5-hydroxytryptophan (5-HTP) is an intermediate in the conversion of the essential amino acid l-tryptophan to serotonin. Serotonin is an important neurotransmitter, associated with the regulation of sleep cycles, mood, and appetite. Supplementing with 5-HTP is an efficient way to support brain serotonin production because it bypasses the rate-limiting step in the synthesis of serotonin, the conversion of l-tryptophan into 5-HTP. Seventy percent of orally administered 5-HTP enters the blood stream and then easily crosses the blood-brain barrier. 5-HTP is produced by extraction from the seeds of Griffonia simplicifolia, a tree found mainly in West Africa.