L-Tryptophan
L-Tryptophan
TL;DR
L-Tryptophan is the amino-acid precursor of serotonin and melatonin. It reliably shortens the time to fall asleep at 1 g+ and is a reasonable, well-studied option for mild insomnia; claims for depression are plausible but weaker than for 5-HTP or standard care.
Ideal For
- People with mild difficulty falling asleep
- Those wanting a non-sedating, non-habit-forming sleep aid
Avoid If
- You take SSRIs/SNRIs/MAOIs or triptans without medical supervision (serotonin syndrome risk)
- You have eosinophilic disorders
- You are pregnant (insufficient safety data)
Frequently Asked Questions
Overview
L-Tryptophan is an essential amino acid and the sole precursor of serotonin (5-HT) and, downstream, melatonin. A meta-analysis of controlled trials found that doses of 1 g or more significantly reduce sleep latency (time to fall asleep), particularly in mild insomnia; effects below 1 g were unreliable. Tryptophan competes with other large neutral amino acids (LNAAs) for transport across the blood-brain barrier, so a carbohydrate-rich snack enhances its brain uptake by triggering insulin-mediated clearance of competing LNAAs. For depression, tryptophan depletion studies prove serotonin has a causal role in mood, and tryptophan augmentation has shown benefit as an add-on to antidepressants in some trials, but monotherapy evidence is modest. The 1989 eosinophilia-myalgia syndrome (EMS) epidemic was traced to a contaminated batch from a single manufacturer (Showa Denko), not tryptophan itself; modern pharmaceutical-grade products have an excellent safety record. High-protein meals blunt its effect because dietary protein supplies competing amino acids.
How It Works
- Converted to 5-HTP then serotonin via tryptophan hydroxylase (rate-limiting)
- Serotonin is the precursor of melatonin, supporting sleep onset
- Brain uptake is competitively limited by other large neutral amino acids
- Carbohydrate co-ingestion raises the tryptophan:LNAA ratio, enhancing brain delivery
Benefits & Outcomes
Serotonin Support
Tryptophan modestly improves mood and sleep, with transport competition limiting its effect.
Faster Sleep Onset
L-Tryptophan at doses of 1 g or more significantly shortens sleep latency (time to fall asleep) in controlled trials, particularly for mild insomnia. Doses below 1 g are unreliable, and taking it with a small carbohydrate snack improves brain uptake.
Health Concerns Addressed
No linked health concerns yet.
Supporting Research11 studies
Primary fibromyalgia syndrome and 5-hydroxy-L-tryptophan: a 90-day open study
Sarzi Puttini P, Caruso I
Clinical variables including tender point count, anxiety, pain intensity, sleep quality and fatigue improved significantly from baseline over 90 days. Roughly half of participants reported good or fair improvement; side effects were mild and did not require withdrawal.
An eosinophilia-myalgia syndrome related disorder associated with exposure to L-5-hydroxytryptophan
Michelson D, Page SW, Casey R +7 more
Family members taking 5-HTP developed an eosinophilia-myalgia-syndrome-related illness; analysis of their product identified contaminant peaks analogous to those implicated in tryptophan-associated EMS.
Tryptophan and vitamin B6 status in relation to melatonin synthesis: a randomized controlled trial
Hudson C, Hudson SP, Hecht T +1 more
Tryptophan supplementation increased overnight melatonin metabolite excretion and improved sleep continuity.
The impact of tryptophan supplementation on sleep quality: a systematic review, meta-analysis, and meta-regression
Sutanto CN, Loh WW, Kim JE
Tryptophan doses above 1 g reduced wake after sleep onset, while lower doses showed no significant sleep effect.
Tryptophan supplementation and serotonin synthesis: a systematic review of human studies
Kikuchi AM, Tanabe A, Iwahori Y
Tryptophan supplementation improved mood and sleep measures consistent with increased central serotonin synthesis
Tryptophan and 5-hydroxytryptophan for depression
Shaw K, Turner J, Del Mar C
Available evidence suggests tryptophan and 5-HTP are better than placebo for depression, but the quality of studies is insufficient to support clinical use.
Effects of tryptophan loading on human cognition, mood, and sleep
Silber BY, Schmitt JAJ
Tryptophan loading reliably increases subjective sleepiness and shortens sleep latency, with inconsistent cognitive effects.
A systematic review of the effect of L-tryptophan supplementation on mood and emotional functioning
Kikuchi AM, Tanabe A, Iwahori Y
Most trials in healthy adults reported reduced depressive and anxious mood with tryptophan, though effects were small.
Post-epidemic eosinophilia-myalgia syndrome associated with L-tryptophan
Allen JA, Peterson A, Sufit R
Cases of eosinophilia-myalgia syndrome continued to be reported in patients taking L-tryptophan after the 1989 epidemic.
Effects of tryptophan-enriched cereals consumed at breakfast and dinner on sleep, mood and melatonin in elderly people
Bravo R, Matito S, Cubero J
Tryptophan-enriched cereals increased sleep efficiency and urinary melatonin while reducing anxiety and depression scores in older adults.
Serotonin a la carte: supplementation with the serotonin precursor 5-hydroxytryptophan
Turner EH, Loftis JM, Blackwell AD
Peripheral serotonin precursor loading raises brain serotonin synthesis, but clinical outcomes depend heavily on baseline status.
Safety Information
Potential Side Effects
Drowsiness, nausea, vivid dreams; dry mouth. Serotonin syndrome possible in combination with serotonergic drugs.
Contraindications
Concurrent MAOI use; history of EMS.
Drug Interactions
- SSRIs/SNRIs/MAOIs/triptans (serotonin syndrome risk)
- Sedatives (additive drowsiness)
Pregnancy & Breastfeeding
Pregnancy: insufficient_data
Breastfeeding: insufficient_data
Dosage Guidelines
Dosage Used in Studies
500-3000 mg
Best Time to Take
30-45 min before bed
Best Form
Pharmaceutical-grade (USP/EP purity) L-tryptophan
Dosing by Goal
| Goal | Dose | Notes |
|---|---|---|
| 1000 mg | Sub-1g doses are unreliable per meta-analysis | |
| 1-3 g/day divided | Best studied as add-on, not monotherapy |
Forms Compared
Standard; take 2 for the effective 1 g threshold
5-HTP skips the rate-limiting step; tryptophan has better long-term safety data
Food & Timing
Away from protein-rich meals; with a small carbohydrate snack to boost brain uptake.
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.