5-HTP
5-HTP (5-hydroxytryptophan) is a direct precursor to serotonin marketed for mood, appetite, and sleep. A handful of small, mostly older or low-quality trials hint at antidepressant and appetite-suppressing effects, but the overall evidence is weak and inconsistent. Because it raises serotonin, combining it with SSRIs, MAOIs, or other serotonergic drugs risks serotonin syndrome, and long-term safety is not well established.
Too little may be associated with
No deficiency; less serotonin support.
Too much may be associated with
Nausea; serotonin syndrome risk with antidepressants.
Informational only — not medical advice.
Neurotransmitters
Hormones
Amino acids
Related
Where to buy
Popular 5-HTP products on Amazon. Not medical advice — talk to a clinician before starting a supplement.
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Research (7)
- Ruminal 5-hydroxytryptophan increases serum serotonin and peripheral vasodilation in growing beef cattle Matos et al. (2026) Full text ↗ PubMed ↗
- L-DOPA and 5-HTP modulation of air-stepping in newborn rats Boulain et al. (2021) Full text ↗ PubMed ↗
- 5-Hydroxytryptophan (5-HTP): Natural Occurrence, Analysis, Biosynthesis, Biotechnology, Physiology and Toxicology Maffei (2020) Full text ↗ PubMed ↗
- 5-HTP efficacy and contraindications Hinz et al. (2012) Full text ↗ PubMed ↗
- Production and Peripheral Roles of 5-HTP, a Precursor of Serotonin Nakamura et al. (2009) Full text ↗ PubMed ↗
- Serotonin a la carte: supplementation with the serotonin precursor 5-hydroxytryptophan Turner et al. (2006) Full text ↗ PubMed ↗
- Sepiapterin Reductase Deficiency Adam et al. (1993) PubMed ↗
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