Glutamine, the most abundant amino acid in the body, is a precursor in the synthesis of other amino acids and of glucose for energy. The body can produce glutamine from glutamic acid in the skeletal muscle and liver. Cells of the immune system, the small intestine and the kidney are the major consumers of glutamine.
Intense exercise creates a need for glutamine that may exceed the body’s ability to produce it. If an external source is unavailable, skeletal muscle will be broken down in order to meet the glutamine requirements of the rest of the body.
Studies have shown the efficacy of glutamine supplementation in maintaining muscle mass and immunity in critically ill patients and in those recovering from extensive burns and major surgery. While there is a lack of specific studies conducted in athletes, the use of glutamine supplements to enhance athletic performance has strong theoretical and anecdotal support. For example, it is thought that glutamine stimulates glycogen synthase, an enzyme that controls the synthesis and storage of glycogen fuel in muscles and liver. Glutamine supplements have also been reported to increase levels of growth hormone, a stimulator of protein synthesis that causes gains muscle mass and strength.