Fueling recovery: evidence-based ICU nutrition and immunonutrition strategies in 2026

Our understanding of the metabolic response to critical illness continues to evolve and delivery of nutrition therapy in the intensive care unit (ICU) has become more nuanced. Both underfeeding and overfeeding have recognized harms, and it is often challenging to provide the right dose at the right time by the right route to the right patient. The historic 'ebb and flow' model of critical illness metabolism has been replaced by a modern model describing early and late acute phase, chronic phase and convalescent phase. Macronutrient delivery should be tailored to not only the patient but also the phase of critical illness. In the absence of contraindications to enteral nutrition (EN), trophic rate EN should begin when acute resuscitation is complete, typically within 48 hours of ICU admission. During the first week or early acute phase of critical illness, energy delivery should be limited to no more than 70%-80% of 'full' nutrition because of the unavoidable presence of endogenous glucose production. Similarly, protein delivery should be limited to ≤1.2 g/kg/day. After the early acute phase, both energy and protein prescription should increase to 100% 'full' nutrition and 1.2-2.0 g/kg/day. In the chronic convalescent and post-ICU phase, even higher energy and protein prescriptions may be necessary to regain lost muscle mass and function. Early physical therapy or neuromuscular stimulation is safe, feasible and likely beneficial. Although intravenous glutamine and arginine are no longer recommended, there may be a role for intravenous fish oil and enteral glutamine (only for burns >20% Total Body Surface Area (TBSA)).