Nutritional support in immunosuppressed critically ill patients

Immunosuppressed patients now make up a growing share of intensive care unit (ICU) admissions, largely as a result of advances in cancer treatment, organ transplantation, and immunomodulatory therapies. While their short-term ICU mortality may be similar to that of immunocompetent patients when illness severity is taken into account, these individuals often face longer ICU stays, more complications, and poorer long-term outcomes. In this context, artificial nutrition plays a central role in ICU management and represents a potentially modifiable intervention. Beyond meeting energy requirements, nutritional support may help sustain immune function, preserve gut integrity, and reduce the risk of infectious complications. Whenever possible, enteral nutrition should be favored, as it supports the intestinal barrier and gut-associated lymphoid tissue, even when delivered at low, trophic doses. Parenteral nutrition remains indispensable in the presence of intestinal failure but should be used cautiously, given its association with complications such as catheter-related bloodstream infections. Critical illness profoundly alters gut-immune interactions, promoting dysbiosis, increased intestinal permeability, and immune dysfunction - processes that may be further amplified by immunosuppressive therapies. This has fueled interest in immunonutrition strategies, including arginine, ω-3 fatty acids, glutamine, and nucleotides. However, evidence in immunosuppressed critically ill patients remains limited and inconsistent, preventing firm recommendations. Looking ahead, the integration of body composition assessment, immune-metabolic phenotyping, multi-omics technologies, and artificial intelligence may enable more personalized nutritional strategies. Future studies should focus on phenotype-specific randomized trials to better define the optimal route, composition, timing, and dosing of nutritional support in this complex population.