Glutamine is the most abundant amino acid (protein building block) in the body and is involved in more metabolic processes than any other amino acid. Glutamine is converted to glucose when more glucose is required by the body as an energy source. It serves as a source of fuel for cells lining the intestines. Without it, these cells waste away. It is also used by white blood cells and is important for immune function. In animal research, glutamine has anti-inflammatory effects. Glutamine in combination with N-acetyl cysteine promotes the synthesis of glutathione, a naturally occurring antioxidant that is believed to be protective in people with HIV infection. Evidence indicates that intravenous glutamine supplementation increases the survival rate of critically ill people.

Glutamine is one of the twenty amino acids generally present in animal proteins. A monoamide of glutamic acid, the biochemical is also a component of many plants and was first isolated from beet juice in 1883. Glutamine was not isolated as a component from a protein, however, until 1932 and was first chemically produced the following year. The substance plays an important role in the cellular metabolism of animals and is the only amino acid with the ability to easily cross the barrier between blood and brain tissue. Combined, glutamine and glutamic acid are responsible for the vast majority of the amino nitrogen located in the brain, and are of central importance in the regulation of bodily ammonia levels. Though it is readily synthesized naturally within the body, glutamine is popularly sold as a nutritional supplement for athletes.

Glutamine is a nonessential amino acid. Only the L form of amino acids are constituents of protein. Glutamine is essential for DNA synthesis, cellular energy, growth and repair. It is used by white blood cells to support the immune system.

Few healthy people are glutamine deficient, in part because the body makes its own. During fasting, starvation, cirrhosis, critical illnesses in general, and weight loss associated with AIDS and cancer, however, deficiencies often develop.

No significant side effects have been reported in glutamine studies.

Glutamine is found in many foods high in protein, such as fish, meat, beans, and dairy products.