Glutamine is a non-essential amino acid present abundantly throughout the body and is involved in many metabolic processes. It is synthesized from glutamic acid and ammonia. It is the principal carrier of nitrogen in the body and is an important energy source for many cells. Supplemental L-glutamine's possible immunomodulatory role may be accounted for in a number of ways. L-glutamine appears to play a major role in protecting the integrity of the gastrointestinal tract and, in particular, the large intestine. During catabolic states, the integrity of the intestinal mucosa may be compromised with consequent increased intestinal permeability and translocation of Gram-negative bacteria from the large intestine into the body. The demand for L-glutamine by the intestine, as well as by cells such as lymphocytes, appears to be much greater than that supplied by skeletal muscle, the major storage tissue for L-glutamine. L-glutamine is the preferred respiratory fuel for enterocytes, colonocytes and lymphocytes. Therefore, supplying supplemental L-glutamine under these conditions may do a number of things. For one, it may reverse the catabolic state by sparing skeletal muscle L-glutamine. It also may inhibit translocation of Gram-negative bacteria from the large intestine. L-glutamine helps maintain secretory IgA, which functions primarily by preventing the attachment of bacteria to mucosal cells. L-glutamine appears to be required to support the proliferation of mitogen-stimulated lymphocytes, as well as the production of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma). It is also required for the maintenance of lymphokine-activated killer cells (LAK). L-glutamine can enhance phagocytosis by neutrophils and monocytes. It can lead to an increased synthesis of glutathione in the intestine, which may also play a role in maintaining the integrity of the intestinal mucosa by ameliorating oxidative stress. The exact mechanism of the possible immunomodulatory action of supplemental L-glutamine, however, remains unclear. It is conceivable that the major effect of L-glutamine occurs at the level of the intestine. Perhaps enteral L-glutamine acts directly on intestine-associated lymphoid tissue and stimulates overall immune function by that mechanism, without passing beyond the splanchnic bed. Glutamine is used for nutritional supplementation, also for treating dietary shortage or imbalance.

Alanyl-glutamine is a widely used alternative supplement to L-glutamine in the production of biopharmaceuticals. The primary advantage of using L-alanyl-glutamine in place of L-glutamine is that it reduces the level of ammonia generated during cell culture. L-alanyl glutamine also acts as an antioxidant (peroxide) and anti-apoptosis (LPS-induced) factor. Ala-Glu may be used in cell culture and insect cell culture applications. It can be used in studies on injury and sepsis, and in the effects of irradiation on leucine and protein metabolism in vivo. Alanyl-glutamine is used as dipeptide infusion solution, which is given as part of parenteral and/or enteral nutritional therapy. When the intake of nutrients or food into the mouth or directly into the gut is not possible or it is not enough to supply the body’s needs then nutrients or foods can be given intravenously or through the gastrointestinal tract or a combination of both. This is especially important for people whose bodies are under physical stress from illness or recent surgery. During illness or after surgery the body requires nutrition or food. Amino acids are the building blocks used by the body to make proteins. Dipeptiven is usually given as a supplement to amino acid solutions or an amino acid containing infusion regimen as part of complete nutritional support.