The immunologic role of the gastrointestinal tract.

During the past few decades, researchers have shed new light on the role of nutritional support in the immunocompromised critically ill patient. "Nutritional pharmacology" has become the catch phrase of the 1990s due to the impact of selected nutrients on host immune defenses. When feasible, enteral nutrition is preferred to parenteral nutrition to preserve the integrity of the gut mucosal barrier, especially when administered jejunally in the early stages of hypermetabolism. Glutamine and fiber provide necessary fuels for the gastrointestinal tract, whereas arginine and omega-3 fatty acids exert beneficial effects on certain cells of the immune system. Daly et al demonstrated that "enteral nutrition with supplemental arginine, RNA nucleotides and omega-3 fatty acids (Impact, Sandoz Nutrition, Minneapolis, MN) compared with a standard enteral diet, significantly improved immune, metabolic and clinical outcomes (22% mean reduction in length of stay) in UGI cancer patients undergoing surgery." Although more research is needed in the area of nutritional pharmacology, newly available nutrient-specific enteral products (Table 1) provide promise for altering the clinical outcome of immunocompromised patients.