Glutamine is the most abundant naturally occurring non-essential amino acid in the body and is one of the 20 amino acids encoded by the standard genetic code. It is not recognized as an essential amino acid, but is becoming conditionally essential in intensive athletic training or certain gastrointestinal disorders. In the body, glutamine is found circulating in the blood and stored in the skeletal muscles. It becomes conditionally essential to the body (requiring intake from food or supplements), when a indvidual develops illness or injury.
Glutamine is synthesized by the enzyme glutamine synthetase from glutamate and ammonia. Accounting for about 90% of all glutamine synthesized, muscle mass is the most relevant glutamine-producing tissue. Glutamine is also released, in small amounts, by the lung and the brain.
Glutamine is also known to assist in operations, reducing the healing time upon completion of the procedure. Clinical trials have show that patients on glutamine supplementations have improved nitrogen balances and also improved lymphocyte recovery and intestinal permeability (in postoperative patients), in comparison to those that had no glutamine within their diet.