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5-Hydroxytryptophan
Direct serotonin precursor that may support mood, sleep, and appetite control, but requires caution with certain medications.
What the evidence says
5-HTP doesn't have enough studies with structured effect-size data yet to pool a verdict. Browse the studies below for individual findings.
Most evidence is from high-quality meta-analyses and randomised trials published 1983–2026 with a typical study size of 30 participants.
Based on 55 studies · 2 meta-analyses · 41 RCTs · 4,023 total participants
Confidence
High confidenceBy outcome
Multiple small RCTs suggest antidepressant, sleep and OCD-augmentation benefits. One 60-completer trial against fluoxetine reported response rates of 73% and 80%, with no test of the difference, no placebo arm and no equivalence test. Trials are small and preliminary and a meta-analysis flagged weak methodology.
59 randomised trials
80% were about 5-HTP in an audit of 50 of them
Every randomised or controlled trial of 5-HTP indexed in PubMed, not a hand-picked subset. Meta-analyses and systematic reviews are deliberately excluded from this count: most of them cover many compounds at once, so counting them would inflate it.
PubMed · as of Sep 2026
7 trials ongoing or recruiting · 30 completed on ClinicalTrials.gov
10 of the completed trials have posted results
Registered trials show research momentum for 5-HTP, not proof of effect — a registration is a plan, and posted results are sponsor-reported, not peer-reviewed. They are never counted toward the evidence rating above.
Browse these trials on ClinicalTrials.govClinicalTrials.gov · as of Oct 2026
5-HTP is the immediate precursor to serotonin, the neurotransmitter associated with mood, sleep, and appetite. Derived from the seeds of Griffonia simplicifolia, it crosses the blood-brain barrier and converts directly to serotonin.
Can be effective for mood support and sleep, but interactions with serotonergic medications are a serious concern.
Directly converts to serotonin in the brain
Serotonin converts to melatonin for sleep
How 5-HTP works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Avoid — may affect fetal development
Do NOT use without medical supervision
Not recommended
Risk of serotonin syndrome — potentially life-threatening
Risk of serotonin syndrome
Additive serotonergic load with 5-HTP (precursor) — risk of serotonin syndrome
Both increase serotonin; dangerous combination
Additive serotonergic effects
May increase 5-HTP effects and side effects
Serotonin syndrome risk
Severe serotonin syndrome
Risk of serotonin syndrome
Tip: Take with food; start with low dose; use ginger
Tip: Take in evening; reduce dose
Tip: Take with meals
Tip: Reduce dose
5-HTP has an evidence score of 5.5/10 — moderate evidence based on 55 indexed studies, including 1 meta-analysis. Direct serotonin precursor that may support mood, sleep, and appetite control, but requires caution with certain medications. Representative study: PMID 31504850.
The commonly studied dose of 5-HTP is 50-100mg for sleep; 150-300mg for mood (a typical label dose. The cited 100-300 mg study tested tolerability in 15 healthy men also given carbidopa, not mood). Individual needs vary — start at the lower end of the range and adjust based on how you respond.
The best time to take 5-HTP is before bed. It can be taken on an empty stomach. 5-HTP is a direct serotonin precursor that crosses the blood-brain barrier.
5-HTP has a safety rating of "moderate". That is a category, not a measure of individual risk, and there are precautions worth knowing. The most commonly reported side effects are nausea and vomiting (dose-related), drowsiness, GI upset. Use caution if any of these apply to you: Currently taking SSRIs, SNRIs, MAOIs, or other serotonergic drugs; Carcinoid syndrome; Scleroderma.
Magnesium
Mixed evidenceSupports 300+ enzymatic reactions — critical for sleep, stress response, muscle function, and cognitive health.
L-Theanine
Too few graded studiesTea-derived amino acid that boosts alpha brain waves for calm, focused alertness — synergizes with caffeine to reduce jitteriness.
Tryptophan
Likely helpsSole dietary precursor to serotonin and melatonin, studied for sleep onset and as an add-on to antidepressants.
GABA
Too few graded studiesInhibitory neurotransmitter that calms neural activity — may work through the gut-brain axis for acute anxiety and sleep support.
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Reviewed by Dr. Baher Al Hakim · Last reviewed May 2026 · evidence from 55 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
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