Metabolism and glutamine supplementation in sports

Glutamine is considered a conditionally essential amino acid. The body can synthesize glutamine, although conditions of metabolic stress, including strenuous and prolonged or exhaustive exercise can reduce the availability of glutamine. The donation of nitrogen for the formation of nucleic acids, the acid-base balance, the aminogenesis, the supply for energy substrate and synthesis of proteins and intracellular antioxidants are some of the functions and destinations that glutamine is involved. The reduced availability of glutamine can influence a variety of functions, including the amount of injury, the immune and antioxidant systems and inflammation induced by physical exercise. Supplementation with glutamine is a known fact in clinical nutrition. However, as a nutritional supplement for sports is still of considerable interest, since oral glutamine in the free form is partially metabolized by enterocytes. An alternative way to cross the intestinal barrier is the use of glutamine dipeptides, such as L-alanyl-Lglutamine. However, the combination of other amino acids, such as L-alanine, also in the free form, may influence the metabolism and effects of glutamine supplementation. Nevertheless, the amounts and fractioning involving the supplementation of glutamine and the possible mechanisms involved need further investigation.