Gastrointestinal tract is an organ for digestion, absorption and utilization of nutrients. Also it functions as an immunological organ in the human body. Patients with gastrointestinal disease are at increased risk for nutritional problem due to dietary restriction during the treatment or diagnostic examinations, anorexia or altered nutritional requirement. Clinically, it is important for gastroenterologists to be aware of the principles of nutritional therapy and the relationship between gastrointestinal diseases and the combined nutritional abnormalities. Removal of enteral feeding causes mucosal atrophy and leads to increased mucosal permeability to bacteria and endotoxin. The intestinal endotoxemia results from the translocation of bacteria and endotoxin to systemic circulation, may triggers off systemic inflammatory response syndrome. Therefore, it is crucial in critically ill patients to maintain the gastrointestinal mucosal integrity along with the intestinal flora that enables the host immunity to be maintained or enhanced. Immunonutrition is a therapeutic approach to enhance the gastrointestinal mucosal barrier with various specific nutrients. The intestinal endotoxemia and immunonutrition will also be reviewed briefly.