What is it?
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.
Where is it found?
Glutamine is found in many foods high in protein, such as fish, meat, beans, and dairy products.
What do the advocates say?*
Glutamine is the most utilized amino acid in the body. Based on its biochemistry, glutamine is a good supplement for athletes. Glutamine is best taken consistently, on a daily basis, rather than just before or after a hard workout, to build up tissue levels.
Although glutamine is inexpensive and non-toxic, realize that you run the risk of upsetting the balance of the body’s amino acids (as is the case with supplementing with only one of any of the amino acids.
How much is usually taken by athletes?
The amino acid glutamine appears to play a role in several aspects of human physiology that might benefit athletes, including their muscle function and immune system.1 Intense exercise lowers blood levels of glutamine, which can remain persistently low with overtraining.2 Glutamine supplementation raises levels of growth hormone at an intake of 2 grams per day,3 an effect of interest to some athletes because of the role of growth hormone in stimulating muscle growth,4 and glutamine, given intravenously, was found to be more effective than other amino acids at helping replenish muscle glycogen after exercise.5 However, glutamine supplementation (30 mg per 2.2 pounds body weight) has not improved performance of short-term, high-intensity exercise such as weightlifting or sprint cycling by trained athletes,6 7 and no studies on endurance performance or muscle growth have been conducted. Although the effects of glutamine supplementation on immune function after exercise have been inconsistent,8 9 double-blind trials giving athletes glutamine (5 grams after intense, prolonged exercise, then again two hours later) reported 81% having no subsequent infection compared with 49% in the placebo group.10
Are there any side effects or interactions?
No significant side effects have been reported in glutamine studies.
Are there any drug interactions?
Certain medicines may interact with glutamine. Refer to drug interactions for a list of those medicines.
*Athletes and fitness advocates may claim benefits for glutamine based on their personal or professional experience. These are individual opinions and testimonials that may or may not be supported by controlled clinical studies or published scientific articles on glutamine. For more complete and detailed information, including references and safety information, see Glutamine as a nutritional supplement.
References
1. Antonio J, Street C. Glutamine: a potentially useful supplement for athletes. Can J Appl Physiol 1999;24:1–14 [review].
2. Rowbottom DG, Keast D, Morton AR. The emerging role of glutamine as an indicator of exercise stress and overtraining. Sports Med 1996;21:80–97 [review].
3. Welbourne TC. Increased plasma bicarbonate and growth hormone after an oral glutamine load. Am J Clin Nutr 1995;61:1058–61.
4. Macintyre JG. Growth hormone and athletes. Sports Med 1987;4:129–42 [review].
5. Varnier M, Leese GP, Thompson J, et al. Stimulatory effect of glutamine on glycogen accumulation in human skeletal muscle. Am J Physiol 1995;269:E309–15.
6. Antonio J, Sanders MS, Kalman D, et al. The effects of high-dose glutamine ingestion on weightlifting performance. J Strength Cond Res 2002;16:157–60.
7. Haub MD, Potteiger JA, Nau KL, et al. Acute L-glutamine ingestion does not improve maximal effort exercise. J Sports Med Phys Fitness 1998;38:240–4.
8. Rohde T, MacLean DA, Pedersen BK. Effect of glutamine supplementation on changes in the immune system induced by repeated exercise. Med Sci Sports Exerc 1998;30:856–62.
9. Castell LM, Newsholme EA. Glutamine and the effects of exhaustive exercise upon the immune response. Can J Physiol Pharmacol 1998;76:524–32 [review].
10. Castell LM, Poortmans JR, Newsholme EA. Does glutamine have a role in reducing infections in athletes? Eur J Appl Physiol 1996;73:488–90.
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2006-09-07
