In healthy individuals, glutamine is a neutral, nonessential amino acid. Amino acids are critical to humans, since they form the proteins that are the building blocks for many body tissues, including muscles. Glutamine is the most abundant amino acid in our bodies. It performs several important functions in the body, particularly in those that are stressed because of certain diseases or conditions. Glutamine can be added to the body medically by physicians or through dietary supplements that people purchase without prescriptions.
General use
Researchers continue to study glutamine's properties and effects. It is the most plentiful amino acid in the bloodstream and the body continues to produce it unless some sort of stress occurs. Cancer, burns or trauma, excessive exercise, and certain other stressful situations to the body may cause glutamine levels to drop.
Research suggests that when glutamine levels fall and are not replaced, several body functions are affected, particularly within the digestive tract. Glutamine also is considered important to overall immunity, or ability to fight off diseases and infections. In the past few decades, interest has grown for use of glutamine in helping cancer patients. Research continues on using glutamine therapy to help patients with sepsis, burns, trauma, inflammatory bowel disease, acquired immune deficiency syndrome (AIDS), bone marrow transplants, and other potential diseases and conditions.
Some clinical research has reported glutamine aided patients with multiple trauma and burns by helping them fight off infections. It may help AIDS patients put on weight at a much lower cost, and with fewer complications, than human growth hormone. Athletes who overtrain have higher rates of infectious diseases and allergies; it is thought a diet high in glutamine can help improve these athletes' immune functions.
As more people have begun looking for ways to enhance fitness, they have turned to protein supplements.
In 2003, it was reported that more than 1.2 million athletes used some type of performance-boosting supplement. Glutamine is used in the fitness industry as a supplement for bodybuilders who want to reduce muscle breakdown, or for recreational athletes on vigorous training schedules who feel the supplement fuels their immune systems.
Preparations
As a protein, glutamine occurs naturally in some foods, including meat, fish, legumes, peanuts, eggs, tofu, and dairy products. It also is highly concentrated in raw cabbage and beets. Cooking can destroy glutamine, particularly in vegetables. Much of a person's glutamine needs, even when exercising hard, can come from food sources. A 3–oz serving of meat contains about 3–4 grams of glutamine.
Glutamine supplements come in several forms. Some manufacturers sell tablets that also contain antioxidants (vitamins). The most common forms of glutamine supplements are protein powders that can be added to liquids and prepared protein drinks and shakes. Another amino acid called alanine may be combined with glutamine. The combined protein supplement is called alanyl-glutamine. The powder form is probably the most convenient and least expensive form of the supplement. When glutamine is used for medical purposes in a hospital setting, it may be administered via an enteral route, or through a tube directly into the intestine.
In 2002, the powder cost about 10 cents a gram, while the capsules cost between 12 and 23 cents per gram. Capsules deliver fewer grams of glutamine than the powder and the glutamine in capsules does not absorb as quickly as that in powder. The powder reportedly tastes mild and is not noticeable when added to favorite drinks.
Recommended doses of glutamine for fitness uses such as bodybuilding vary, but generally are 8–20 grams (g) a day and average about 15 g a day. Cancer patients on glutamine therapy may take a higher dose, about 30 g a day. An average daily therapeutic dose for the general public is 1.5–6 g.
Precautions
The powdered form of glutamine should be dissolved in a liquid and consumed quickly before it breaks down. Some literature recommends taking glutamine immediately before or after meals, or at the same time as eating protein, usually twice per day.
Glutamine is marketed as a dietary supplement, and therefore, the products are not regulated the same as prescription drugs. Those who take glutamine must be cautioned to carefully read labels; some supplements are not what they appear to be. In 2004, the U.S. Food and Drug Administration (FDA) outlined a new process to try to work toward better safety of the 29,000 dietary supplements on the American market. However, consumers still need to be cautious of contents and claims of dietary supplements. It also is important to follow dosage directions and/or to check with a physician or other certified medical or complementary medicine practitioner to ensure the correct dose is being taken. Finally, while many fitness promoters tout glutamine's effects, some researchers disagree with the science behind the claims. In time, more and larger clinical trails may be able to clear up the controversy over glutamine's ability to increase muscle size and strength in recreational athletes.
Side effects
No noticeable negative side effects of glutamine at recommended dosage and preparations had been reported as of May 2004. However, long-term research is ongoing.
Interactions
As of May 2004, glutamine has not been shown to interact with any particular drugs or with other supplements. However, research on glutamine supplements is limited and ongoing. Consumption of cabbage can worsen goiters and a condition called hypothyroidism. Since glutamine is not a regulated substance, it is best to consult a physician when adding the supplement to the diet and to mention regular glutamine supplementation to a health professional when he or she is treating a patient for a new disease or condition, or adding or changing drug therapy.
PERIODICALS
"Advanced Nutrition: Absorbing Stuff from Team FLEX." Flex (February 2003): 183–191.
Krenkel, Jessica A. "Glutamine Supplementation in Bone Marrow Transplantation (BMT)." Topics in Clinical Nutrition (September 2002): 83–91.
Nick, Gina L. "Impact of Glutamine–rich Foods on Immune Function (Medicinal Properties in Whole Foods." Townsend Letter for Doctors and Nurses (April 2002): 148–157.
"Protein Supplements of Little Use, Says Trial." Nutraceuticals International (May 2001).
"Glutamine." QFAC Bodybuilding [cited June 6, 2004]. <http://www.qfac.com/glutamine.html>.
"Report Offers Science-based Process and Guidelines to Evaluate Safety of Dietary Supplements." The National Academies Press Release. <http://www4.nationalacademies.org>.
