Immunonutrition and critical illness: an update

Dietary supplementation with nutrients that have physiologic effects on immune function has been shown to be beneficial in subsets of patients with surgical and medical critical illness. However, several meta-analyses have suggested potential harm when immune nutrients are used inappropriately. This has led to concern among clinicians that in turn has curtailed the more widespread use of immunonutrition as a therapeutic modality. This article discusses the mechanisms by which immune nutrients can be used to modulate alterations in innate and acquired immunity associated with critical illness. In addition, recent evidence-based clinical practice guidelines for use of immunonutrition in adults is reviewed as a means to clarify some of the more controversial issues and provide a "roadmap" for the practitioner.