Supplements 101: What is Glutamine?

What is Glutamine?

Glutamine (aka L-Glutamine) is the most abundant amino acid in the body and makes up 60% of our muscles. It is released into the bloodstream during times of stress and is capable of supporting brain health, digestion, immune function, and muscular energy & recovery.

Glutamine During Times of Stress

Glutamine is used by the immune system during times of stress such as physical trauma, burns, and starvation. It is also used during prolonged and intense exercise, which the body interprets as a stressful event.

A Building Block for Protein Synthesis

L-Glutamine aids in protein synthesis, which is the biological process where amino acids align to create proteins. This process promotes healthy intestines capable of absorbing nutrients, healthy organ function, a high-functioning brain, muscle growth, increased athletic performance, and more.

Glutamine and Gut Health

Glutamine supports the lining of the gastrointestinal tract, which starts at your mouth and ends with your colon. Your intestinal lining actually uses L-Glutamine as fuel to create a strong surface for digestion and absorption to promote gastrointestinal integrity, which means it can help support immune defense, promote a healthy mucosal lining in our intestines, and neutralize free radicals.

Glutamine and Immune Health

Over 70% of the body's immune system lives in the lining of the intestinal tract in the form of immune cell receptors. Because they are inside the gut, glutamine also provides fuel for immune cells. The presence of glutamine in the tissue surrounding these cells allows white blood cells to grow. In the gut, glutamine is needed for cellular production and cell growth, and to assist in the absorption and transport of nutrients. It also maintains nitrogen balance and prevents the burning of other amino acids for energy.

Glutamine and the Brain

L-Glutamine supports the brain by fueling two of the brain’s most important neurotransmitters, glutamic acid and gamma-aminobutyric acid (GABA) to support energy, focus and learning. It also supports mental function by supplying a direct source of energy to the brain.

Glutamine for Recovery After Exercise

For athletes and fitness fanatics, supplementing with Glutamine could potentially provide benefits such as:

  • Helping offset the blood glutamine drops during prolonged, strenuous exercise.
  • Combatting fatigue or poor performance potentially caused by overtraining. It does this by supporting an immune response.
  • Supporting the replenishment of muscle stores, aiding in quicker recovery.
  • Supporting sports-related recovery.
  • Promotes the protection of lean mass + muscle, bone, connective tissue, organs
  • Glutamine helps reduce sugar cravings by binding to the insulin receptors. The timing of taking the glutamine matters. Take the powder either before you know the cravings usually hit or if the cravings are extreme, take 1 tsp 4x/day.

There is evidence too much intense exercise, such as repetitive long-distance running, marathon training, or triathlon training, reduces immunity. Intense exercise also lowers blood levels of Glutamine, which can remain persistently low with overtraining.1 

The recovery period immediately after and for up to one hour after exercise is the critical window when optimal nutrition becomes the most fundamental factor in exercise recovery. Eating enough carbs, protein, and glutamine are all very important for the recovery process. Vitamin C and Vitamin E also support healthy exercise recovery.

Overtraining syndrome is when an athlete is training vigorously, yet performance deteriorates. One sign of overtraining syndrome is a suppressed immune function, with an increased incidence of upper respiratory tract infections. An increase incidence of these infections is also associated with high volume and/or high-intensity training, as well as with excessive exercise, such as marathon or triathlon training. The upper respiratory tract infection normally manifests between 3 to 72 hours post-race.2

The effects of glutamine supplementation on immune function after exercise have been inconsistent,3, 4 but a double-blind trial giving athletes glutamine (5 grams after intense, prolonged exercise, then again two hours later) reported 81% having no subsequent infection compared with 49% in the placebo group.5

Your cells can only be as healthy as the environment they're provided. Consuming adequate amounts of L-Glutamine is a must for feeding your cells what they need, including muscle, bone, connective tissue cells, organ cells.

Kelly Harrington, MS, RDN

Registered Dietitian Nutritionist


1. 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 [review].

2.  Lakier Smith L.  Overtraining, excessive exercise, and altered immunity:  is this a T helper-1 versus T helper-2 lymphocyte response?  Sports Med. 2003;33(5):347-64.

3. Rohde T, MacLean DA, Pedersen BK. Effect of glutamine supplementation on changes in the immune system induced by repeated exercise. Med Sci Sports Exerc 1998;30:856–62.

4. Castell LM, Newsholme EA. Glutamine and the effects of exhaustive exercise upon the immune response. Can J Physiol Pharmacol 1998;76:524–32 [review].

5. Castell LM, Poortmans JR, Newsholme EA. Does glutamine have a role in reducing infections in athletes? Eur J Appl Physiol 1996;73:488–90.

Natural Products Foundation:  Glutamine 

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