5-HTP is a direct precursor to serotonin. Our research shows moderate evidence for depression and appetite suppression, but the SSRI interaction makes this a high-risk supplement for anyone on antidepressants. Only take under medical supervision.
5-HTP (5-hydroxytryptophan) is an amino acid naturally produced in the body from L-tryptophan. It serves as the immediate precursor to serotonin — your body converts 5-HTP to serotonin via aromatic L-amino acid decarboxylase. Unlike tryptophan, 5-HTP crosses the blood-brain barrier readily and doesn't compete with other amino acids for transport, making it a more direct route to increase central serotonin levels.
Additive serotonergic effects → serotonin syndrome risk
Same serotonin syndrome risk
Dramatically increased serotonin levels → serotonin syndrome
Additive serotonergic effects
Increases 5-HTP bioavailability; unclear clinical significance
Serotonergic opioid; additive serotonin risk
Additive serotonergic effects
Additive serotonergic effects
Not Prohibited (2026 WADA list)
Turner EH et al. Serotonin a la carte: supplementation with the serotonin precursor 5-hydroxytryptophan. *Pharmacol Ther.* 2006.
(2006). PMID: 15586095
Birdsall TC. 5-Hydroxytryptophan: a clinically-effective serotonin precursor. *Altern Med Rev.* 1998.
(1998). PMID: 22796340
Shaw K et al. Tryptophan and 5-hydroxytryptophan for depression. *Cochrane Database Syst Rev.* 2002.
(2002). PMID: 20816752
Cangiano C et al. Eating behavior and adherence to dietary prescriptions in obese adult subjects treated with 5-hydroxytryptophan. *Am J Clin Nutr.* 1992.
(1992). PMID: 1384305
Reviewed by the Scan Dose Research Team and Clinical Advisory Board | Last updated: April 2026
Not medical advice. Based on published clinical research and systematic reviews.