Glutamine is a nonessential amino acid with a major role in maintaining the integrity of the GI tract lining, especially during the hypermetabolic phase of the stress response (abnormally increased metabolism); also seen during fever and some forms of poisoning; repairs the collagen and strengthens the fibers between the holes in the GI tract lining. A precursor for the relaxing neurotransmitier, GABA, glutamine stabilizes blood sugar flow, reduces cravings for alcohol, enhances immunity, preserves lean body mass during weight loss and athletic activity, and, with FOS, provides nutrients to GI tract cells (enterocytes).

L-glutamine is a protein amino acid found in proteins of all life forms. It is classified as a semi-essential or conditionally essential amino acid. This means that under normal circumstances the body can synthesize sufficient L-glutamine to meet physiological demands. However, there are conditions where the body cannot do so. Recently, it has come to be regarded as one of the most important of the amino acids when the body is subjected to such metabolic stress situations as trauma (including surgical trauma), cancer, sepsis and burns. Under such conditions, this amino acid becomes an essential amino acid, and it is therefore very important to ensure adequate intakes of the amino acid in order to meet the increased physiological demands created by these situations.

This product is the most abundant amino acid in the body, and plasma glutamine levels are the highest of any amino acid. It is predominantly synthesized and stored in skeletal muscle. The amino acid L-glutamate is metabolized to L-glutamine in a reaction catalyzed by the enzyme glutamine synthase, a reaction which, in addition to L-glutamate, requires ammonia, ATP and magnesium.

This supplement is a very versatile amino acid and participates in many reactions in the body. It is important in the regulation of acid-base balance. It allows the kidneys to excrete an acid load, protecting the body against acidosis. This is accomplished by the production of ammonia, which binds hydrogen ions, to produce ammonium cations that are excreted in the urine along with chloride anions. Bicarbonate ions are simultaneously released into the bloodstream. This amino acid helps protect the body against ammonia toxicity by transporting ammonia, in the form of L-glutamine's amide group, from peripheral tissues to visceral organs, where it can be excreted as ammonium by the kidneys or converted to urea by the liver.

The amide group can also participate in other metabolic activities, as can the amino group of L-glutamine. It serves as the most important nitrogen shuttle, supplying nitrogen for metabolic purposes (from glutamine-producing tissues, such as skeletal muscle) to glutamine-consuming tissues.

This nutrition participates in the formation of purine and pyrimidine nucleotides, amino sugars (such as glucosamine), L-glutamate and other amino acids, nicotinamide adenine dinucleotide and glutathione. It also participates in protein synthesis, energy production and, if necessary, the production of D-glucose and glycogen. Importantly, it can serve as the primary respiratory substrate for the production of energy in enterocytes and lymphocytes. L-glutamine is considered an immunonutrient, and supplemental L-glutamine is used in medical foods for such stress situations as trauma, cancer, infections and burns.

L-glutamine is also known as 2-aminoglutaramic acid, levoglutamide, (S)-2, 5-diamino-5-oxopentaenoic acid and glutamic acid 5-amide. Its one-letter abbreviation is Q, and it is also abbreviated as Gln. The terms L-glutamine and glutamine are used interchangeably. D-glutamine, the stereoisomer of L-glutamine, does not have, as far as is known, biological activity. L-glutamine is not very soluble in water, and aqueous solutions are unstable at temperatures of 22 to 24 degrees Celsius. For these reasons, the more soluble and more stable glutamine dipeptides are used as delivery forms of L-glutamine in total parenteral nutrition (TPN) solutions. See Glutamine Peptides.