L-Glutamine is the most abundant and utilized amino acid in the body. Considered conditionally essential, glutamine is widely used by the body to provide nitrogen and fuel to rapidly dividing cells. Glutamine is a precursor to a variety of biologically active molecules and acts as a substrate in immune responses.(1- 2) Glutamines use and function is of the utmost importance in a high metabolic state where the need goes beyond the production of the body.(2) For this reason, glutamine has long been used as a nutritional supplement. Originally touted by the fitness industry for its ability to improve muscle building, glutamine research has expanded this nutrient's known benefit to impact: gut inflammation and integrity; improved outcomes in cancer and critically ill patients, infection control in surgical patients and athletes, performance in endurance athletes in addition to wound healing.(3-18)

Leaky Gut Syndromes

The intestinal barrier provides a key first line protective role for the body that goes well beyond the gut.(5) When this barrier is compromised, a hyperpermeable gut can underlie or worsen a multitude of conditions and disease states including: inflammatory bowel disease, irritable bowel syndromes, chronic inflammatory diseases, skin conditions, hepatic conditions and chronic fatigue.(6) One of the mechanisms theorized to contribute to these disorders is related to the immune response that ensues from a compromised gut causing an onslaught of food hypersensitivities.(6) As the preferred fuel for enterocytes, L-glutamine has proven to be effective in reducing permeability and preserving mucosal integrity by promoting the turnover of these cells.(7) This can re-establish those tight intestinal cellular junctions and promote healing of larger gut lesions.(7) Further, in induced experimental colitis, glutamine has been shown to reduce the inflammatory injury in the gut caused by the immune process in this disease.(8)

Cancer and Critical Illness

In circumstances of ongoing stress from critical illness the utilization and need for glutamine increases substantially. Glutamine becomes conditionally essential to fuel enterocytes, immune cells and to maintain acid-base balance through the kidneys.(9,10) Specifically, it has been found to maintain the intestinal barrier and reduce the risk of infection.(11) Added sources from the diet or supplementation have been shown to improve clinical outcomes.(9-12) Cancer is considered a hypermetabolic state in which the resulting glutamine deprivation can contribute to organ dysfunction and ultimate decline.(12) Review of experimental and clinical evidence suggests that enteral glutamine supplementation can support the cancer patient's metabolism, delay cachexia and organ failure, reduce complications of harsh therapies, and improve prognosis without promoting tumour growth.(12)

Burns and Complex Wounds

Severe burns and wounds are also considered a catabolic state in which muscular wasting, weight loss and infection occur. In these states, glutamine extracted from muscle tissue plays a major role in immune defences, organ function and wound repair.(13) Limited by the body's supply, supplementation with glutamine has been shown to improve gut permeability and enhance immune cell function leading to a decrease in infection rates, reduced healing time and shortened hospital stays.(14,15) Beyond burns, these beneficial effects have also transferred to elective surgeries and other major injuries.(13)

Endurance Exercise

Intense and prolonged physical exercise can cause issues ranging from dehydration effects to immunosuppression and overtraining fatigue.(16-18) After high-level endurance training, plasma glutamine levels are depressed in addition to total lymphocytes(16) and ammonia is increased.(17) These outcomes contribute to increased risk of infection post activity(16), peripheral and central fatigue(17). Clinical trials comparing glutamine administration to control found glutamine was able to mitigate some of these stress effects. It also reduced blood accumulation of ammonia.(17) In those with depleted hydration, glutamine positively affected fluid and electrolyte uptake, which increased time to exhaustion.(18) It also had an immunostimulatory effect and reduced the amount of subsequent infections post activity.(16)