Glutamine is a conditionally essential amino acid, meaning the body can synthesize + produce it, but under certain circumstances will require exogenous supplementation.
Glutamine has been researched since the 1800s, and plays multiple critical roles in the body.
It has been shown to: speed recovery and reduce muscle soreness after exercise, reduce intestinal permeability, play a role in production of neurotransmitters, liver function, anti-oxidant function…etc.
More on these roles another time…
Glutamine serves as the main fuel for cells of the immune system. But, the glutamine synthesis+supply in the body is not enough to meet the demands during catabolic conditions such as: during intense & exhaustive physical exercise; surgeries; traumas; cancer; sepsis; infections.
Approximately 80% of the body’s glutamine is found in skeletal muscle, and glutamine makes up approx. 50% of the total amino acid pool in the body. When the demand for glutamine increases , such as during illness to fuel the immune system; among many other changes, skeletal muscle gets broken down to supply the glutamine for immune cell fuel.
This is great for fighting that cold, but not so much for our poor muscles, especially in athletes who cannot afford this set-back.
Athletes under intense, exhaustive training are more susceptible to the adverse effects from high-intensity exercise. One of the adverse effects is an impaired immune system function. Conditions of stress – whether emotional or physical – elevate cortisol levels. Chronic elevations of cortisol can lead to impaired immune system function.
Thus, athletes under intense training regimens may be more susceptible to infection.
In fact, prolonged exhaustive exercise ,*without adequate recovery on all levels*, has been shown to increase the incidence of getting the common cold.
In summary; not only is glutamine important to aid in muscle recovery from intense exercise, it is also critical to provide fuel to the immune system , especially for athletes who may be more susceptible to getting sick, and finally, to help mitigate the effects of muscle breakdown during illness.
Sources: Legault Z et al 2014, Cruzat V.F et al 2014, Cruzat V.F et al 2018.