L-Glutamine Supplements and Athletic Performance

Learn About Slowing Muscle Breakdown and Improving Immune Function

Sports Supplement L-Glutamine

The sports supplement industry is full of products that claim to give athletes and edge, boost performance and speed up recovery. Because the supplement industry is not highly regulated, it's hard to know what claims are true, and what products will simply drain your wallet.


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 stress.

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

When there is a deficiency of glutamine or when the amount of glutamine is drastically reduced during increased stress, the body experiences a suppression of the immune system until glutamine levels are restored through either diet or supplements.

For this reason, marathon runners are often at risk of catching colds, cases of flu, and other illness for several days after a competition. Intense endurance exercise not only depletes glutamine stores but has been linked to a temporary decrease in immune system function and a susceptibility to upper respiratory infections and other illness.

Natural Sources of L-Glutamine

L-Glutamine is most abundant in high-protein foods, such as meat, fish, legumes, and dairy. Two particularly high vegetable sources are uncooked cabbage and beets. Cooking can destroy glutamine, especially in vegetables. General food sources of glutamine include:

  • Animal sources: such as beef, chicken, pork, fish, eggs, milk, yogurt, and cheese
  • Uncooked plant sources including beans, spinach, peanuts, barley, cabbage, and beets.

L-Glutamine Supplements for Athletes

Athletes who take glutamine supplements generally do so in order to prevent muscle breakdown and to improve immune system functioning. Several clinical studies have found that oral glutamine may decrease the incidence of illness and infection in endurance athletes or athletes involved extreme training regimens. Research has also found that glutamine supplements can help maintain muscle mass by preventing protein breakdown and improving glycogen synthesis thereby increasing muscle glycogen stores.

L-Glutamine is a classified as a nutritional supplement and is not banned by any sports organizations. 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. Due to the limited research, there are no established guidelines for doses, but our Bodybuilding Expert recommends starting at 3 to 5 grams per day.

While the current research of glutamine on immune system function and muscle building is encouraging, it’s still hard to determine the benefit of supplements in otherwise healthy individuals who get adequate nutrients in their diet.

Bottom Line

Most athletes probably don't need to take L-Glutamine supplements. If you eat a healthy, varied diet, and you exercise at a moderate level, it's likely that your body will supply all the right amino acids to keep you going and keep you healthy. If you train hard and your diet is lacking proper nutrition, perhaps the supplements can provide a benefit.

The evidence linking Glutamine supplementation with performance or strength enhancement is very, very slim. However, if you are an endurance athlete, or train to exhaustion day after day (such as in multi-day competitions or ultra-distance events), there is evidence that L-Glutamine supplementation may aid endurance and most importantly, it may reduce your risk of illness, and improve recovery after extreme training and competition.

If you are considering using an L-Glutamine supplement, it's smart to consult with a sports nutrition expert first, to evaluate your diet. And then, if you use them, seek out a reputable source. 

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Article Sources
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