Glutamine is the most abundant amino acid found in human muscle and is commonly found in supplements or as a micronized, instantly soluble powder because supplement manufacturers claim the body's natural glutamine stores are depleted during anaerobic exercise. Serum glutamine is used by the body to counteract the acidosis that results from exercise; in order to replenish the loss of glutamine from the bloodstream, the body catabolizes glutamine from the muscle. Ingestion of supplemental glutamine may therefore help ensure a ready supply for the muscles. It is also argued that a deficiency may lead to a weakened immune system and wasting of muscle tissue.

Some studies have shown there to be no significant effect of glutamine on bench press strength, knee-extension torque or lean muscle mass when compared to controls taking a placebo, though another study found that glutamine is beneficial in raising T-helper/suppressor cell ratio in long-distance runners.