L-glutamine is the most abundant nonessential amino acid in the human body and is one of the few that can directly pass through the blood-brain barrier. It could be found in the bloodstream and in the skeletal muscles. That amino acid is the best source of rapid muscle growth for athletes and body builders.
There is scientific evidence that when taken as a drink, it could increase the levels of HGH by stimulating the pituitary gland. This is one of the most important amino acids for the human body, as the muscles recognize it as a source of energy and it gets absorbed by the cells. That ensures 100% muscle growth and lean muscle mass gain. L-glutamine is known as the king of sports supplements and is present in the daily diet of every self-respecting athlete.