5-HTP
Summary
5-HTP is the step between tryptophan and serotonin. A Cochrane review found only two adequate trials (64 people) and called the depression evidence inconclusive; a 2020 review judged most studies weak. Because it raises serotonin, combining it with antidepressants raises concern, and a contaminant called peak X was found in some products.
Key facts
- The immediate precursor of serotonin, made from tryptophan in the body[3]
- Two adequate trials (64 people) in a Cochrane review; better than placebo but inconclusive[1]
- A 2020 review rated current studies relatively weak, with few placebo groups[2]
- Peak X, a contaminant linked to the 1989 tryptophan illness, was reported in some 5-HTP products[3]
- 1 graded human outcome on this page
- October 11, 2026
How it works
Established5-HTP crosses into the brain and is converted to serotonin by aromatic L-amino acid decarboxylase, bypassing the rate-limiting tryptophan hydroxylase step.[3]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Depressive symptoms | Improved | Grade D | Systematic review · n = 64 · 2001 People with unipolar depression or dysthymia in 2 trials Form: 5-HTP or tryptophan · Dose: Varied across trials · Duration: Varied across trials 5-HTP and tryptophan were better than placebo (Peto OR 4.10), but only 2 of 108 trials met quality criteria, so evidence was inconclusive. | 11687048 (opens PubMed)Source [1] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Griffonia simplicifolia seed extract (standardised 5-HTP) | Varies | No head-to-head human absorption data between products in the sources cited here. | Safety review: no definitive cases of eosinophilia-myalgia linked to 5-HTP, but peak X was found in some products.[3] | Depression trials |
Studied doses
Doses studied in human trials ranged from regimen to regimen across the small depression trials; the reviews cited here report no common dose, and retail capsules usually supply 50–100 mg.[1][2]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- Antidepressants and other serotonergic drugsReviewAdding a serotonin precursor to drugs that raise serotonin is a recognised concern for serotonin excess; safety reviews advise caution.[3]
Other supplements
- L-tryptophan, St John’s wortReviewBoth also raise serotonin; combined use stacks the effect.[3]
Who should be careful
- People on antidepressants
- Combining 5-HTP with serotonergic medicines raises concern for serotonin excess.[3]
- Pregnancy and breastfeeding
- No adequate safety data in the sources cited here.[3]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Where to buy 5-HTP
Products from brands we partner with that contain 5-HTP. Listing a product is not a claim that it works; check the amount per serving against the doses studied above, and the label for other ingredients.
- SupersmartPaid link5-HTP2 capsules: 100 mg 5-HTP from Griffonia simplicifolia seed extract (50 mg per capsule); 45 servingsShop at Supersmart (opens in new tab)Price and label checked 2026-10-11 on the brand’s site.
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Frequently asked questions
Does 5-HTP work for depression?
Two small adequate trials suggested benefit, but Cochrane called the evidence inconclusive and later reviews rated studies weak.[1][2]
Can 5-HTP be combined with an SSRI?
Both raise serotonin, and safety reviews flag the combination; that decision belongs with the prescriber.[3]
What is peak X?
A contaminant linked to the 1989 tryptophan illness outbreak; it was reported in some 5-HTP products.[3]
5-HTP or tryptophan?
5-HTP skips the rate-limiting step in serotonin production; tryptophan is also used for protein and niacin. Their trial evidence was pooled together.[1]
Sources
- [1]Tryptophan and 5-hydroxytryptophan for depression.. Cochrane Database Syst Rev, 2001. systematic-review
- [2]Effects of 5-hydroxytryptophan on distinct types of depression: a systematic review and meta-analysis.. Nutr Rev, 2020. meta-analysis
- [3]Safety of 5-hydroxy-L-tryptophan.. Toxicol Lett, 2004. review
What changed
- Removed a 50–300 mg range that came from product labels rather than trials.
- First draft. Every PMID checked against NCBI E-utilities (title, journal and year taken from the PubMed record) and each evidence row written from its PubMed abstract.