Muscle mass and gastrointestinal tract support * l-Glutamine is the most abundant amino acid in the body. In times of metabolic stress, glutamine is utilized by the body for tissue repair, gastrointestinal tract support, and natural defense system function. Glutamine plays a large role in maintaining healthy intestinal integrity by enhancing the intestine's protective mucosal lining. In addition, glutamine is important in the preservation of muscle mass. l-Glutamine nutritionally supports the mucosal lining and the healthy functioning of the gastrointestinal tract, as well as lean muscle mass.