(Doctor's Best) L-Tryptophan is a vital link for the production of the brain neurotransmitter serotonin. Serotonin is a key to your mood, hunger, and sleep health. This essential amino acid is a pharmaceutical grade amino. It is not made by the body and must be obtained through diet or supplementation. Suggested use is 1 or 2 capsules daily, or as directed by a health practitioner.