Glutamine and Immune System Support

Glutamine is considered an essential amino acid during stress and critical illness which means that the human body cannot synthetize enough of glutamine to satisfy the needs or rapidly proliferating cells of the immune system, especially in the gut. Partial glutamine deficiency is considered an independent risk factor of mortality in patients after a major operation (which is of course a major stress to the body).

Even in otherwise healthy people in situations of extreme stress, such as heavy exercise, viral or bacterial infections, the concentration of glutamine in the blood diminishes. In many athletes, both recreational and professional, this decrease occurs concomitantly with relatively transient immune-depression and might be worsened by mild infections which are often untreated (Field CJ et al. Glutamine and arginine: immunonutrients for improved health. Med Sci Sports Exerc. 2000;32(7S):S377-S388). Since glutamine is used as a fuel by rapidly proliferating cells of the immune system, oral intake of glutamine has been seen to have a beneficial effect on gut function, on morbidity and mortality, and on some aspects of immune cell function in clinical studies (Castell L., Glutamine supplementation in vitro and in vivo, in exercise and in immune-depression. Sports Med. 2003;33(5):323-345). It has also been seen to decrease the self-reported incidence of illness, probably through its action on neutrophils (Rohde T et al. The immune system and serum glutamine during a triathlon. Eur J Appl Physiol Occup Physiol. 1996;74(5):428-434). Another possible mode of action is a glutamine-induced increase of the lymphocyte count and concomitant decrease in lipid peroxidation (Cavalcante AA et al. Enteral nutrition supplemented with L-glutamine in patients with systemic inflammatory response syndrome due to pulmonary infection. Nutrition. 2012;28(4):397-402). Finally, it also needs to be noted that glutamine is one of the three amino acids involved in glutathione synthesis and it serves as a precursor for the production of arginine through the citrulline-arginine pathway. Those pathways may be contributing to overall beneficial effects of glutamine supplementation. Glutathione, an important intracellular antioxidant and hepatic detoxifier may also be one of the reasons of protective effects of glutamine in stress and immune-depression.

Most of the clinical knowledge on glutamine effects in stress and strenuous exercise are derived from its medical applications after infections and/or in difficult post-operative states (García-de-Lorenzo A et al. Clinical evidence for enteral nutritional support with glutamine: a systematic review. Nutrition. 2003;19(9):805-811). In those situations, glutamine has been applied at relatively high doses of 20 – 30 gram and reportedly improved survival of the patients and lowered both time and costs of medical treatments (Gianotti L et al. Oral glutamine decreases bacterial translocation and improves survival in experimental gut-origin sepsis. JPEN J Parenter Enteral Nutr. 1995;19(1):69-74 and Al Balushi RM et al. The clinical role of glutamine supplementation in patients with multiple trauma: a narrative review. Anaesth Intensive Care. 2013;41(1):24-34).

Stresses of daily life are much less damaging that the life-threatening post-operative states, yet the neuro-endocrine-immune responses are qualitatively similar. Thus, as already mentioned athletes and otherwise healthy subjects under stress, clearly benefit from provision of glutamine due to stimulated immune system and enhanced functionality of immune cells in the gut (Akagi R et al., Glutamine protects intestinal barrier function of colon epithelial cells from ethanol by modulating Hsp70 expression. Pharmacology. 2013;91(1-2):104-111). Such an effect invariably leads to lower rates of infections and contributes to maintaining the health of the mucosa (inner wall) of the gastrointestinal tract.

Finally, healthy adults take app. 5 – 9 gram glutamine from daily diet and supplemental glutamine is considered safe when used in accordance with proper dosing.