5-HTP (L-5-Hydroxytryptophan) is an intermediate in the natural conversion of the essential amino acid, tryptophan, to serotonin. Clinical studies have shown that 5-HTP increases the amount and availability of serotonin produced by the body. Increased brain availability of serotonin produced by the body. Increased brain serotonin produced by the body. Increased brain serotonin levels may produce positive effects on emotional well-being, appetite regulation, melatonin production and maintaining a healthy sleep cycle. Source Naturals 5-HTP is naturally derived from the seeds of the African plant Griffonia simplicifolia.