L-Glutamine Supplements and Athletic Performance

Learn About Slowing Muscle Breakdown and Improving Immune Function

Sports Supplement L-Glutamine

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Glutamine, or L-glutamine, is a naturally occurring non-essential amino acid that is commonly stored in muscles and released into the bloodstream during times of physical stress. Athletes who take glutamine supplements generally do so in order to prevent muscle breakdown and to improve immune system functioning. While that may have some benefit in select individuals, it may be unnecessary for others.

L-Glutamine and Your Body

L-glutamine is used by the immune system during times of stress, including prolonged and intense physical exertion, such as during long-distance endurance exercise (marathons, triathlons, ultra-distance events) and high-intensity strength training workouts. 

Increasing data shows that transient inflammation, oxidative stress, and interruptions in immune system functioning in endurance athletes may be linked to deficiencies in L-glutamine and other nutrients such as polyphenols.

For this reason, marathon runners who are at risk of catching colds, cases of flu, or other illnesses for several days after a competition may be recommended L-glutamine supplements as part of a clinical nutrition protocol for immune suppressed individuals.

It is important to eat a healthy, varied diet to supply your body with all the amino acids it needs, including L-glutamine.

Natural Sources of L-Glutamine

Most people meet the nutritional need for glutamine through their diet.

L-glutamine is abundant in high-protein foods and select plant sources, including:

  • Beef
  • Chicken
  • Pork
  • Fish
  • Eggs
  • Dairy (milk, yogurt, cheese)
  • Cabbage
  • Beets
  • Beans
  • Spinach
  • Peanuts
  • Barley

Note: Cooking can destroy glutamine in certain foods, especially vegetables.

L-Glutamine Supplements for Athletes

It's hard to determine from the scientific literature, the benefit of glutamine supplementation in otherwise healthy individuals who get adequate nutrition from their diet. However, if you train hard and your diet is lacking proper nutrients, there is some research indicating L-glutamine supplements may be worth considering, including:

  • A study finding oral glutamine may decrease the incidence of illness and infection in athletes involved in extreme training regimens.
  • A study finding glutamine supplements can help maintain muscle mass by preventing protein breakdown and improving glycogen synthesis, thereby increasing muscle glycogen stores.

L-glutamine is not banned by any sports organizations and is classified as a nutritional supplement. It can be found in most health food stores in the form of gels or tablets and is often an ingredient in many commercial protein powders.

A Word From Verywell

If you are an endurance athlete, you may be at risk of illness after extreme training and competitions, especially if you do not maintain proper nutrition. Before using an L-glutamine supplement, consult with a sports nutritionist to evaluate your diet. If you experience prolonged issues with immunosuppression, make an appointment with a doctor to rule out more serious health problems.

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Article Sources

Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  • Bowtell JL, Gelly K, Jackman ML, Patel A, Simeoni M, Rennie MJ (1999). Effect of oral glutamine on whole body carbohydrate storage during recovery from exhaustive exercise. Journal of Applied Physiology 86:1770-1777. doi:10.1152/jappl.1999.86.6.1770

  • Castell LM, Poortmans JR and Newsholme EA (1996). Does glutamine have a role in reducing infections in athletes? European Journal of Applied Physiology 73: 488-490. doi:10.1007/BF00334429

  • Nieman, D., & Mitmesser, S. (2017). Potential Impact of Nutrition on Immune System Recovery from Heavy Exertion: A Metabolomics Perspective. Nutrients, 9(5), 513. doi:10.3390/nu9050513 

  • Rowbottom DG1, Keast D. Mortan AR (1996). The emerging role of glutamine as an indicator of exercise stress and overtraining. Sports Med. Feb. 21(2):80-97. doi:10.2165/00007256-199621020-00002