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August 2003

Glutamine: The Conditionally Essential Amino Acid
By Angela Pirisi

Research has shown that glutamine appears to be involved in the regulation of a number of important metabolic processes in skeletal muscle.19 It is therefore hypothesized that glutamine supplementation can help maintain muscle mass. Under severe stress conditions, when glutamine levels are low, the body may respond by breaking down muscle to obtain glutamine. Therefore, experts believe that if supplemental glutamine is taken during these situations, the unnecessary breakdown of muscle may be prevented.20 In fact, researchers believe that glutamine supplementation may increase protein synthesis in the body.21

Overall, it seems that glutamine supplementation can benefit certain athletes, possibly by boosting the immune system and preventing the breakdown of muscle. This may be especially important during times of excessive stress, such as after prolonged strenuous exercise. However, a great deal of information about the role of glutamine during athletic activity is still unclear and will hopefully be clarified by future research.



According to the Physicians' Desk Reference (PDR) for Nutritional Supplements, glutamine added to TPN (total parenteral nutrition-intraverous feed) can help the recovery of the critically ill, such as trauma and surgical patients. The recommended dosages for glutamine added to TPN in a hospital setting are 12 grams per day for post-surgical patients and approximately 25 grams per day for severe trauma and infections.

While there are no specific recommendations concerning glutamine supplementation for athletes, the PDR states that those who use oral glutamine supplements for sports or fitness purposes usually consume 1.5 to 4.5 grams per day in the form of L-glutamine.

Proponents of glutamine supplementation have also indicated its consumption for other purposes. For example, in his book Dr. Atkins' Vita-Nutrient Solution, the late Dr. Atkins recommended between 5 and 20 grams per day to "stimulate the immune system" when needed, between 2 and 3 grams at the onset of a desire for sweets to help ward off the craving, and up to 40 grams per day for inflammatory bowel disease, leaky gut syndrome, during periods of wound healing or during recovery from a prolonged hospital stay. Dr. Atkins recommended powdered L-glutamine as the easiest and most economical way to obtain this amino acid.7

Although Dr. Atkins stated that none of his patients ever developed side effects from glutamine supplementation, the PDR reports that there have been some cases of constipation and bloating associated with high doses of glutamine in TPN. Furthermore, glutamine is contraindicated in anyone who is hypersensitive to any component of a glutamine supplementation product they plan to take. The PDR also warns that those with kidney or liver problems should be cautious in the use of glutamine supplements and that pregnant or nursing women should avoid glutamine supplementation unless specifically prescribed by their physicians. When taking glutamine supplements, it is probably best to split the recommended dosage into two to four divided servings spread throughout the day.3 As with any vitamin or nutritional supplement, the use of glutamine supplementation should only be done under the supervision of a physician.


Glutamine, the most abundant amino acid in humans, is vital to the proper functioning of our bodies. Research has clearly shown that glutamine is necessary for proper intestinal health and that it plays a major role in fighting infections by acting as a fuel for cells in our immune system. Glutamine supplementation is important for the critically ill and may play a role in helping athletes after prolonged strenuous exercise by decreasing infections and preventing the breakdown of muscle. While the role of glutamine in these and other situations is promising, additional research is needed. The role of glutamine in the body and the potential advantages of glutamine supplementation for both sick and healthy individuals is the focus of on-going intense research efforts throughout the world.


1. Hendler, Sheldon S., Ph.D., M.D., & Rorvik, David, M.S. (Editors). PDR for Nutritional Supplements. New Jersey: Medical Economics Company, 2001:189-91.

2. Reinaldo A., et al. Branched-chain amino acid supplementation and the immune response of long-distance athletes. Nutrition 2002 May;18(5):376-9.

3. Talbott, Shawn M., Ph.D. A Guide to Understanding Dietary Supplements. New York: The Haworth Press, 2003:414-5.

4. Miller A. Therapeutic considerations of l-glutamine: A review of the literature. Altern Med Rev 1999 Aug;4(4):239-48.

5. Vante JP et al. Plasma-amino acid profiles in sepsis and stress. Ann Surg 1989 Jan;209(1):57-62.

6. Krebs H. Glutamine metabolism in the animal body. In: Mora J, Palacios R (Editors). Glutamine: metabolism enzymology and regulation. Academic Press, 1980:319-29.

7. Atkins, Robert C., M.D. Dr. Atkin's Vita-Nutrient Solution. New York: Simon & Schuster, 1998:167-170.

8. Neu J, et al. Glutamine: clinical applications and mechanisms of action. Curr Opin Clin Nutr Metab Care 2002 Jan;5(1):69-75.

9. O'Dwer ST, et al. Maintenance of small bowel mucosa with glutamine-enriched parental nutrition. J Parenter Enteral Nutr 1989 Nov-Dec;13(6):579-85.

10. Ardawi MSM, et al. Glutamine metabolism in lymphocytes of rats. Biochem J 1983 Jun 15;212(3):835-42.

11. Ardawi MSM, et al. Metabolism in lymphocytes and its importance in the immune response. Essays Biochem 1985;21:1-44.

12. Ziegler TR. Glutamine supplementation in bone marrow transplantation. Br J Nutr 2002 Jan;87(suppl 1):S9-15.

13. Andrews FJ, et al. Glutamine: essential for immune nutrition in the critically ill. Br J Nutr 2002 Jan;87 (suppl 1):S3-8.

14. Castell LM. Can glutamine modify the apparent immunodepression observed after prolonged, exhaustive exercise? Nutrition 2002 May;18(5):371-375.

15. Parry-Billings M, et al. A communicational link between skeletal muscle, brain and cells of the immune system. Intern J Sports Med 1990 May;11 (suppl 2):S122-8.

16. Castell LM, et al. Does glutamine have a role in reducing infections in athletes? Eur J Appl Physiol Occup Physiol 1996;73(5):488-90.

17. Nieman D, et al. Exercise and immune function. Recent developments. Sports Med 1999 Feb;27(2):73-80.

18. Rohde T, et al. Effect of glutamine supplementation on changes in the immune system induced by repeated exercise. Med Sci Sports Exerc 1998 Jun;30(6):856-62.

19. Rennie MJ, et al. Amino acid transport during muscle contraction and its relevance to exercise. Adv Exp Med Biol 1998;441:299-305.

20. Antonio J, Ph.D., & Stout J., Ph.D. (Editors). Sports Supplement Encyclopedia Edition 1. Colorado: Nutricia Institute of Sports Science, 2002:132-3.

21. Hankard RG, et al. Effect of glutamine on leucine metabolism in humans. Am J Physiol 1996 Oct ;271 (4 Pt 1): E748-54.