L-Tryptophan is an essential amino acid and a precursor for the synthesis of serotonin. Tryptophan crosses the blood-brain barrier and is converted to L-5-hydroxytryptophan (5-HTP), which in turn is converted into serotonin. Serotonin is an important neurotransmitter necessary for the regulation of appetite, mood, and melatonin production.^‡

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