L-Tryptophan
Amino Acid ·Exploratory record · not publication-reviewed ·Updated July 13, 2026
Essential amino acid precursor to serotonin and melatonin.
Exploratory record, not a reviewed medical publication.
See the editorial and medical-review policies for the publication gate.
This generated database record has not completed a claim-level review by a qualified human medical reviewer. Bibliography links and evidence labels are not approval. The page remains available for reference and is excluded from search indexing.
What the research says.
A quick, data-only summary. The full evidence, dosing, and sources are below.
L-Tryptophan is an amino acid most often used for sleep support, mood enhancement, serotonin production. NutriStack rates the overall evidence as moderate. A typical adult dose is 500-1,000 mg before bed, commonly taken as free-form l-tryptophan. This profile indexes 17 sources.
The bottom line
Evidence rating moderate. Most-documented uses: sleep support, mood enhancement, serotonin production. 17 sources indexed (1987–2025), with 0 interaction records on file.
How it works, mechanistically.
Core mechanism
Converted to 5-HTP by tryptophan hydroxylase, then to serotonin by AADC. Serotonin is further converted to melatonin by AANAT and ASMT in the pineal gland.14,15
Dosing & protocol.
Take on empty stomach away from protein (competition for transport)3,5
What it actually costs.
Real-world pricing across three quality tiers. Assumes Free-Form L-Tryptophan.
Assumes 500-1,000 mg before bed. Vendor basis: NOW/iHerb, Vitacost, Life Extension, and Amazon marketplace; higher-dose capsules raise daily cost. Updated 2026-05-28.
The same dose, as food.
How much you'd eat to match a supplemental dose.
Foods provide tryptophan within protein and may not have the same timing effects as isolated bedtime dosing.
Full safety detail.
Sources, by evidence tier.
Numbered references. Citations throughout the page link here.
Meta-analyses & systematic reviews
7- 1The Tryptophan-Kynurenine pathway in people living with HIV: a systematic reviewPMIDSebigi TW, Asia LK, January GG et al. · Infection · 2025
Sebigi TW, Asia LK, January GG et al.. The Tryptophan-Kynurenine pathway in people living with HIV: a systematic review. Infection. 2025
- 2Effect of Tryptophan Restriction in the Therapy of Irritable Bowel Syndrome: a Systematic ReviewPMIDWang B, Cheng P, Jin B et al. · International journal of general medicine · 2024
Wang B, Cheng P, Jin B et al.. Effect of Tryptophan Restriction in the Therapy of Irritable Bowel Syndrome: a Systematic Review. International journal of general medicine. 2024
- 3The impact of tryptophan supplementation on sleep quality: a systematic review, meta-analysis, and meta-regressionPMIDSutanto CN et al. · Nutrition Reviews · 2022
Tryptophan supplementation can shorten wake after sleep onset and improve subjective sleep quality.
- 4Changes in Tryptophan-Kynurenine Metabolism in Patients with Depression Undergoing ECT-A Systematic ReviewPMIDAarsland TIM, Instanes JT, Posserud MR et al. · Pharmaceuticals (Basel, Switzerland) · 2022
Aarsland TIM, Instanes JT, Posserud MR et al.. Changes in Tryptophan-Kynurenine Metabolism in Patients with Depression Undergoing ECT-A Systematic Review. Pharmaceuticals (Basel, Switzerland). 2022
- 5Effects of tryptophan supplementation on sleep quality: a systematic review and meta-analysisSource linkedPMIDSutanto CN, Loh WW, Kim JE · Nutr Rev · 2022
- 6Estimation of the tryptophan requirement in piglets by meta-analysisPMIDSimongiovanni A, Corrent E, Le Floc'h N et al. · Animal : an international journal of animal bioscience · 2012
Simongiovanni A, Corrent E, Le Floc'h N et al.. Estimation of the tryptophan requirement in piglets by meta-analysis. Animal : an international journal of animal bioscience. 2012
- 7Tryptophan and 5-hydroxytryptophan for depression: a meta-analysisSource linkedPMIDShaw K, Turner J, Del Mar C · Cochrane Database Syst Rev · 2002
Randomized controlled trials
2- 8Effects of Coenzyme Q10, Tryptophan, and Magnesium Supplementation on Fatigue in Patients with Fibromyalgia - A Randomized TrialPMIDRosselló Aubach L, Fornós Roca X, Fernández Álvarez ME · Journal of dietary supplements · 2025
Rosselló Aubach L, Fornós Roca X, Fernández Álvarez ME. Effects of Coenzyme Q10, Tryptophan, and Magnesium Supplementation on Fatigue in Patients with Fibromyalgia - A Randomized Trial. Journal of dietary supplements. 2025
- 9Oral tryptophan activates duodenal aryl hydrocarbon receptor in healthy subjects: a crossover randomized controlled trialPMIDRueda GH, Causada-Calo N, Borojevic R et al. · American journal of physiology. Gastrointestinal and liver physiology · 2024
Rueda GH, Causada-Calo N, Borojevic R et al.. Oral tryptophan activates duodenal aryl hydrocarbon receptor in healthy subjects: a crossover randomized controlled trial. American journal of physiology. Gastrointestinal and liver physiology. 2024
Reviews & position papers
7- 10Toxicology and safety study of L-tryptophan and its impurities for use in broiler feedPMIDKo SM, Park JE, Lee JY et al. · Journal of applied toxicology : JAT · 2024
Ko SM, Park JE, Lee JY et al.. Toxicology and safety study of L-tryptophan and its impurities for use in broiler feed. Journal of applied toxicology : JAT. 2024
- 11Toxicology and safety study of L-tryptophan and its impurities for use in swinePMIDPark JE, Ko SM, Han HJ et al. · Journal of applied toxicology : JAT · 2024
Park JE, Ko SM, Han HJ et al.. Toxicology and safety study of L-tryptophan and its impurities for use in swine. Journal of applied toxicology : JAT. 2024
- 12Tryptophan Metabolism Disorder-Triggered Diseases, Mechanisms, and Therapeutic Strategies: A Scientometric ReviewPMIDChen X, Xu D, Yu J et al. · Nutrients · 2024
Chen X, Xu D, Yu J et al.. Tryptophan Metabolism Disorder-Triggered Diseases, Mechanisms, and Therapeutic Strategies: A Scientometric Review. Nutrients. 2024
- 13A systematic review of the effect of L-tryptophan supplementation on mood and emotional functioningPMIDKikuchi AM et al. · Journal of Dietary Supplements · 2021
L-tryptophan intake (0.14-3 g/day) may be effective to decrease anxiety and increase positive mood in healthy individuals.
- 14L-tryptophan administration and increase in cerebral serotonin levels: Systematic reviewPMIDFernstrom JD et al. · BMC Psychiatry · 2018
L-tryptophan is readily converted to serotonin in the brain and can modulate sleep, mood, and cognitive function via serotonergic pathways.
- 15Effects and side effects associated with the non-nutritional use of tryptophan by humansPMIDFernstrom JD · Journal of Nutrition · 2012
Side effects at higher doses (70-200 mg/kg) include tremor, nausea, dizziness; serotonin syndrome risk when combined with serotonergic drugs; historical EMS outbreak linked to contaminant, not tryptophan itself.
- 16Evaluation of L-tryptophan for treatment of insomnia: a reviewPMIDHartmann E et al. · Journal of Clinical Psychiatry · 1987
L-tryptophan in doses of 1 g or more produces an increase in subjective sleepiness and a decrease in sleep latency, with best results in mild insomnia.
Common questions.
Quick answers about L-Tryptophan, drawn from the data on this page.
What is L-Tryptophan?
Essential amino acid precursor to serotonin and melatonin.
What is L-Tryptophan used for?
Commonly cited benefits of L-Tryptophan include: Sleep support; Mood enhancement; Serotonin production. NutriStack rates the overall evidence as moderate.
What is a typical dose of L-Tryptophan?
A typical adult dose of L-Tryptophan is 500-1,000 mg before bed. The commonly recommended form is Free-form L-Tryptophan. These are general ranges, not personalized advice; confirm the right dose with a clinician.
What are the side effects of L-Tryptophan?
Reported side effects include drowsiness, nausea, dry mouth. This is educational information; check with a healthcare professional before use.
How strong is the evidence for L-Tryptophan?
NutriStack rates this as Moderate, meaning several aligned RCTs or one large RCT plus supporting reviews. Full tier criteria are at https://nutristackapp.com/methodology/evidence-tiers.
Use this with your stack
L-Tryptophan in NutriStack.
Add it to your stack, see how it interacts with everything else you take, and get a Stack Score that updates the moment it does.