Viral Upper Respiratory Infections (Colds and Influenza) and Glutamine

L-glutamine, also known as glutamine, is an amino acid derived from another amino acid, glutamic acid. It is known to help prevent post-exercise infections, such as the "post-marathon sniffle," a cold that develops after endurance exercise. (Vitamin C and echinacea have also shown promise for the prevention of post-exercise infections.)

Glutamine plays a role in the health of the immune system, as well as other bodily functions. Heavy exercise and other stressors can deplete the body's glutamine reserves, particularly in muscle cells. This is probably why supplementing with glutamine is useful for preventing exercise-induced infections.

Read more details about Glutamine.

There is some evidence that the supplement glutamine may, like vitamin C, help prevent post-exercise infections.^78-83 For example, a double-blind, placebo-controlled study evaluated the benefits of supplemental glutamine (5 g) taken at the end of exercise in 151 endurance athletes.⁸⁴ The result showed a significant decrease in infections among treated athletes. Only 19% of the athletes taking glutamine got sick, as compared to 51% of those on placebo. Echinacea has also shown a bit of promise for this purpose.¹⁶⁰

Typical therapeutic dosages of glutamine used in studies range from 3 to 30 g daily, divided into several separate doses. There is strong evidence that glutamine is safe at levels up to 14 g per day, and probably higher.¹

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Safety Issues

As a naturally occurring amino acid, glutamine is thought to be a safe supplement when taken at recommended dosages. There is strong evidence that glutamine is safe at levels up to 14 g per day, although higher dosages have been tested without apparent adverse effects. ¹ Nevertheless, those who are hypersensitive to monosodium glutamate (MSG) should use glutamine with caution, as the body metabolizes glutamine into glutamate. Also, because many anti-epilepsy drugs work by blocking glutamate stimulation in the brain, high dosages of glutamine might conceivably overwhelm these drugs and pose a risk to people with epilepsy . Finally, in one case report, high doses of the supplement L-glutamine (more than 2 g per day) may have triggered episodes of mania in two people not previously known to have bipolar disorder . ² Maximum safe dosages for young children, pregnant or nursing women, or those with severe liver or kidney disease have not been determined.

Interactions You Should Know About

If you are taking:

• Antiseizure medications, including carbamazepine , phenobarbital , phenytoin (Dilantin) , primidone (Mysoline) , and valproic acid (Depakene) : Use glutamine only under medical supervision.
• Nelfinavir or other protease inhibitors for HIV, or cancer chemotherapy drugs: Use of glutamine may reduce intestinal side effects.

1. Shao A, Hathcock JN. Risk assessment for the amino acids taurine, L-glutamine and L-arginine. Regul Toxicol Pharmacol. 50(3):376-99.
2. Mebane AH. L-Glutamine and mania [letter]. Am J Psychiatry. 1984;141:1302-1303.

1. Shao A, Hathcock JN. Risk assessment for the amino acids taurine, L-glutamine and L-arginine. Regul Toxicol Pharmacol. 50(3):376-99.
78. Castell LM, Poortmans JR, Newsholme EA. Does glutamine have a role in reducing infections in athletes? Eur J Appl Physiol Occup Physiol. 1996;73:488-490.
79. Castell LM, Newsholme EA. Glutamine and the effects of exhaustive exercise upon the immune response. Can J Physiol Pharmacol. 1998;76:524-532.
80. Rohde T, MacLean DA, Hartkopp A, et al. The immune system and serum glutamine during a triathlon. Eur J Appl Physiol. 1996;74:428-434.
81. 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.
82. Castell LM, Newsholme EA. The effects of oral glutamine supplementation on athletes after prolonged, exhaustive exercise. Nutrition. 1997;13:738-742.
83. Mackinnon LT, Hooper SL. Plasma glutamine and upper respiratory tract infection during intensified training in swimmers. Med Sci Sports Exerc. 1996;28:285-290.
84. Castell LM, Poortmans JR, Newsholme EA. Does glutamine have a role in reducing infections in athletes? Eur J Appl Physiol Occup Physiol. 1996;73:488-490.
160. Hall H, Fahlman MM, Engels HJ. Echinacea Purpurea and Mucosal Immunity. Int J Sports Med. 2007 Apr 13. [Epub ahead of print]