L-Glutamine

L-glutamine is the most abundant amino acid in the human body, accounting for over 60% of the free amino acid pool in skeletal muscle. During periods of physiological stress — intense training, caloric restriction, illness, or trauma — glutamine demand increases dramatically, and the body's production capacity may not keep pace.

Glutamine serves as the primary fuel source for enterocytes (intestinal lining cells) and immune cells, making it critical for gut barrier integrity and immune function. Athletes with high training loads are at increased risk of upper respiratory tract infections and GI distress — both of which are linked to glutamine depletion.