About 60% of the total free amino acid content of the body is glutamine. During stress, major changes occur in glutamine levels. The muscle concentration decreases sharply, whereas the immune and gut cells show an increase in demand. The plasma glutamine level may drop below the physiological level, resulting in a situation of imbalance and increased vulnerability to infections. In this condition, the body needs an extra supply of glutamine from the diet. Dr. Eric Newsholme and his associates at Oxford University in the United Kingdom were among the first to hypothesize that an amino acid imbalance may result from strenuous exercise and, as a consequence, induce a number of phenomena that are collectively referred to as the “overtraining syndrome.” Decreased performance, depressed mood and increased incidence of infections are among the many symptoms that are related to the syndrome, which has been experienced by runners, cyclists, swimmers, skiers, ballet dancers, rowers and even race horses.  Dietary glutamine plays a role in counteracting these phenomena because, as has been shown repeatedly, endurance exercise decreases the plasma glutamine level, suggesting that the muscles cannot provide enough of the nutrient.Inadequate amounts of circulating glutamine may lead to impaired immune function and increased susceptibility to infection among athletes suffering from overtraining syndrome. In addition, glutamine consumption by the small intestine has been found to occur at a very high rate. Observations of gastrointestinal disorders, particularly of diarrhea and food allergies, may be due, at least in part, to low concentrations of circulating glutamine. Recently, it was also shown that glycogen storage in the muscles occurred significantly faster when study subjects consumed protein together with carbohydrates as compared to carbohydrates alone. One of the responsible dietary factors for this faster glycogen recovery is thought to be glutamine.  International Sports Sciences Association (ISSA) 8th Edition Text