L-Glutamine Supplements and Athletic Performance

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

The immune system uses L-glutamine 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. But in general, the body stores enough glutamine to overcome deficiencies created by endurance exercise.

Other nutrients should be adequate in order to improve overall immunity: Vitamins A, C, D, E, and zinc. 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

From the scientific literature, it's hard to determine 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.

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. Since the FDA does not regulate supplements, be sure to look for third-party labels (like USP or NSF) to ascertain the safety of the product and the ingredients listed on the label.

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 or sports doctor to evaluate your diet. If you experience prolonged issues with immunosuppression, make an appointment with a doctor to rule out more serious health problems.