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L-Tryptophan
Sole dietary precursor to serotonin and melatonin — supports mood regulation and natural sleep onset more gradually than 5-HTP.
What the evidence says
Tryptophan appears to help in 5 of 6 studies with measurable effects — the evidence leans clearly favourable.
Most evidence is from high-quality meta-analyses and randomised trials published 1982–2026 with a typical study size of 70 participants.
Based on 43 studies · 10 meta-analyses · 11 RCTs · 53,127 total participants
Confidence
HighWhat the studies found
By outcome
Tryptophan has an evidence score of 8/10 — strong evidence based on 43 indexed studies, including 18 meta-analyses. Sole dietary precursor to serotonin and melatonin — supports mood regulation and natural sleep onset more gradually than 5-HTP.
The commonly studied dose of Tryptophan is 500-1000mg before bed. Research points to an estimated optimal dose around 1500mg, with a minimum effective dose near 500mg. Individual response varies — start low and adjust.
The best time to take Tryptophan is before bed. It can be taken on an empty stomach. L-Tryptophan is the rarest essential amino acid and the sole precursor to serotonin and melatonin.
Last reviewed May 2026 · evidence from 39 studies · how we score
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.
L-Tryptophan is an essential amino acid that the body cannot produce, requiring dietary intake. It's the sole precursor to serotonin (the 'feel-good' neurotransmitter) and subsequently melatonin (the sleep hormone). Unlike 5-HTP, tryptophan is one step earlier in the synthesis pathway, offering a more gradual approach to supporting mood and sleep.
Converts to serotonin, supporting mood and well-being
Serotonin is further converted to melatonin for sleep
Can also be converted to niacin (vitamin B3)
How Tryptophan 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.
Tap node to isolate • Pinch to zoom • Tap edge for research
500-1000mg before bed
Loading: Not applicable; start with lower dose and adjust
Can be taken without food
| Form | Type |
|---|---|
| 💊L-Tryptophan capsules | Recommended |
| 🧪Powder | Alternative |
| 💊Tablets | Alternative |
Use pharmaceutical-grade L-Tryptophan from reputable sources to ensure purity.
Minimum: 2 weeks
Optimal: 8 weeks
Cycling: Not required
Note: Taking with carbohydrates may enhance brain uptake by reducing competition from other amino acids. Avoid taking with high-protein foods.
Based on meta-analyses showing tryptophan's role in depression and serotonin pathways. Evidence comes from studies of tryptophan depletion and kynurenine pathway research rather than direct supplementation RCTs. Conservative effectiveness due to indirect evidence.
Fall asleep more quickly
Better overall sense of well-being
Calming effect through serotonin pathway
May cause sleepiness if taken during the day
Consult healthcare provider; limited data
Start with lower doses; may be more sensitive to sedation
Risk of serotonin syndrome - do not combine
May enhance sedative effects
Increased serotonin syndrome risk
High risk of serotonin syndrome
Tip: Take only before bed; reduce dose if excessive
Tip: Take with a small amount of food
Tryptophan is generally safe at recommended doses, with a few precautions worth noting. The most commonly reported side effects are drowsiness, nausea. Use caution if any of these apply to you: Taking SSRIs, SNRIs, or MAOIs (serotonin syndrome risk); Eosinophilia-myalgia syndrome history.
L-Theanine
Likely helpsTea-derived amino acid that boosts alpha brain waves for calm, focused alertness — synergizes with caffeine to reduce jitteriness.