5-Hydroxytryptophan (5-HTP) is an intermediate in the natural synthesis of the essential amino acid tryptophan. Tryptophan is converted into 5-HTP, which in turn is converted into serotonin, an important neurotransmitter that is associated with the regulation of sleep, mood, appetite, aggression, temperature, sexual behavior and pain sensation. Supplementation with 5-HTP is preferable to supplementing with L-tryptophan. 5-HTP is derived naturally from the seeds of the Griffonia plant, where L-tryptophan is produced synthetically or through bacterial fermentation. 5-HTP crosses into the brain more readily than L-tryptophan, as it is able to cross the blood-brain barrier without competing with other amino acids for uptake. Unlike L-tryptophan, 5-HTP cannot be shunted into niacin or protein production.