, worse outcomes—when patients received full or high doses of energy and protein in the first week. Metabolic “resistance” and inhibition of protective processes such as autophagy might explain why restricted early feeding sometimes confers advantages.
4. Monitoring and Assessment: Traditional tools (NUTRIC, NRS-2002) and biomarkers (albumin, prealbumin) do not reliably predict who benefits from higher or lower feeding levels. Ultrasound or computed tomography to assess muscle mass may hold promise, but no validated approach exists to guide individualized macronutrient targets.
5. Micronutrients and Specialized Formulations: Broad-spectrum pharmaconutrients (glutamine, antioxidants, etc.) have not improved outcomes in well-powered trials. Instead, standard vitamin and trace element supplementation consistent with recommended daily allowances appears sufficient in most cases.
6. Long-term Rehabilitation: Combined nutritional support and physical exercise are critical for mitigating long-term impacts of ICU-acquired weakness and functional decline. Evidence increasingly highlights the need for prolonged, structured rehabilitation to optimize muscle recovery and quality of life.

Conclusion: Although nutritional support remains central to critical care, it is most effective when carefully adapted to disease phase, patient comorbidities, and evolving organ dysfunction. Key evidence suggests a more conservative approach to energy and protein during the acute phase, followed by gradual escalation and integration with rehabilitation. Ongoing research seeks to identify physiological markers that distinguish when to intensify nutritional therapy and how best to align macronutrient delivery with other therapies to promote muscle function and reduce complications.

Reference: Reignier J, Rice TW, Arabi YM, Casaer M. Nutritional Support in the ICU. BMJ. 2025;388:e077979. DOI: https://doi.org/10.1136/bmj-2023-077979