Glutamine and its metabolites are important for the production and optimal activity of hexosamine biosynthetic pathway. The role of amino acids, especially glutamine, has been recognized in cell defense mechanisms, through impact on antioxidant properties. In vitro studies with various cell types, such as muscle cells, intestinal mucosa, cells of the immune system, specific neurons of the central nervous system, hepatocytes, pancreatic ß-cells, and others, have demonstrated that L-glutamine is required in the incubation medium for growth and normal function. Enteral nutritional solutions with L-glutamine supplementation are important to tissues other than the gut. It is important to note that L-glutamine supplementation may not prevent inflammation, damage, disease, or even enhance performance but may help the recovery of cells under severe catabolic situations, enhancing cell defenses, attenuating apoptosis and uncontrolled inflammatory response. If the condition is diagnosed early and managed appropriately, providing optimal supplementation and nutritional support, patient outcomes can be improved.