L-Tryptophan
Also sold as: Tryptophan · Free L-tryptophan
An essential amino acid and precursor to serotonin, melatonin and kynurenine metabolites. Supplemental research suggests less wakefulness after falling asleep, rather than a broad improvement in every sleep measure.
Sleep Anxiety
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Research
- Sleep: A meta-analysis quantified only four studies: less wakefulness after sleep onset, but no significant pooled latency, total sleep time or efficiency effect.
- Anxiety: Some healthy-adult mood trials were positive, but most were not; this does not establish treatment for an anxiety disorder.
REALITY CHECK // Less nighttime wakefulness does not mean every sleep parameter improves. Depression analyses pooled very few adequate trials and sometimes combined 5-HTP with L-tryptophan. Depletion experiments and a simple low-serotonin story cannot establish treatment efficacy, while serotonergic combinations create real safety concerns.
Levels: how we grade evidence. Grey = evidence of no benefit; amber = evidence it makes this goal worse.
Ratings are self-reported by a self-selected group of users: how it felt, not proof that it works.
Check your bottle
Compare what your label says with what was used in trials. This is a trial range, not a personal prescription.
Enter the amount from your label to see the result.
How it was studied
UPPER LIMIT // No established numeric EFSA/NIH UL is supplied. Study doses of 0.14-6 g/day are not a safety limit. Manufacturing purity matters because eosinophilia-myalgia syndrome was associated with contaminated L-tryptophan.
Summary
Sleep evidence is narrow: WASO SMD -1.08 (95% CI -1.89 to -0.28), based on four quantitatively pooled studies. A mood review found significant benefits in only 4 of 11 RCTs. Depression evidence is old and insufficient; do not replace prescribed treatment.
Mechanism
Brain uptake competes with other large neutral amino acids. Tryptophan feeds serotonin/melatonin and kynurenine pathways; depletion experiments test removal, not the clinical efficacy of adding a supplement.
Typical studied dose
Sleep research suggests a signal at at least 1 g/day; healthy-adult mood trials used 0.14-3 g/day. One PMDD trial used 6 g/day from ovulation to menstrual day 3 over three cycles, a specialist clinical protocol rather than a general-use dose.
Upper limit
No established numeric EFSA/NIH UL is supplied. Study doses of 0.14-6 g/day are not a safety limit. Manufacturing purity matters because eosinophilia-myalgia syndrome was associated with contaminated L-tryptophan.
Popular stacks with L-Tryptophan
Not enough stack data yet. A combination with L-Tryptophan appears here once 5 people rate the same set.
Forms and label traps
| Form on label | Active content | Studied range / day | Absorption & GI tolerance | Verdict |
|---|---|---|---|---|
| Free L-tryptophan powder / capsules Best for: Sleep-study dose comparison |
100% elemental / active | 1000–1000 mg | 100% means the isolated amino-acid composition, not brain uptake. Compare declared L-tryptophan mass; meal amino acids can affect transport. Usually tolerated at studied amounts; individual gastrointestinal discomfort remains possible. |
Studied standard [FORM // TRIAL_REFERENCE] 100% means the isolated amino-acid composition, not brain uptake. Compare declared L-tryptophan mass; meal amino acids can affect transport. |
| L-tryptophan with vitamin B6 Best for: Label comparison |
Unstandardized: active content unknown | no comparable trial range | No clinical superiority over pure L-tryptophan is established when B6 status is adequate. Total blend weight is not a valid L-tryptophan amount; comparison unavailable. Usually tolerated at studied amounts; individual gastrointestinal discomfort remains possible. |
Caution [FORM // CHECK_LABEL] No clinical superiority over pure L-tryptophan is established when B6 status is adequate. Total blend weight is not a valid L-tryptophan amount; comparison unavailable. |
| Alpha-lactalbumin / tryptophan-rich whey Best for: Food-matrix research comparison |
Unstandardized: active content unknown | no comparable trial range | Food-protein matrix with different tryptophan-to-LNAA ratio; protein mass is not free L-tryptophan mass. No verified percentage conversion is supplied. Usually tolerated at studied amounts; individual gastrointestinal discomfort remains possible. |
Caution [FORM // CHECK_LABEL] Food-protein matrix with different tryptophan-to-LNAA ratio; protein mass is not free L-tryptophan mass. No verified percentage conversion is supplied. |
Common label traps
- TRAP_01 // NATURAL SEROTONIN REPLACES ANTIDEPRESSANTS
Clinical depression evidence is insufficient and interactions can be serious. - TRAP_02 // 5-HTP IS THE SAME SUPPLEMENT
5-HTP is a distinct downstream metabolite with a different risk and evidence profile; no mg equivalence applies. - TRAP_03 // TRYPTOPHAN DESTROYS REM SLEEP
The dossier does not establish this blanket claim. Its main quantitative signal concerns WASO, not a universal REM effect. - TRAP_04 // IT CAUSED HEART DISEASE IN 60% OF 12000 PEOPLE
The supplied dossier does not substantiate this claim. Documented EMS concerns relate to manufacturing impurities, not that statistic.
Other outcomes studied
Outside the five leaderboard goals. Same evidence levels as above.
- sleep Limited · benefit
WASO SMD -1.08 (95% CI -1.89 to -0.28); only four studies quantitatively pooled. At least 1 g showed a stronger WASO signal, not a universal dose-response prediction.
PMID 33942088 - sleep-null-components Limited · no benefit
Sleep latency, total sleep time and efficiency did not improve significantly in the pooled analysis.
PMID 33942088 - healthy-adult-mood Limited · benefit
Only 4/11 RCTs showed significant mood/emotional differences; 0.14-3 g/day, heterogeneous short protocols, no pooled effect size and no consistent aggression benefit.
PMID 32272859 - clinical-depression Limited · benefit
Older analysis pooled two adequate studies with 64 patients, including one 5-HTP and one L-tryptophan trial: Peto OR 4.1 (95% CI 1.3-13.2), but evidence judged insufficient. Relevant catalog titles are missing; review before publication.
PMID 12169147 PMID 11687048 - pmdd Limited · benefit
One RCT (37 active, 34 placebo), 6 g/day in the luteal phase over three cycles: maximal mood VAS fell 34.5% versus 10.4%, p=0.004. High-dose specialist context, limited replication.
PMID 10023508 - appetite Limited · benefit
A protein-breakfast RCT found less lunch energy intake with alpha-lactalbumin or gelatin/tryptophan matrices. This does not establish isolated tryptophan weight loss or greater daily energy.
PMID 19185957 - depletion-mechanism Limited · benefit
Acute depletion can worsen selected mood/anxiety measures in susceptible or remitted patients; removal experiments do not establish supplementation benefit.
PMID 22491355 PMID 11400999 PMID 10890310 PMID 25781231 - manufacturing-safety Limited · benefit
Review connects eosinophilia-myalgia concerns with manufacturing impurities; exact historical casualty counts are not asserted here.
PMID 37453474
Reader questions
Is 5-HTP better?
There is no universal superiority or dose equivalence. It is a separate supplement, not another form of L-tryptophan.
Can I take it instead of, or immediately after, an SSRI?
Do not change treatment or invent a washout interval. Ask the prescriber about interactions and whether supplementation is appropriate.
Why am I groggy the next day?
Drowsiness is a recognized adverse effect. Avoid driving while impaired and seek review for persistent or severe symptoms.
Does food supply the same thing?
Food provides tryptophan within a protein matrix, with competing amino acids. A protein serving is not equivalent to an isolated-tryptophan trial dose.
Stack interactions
- Danger SSRIs, SNRIs, MAOIs, tricyclics and serotonergic opioids [CAUTION // CLINICAL_REVIEW]
Serotonergic combinations can cause serotonin syndrome; do not self-combine. Review describes clinical features; a fatal multidrug case included L-tryptophan, duloxetine and amitriptyline.
PMID 31523132 PMID 41732713 - Danger Linezolid and metoclopramide [CAUTION // CLINICAL_REVIEW]
A published case describes serotonin syndrome with this combination including tryptophan; linezolid inhibits MAO. Prescriber review is required.
PMID 19828401 - Caution 5-HTP, St Johns wort, SAM-e and other mood stacks [CAUTION // CLINICAL_REVIEW]
Avoid unsupervised stacking of serotonergic agents; exact risks vary and mechanisms alone do not prove every proposed pairwise interaction. - Caution B6 and meal protein/carbohydrate [CAUTION // CLINICAL_REVIEW]
B6 is a pathway cofactor, without proven benefit from extra B6 in replete people. LNAA competition and meal composition affect uptake, but do not define a universally superior meal protocol.
Red flags: interactions and who should avoid it
Interactions
Serotonergic combinations can cause serotonin syndrome; do not self-combine. Review describes clinical features; a fatal multidrug case included L-tryptophan, duloxetine and amitriptyline. A published case describes serotonin syndrome with this combination including tryptophan; linezolid inhibits MAO. Prescriber review is required. Avoid unsupervised stacking of serotonergic agents; exact risks vary and mechanisms alone do not prove every proposed pairwise interaction. B6 is a pathway cofactor, without proven benefit from extra B6 in replete people. LNAA competition and meal composition affect uptake, but do not define a universally superior meal protocol.
Avoid or ask a doctor first if
Do not combine with serotonergic medicines without prescribing-clinician supervision. Avoid unsupervised use in pregnancy/breastfeeding, children, bipolar disorder, serotonin-secreting tumors or a history of eosinophilia-myalgia syndrome. Nausea, dizziness and next-day drowsiness can occur. Agitation with fever, tremor, muscle jerks or autonomic instability requires urgent assessment.
Sources (PubMed, 12)
- The impact of tryptophan supplementation on sleep quality: a systematic review, meta-analysis, and meta-regression.
PMID 33942088 · 2022 · systematic review/meta-analysisWASO SMD -1.08 (95% CI -1.89 to -0.28); only four studies quantitatively pooled. At least 1 g showed a stronger WASO signal, not a universal dose-response prediction.
- A systematic review of the effect of L-tryptophan supplementation on mood and emotional functioning.
PMID 32272859 · 2021 · systematic review/meta-analysisOnly 4/11 RCTs showed significant mood/emotional differences; 0.14-3 g/day, heterogeneous short protocols, no pooled effect size and no consistent aggression benefit.
- A placebo-controlled clinical trial of L-tryptophan in premenstrual dysphoria.
PMID 10023508 · 1999 · randomized controlled trialOne RCT (37 active, 34 placebo), 6 g/day in the luteal phase over three cycles: maximal mood VAS fell 34.5% versus 10.4%, p=0.004. High-dose specialist context, limited replication.
- A breakfast with alpha-lactalbumin, gelatin, or gelatin + TRP lowers energy intake at lunch compared with a breakfast with casein, soy, whey, or whey-GMP.
PMID 19185957 · 2009 · randomized controlled trialA protein-breakfast RCT found less lunch energy intake with alpha-lactalbumin or gelatin/tryptophan matrices. This does not establish isolated tryptophan weight loss or greater daily energy.
- Acute tryptophan depletion increases translational indices of anxiety but not fear: serotonergic modulation of the bed nucleus of the stria terminalis?
PMID 22491355 · 2012 · randomized controlled trialAcute depletion can worsen selected mood/anxiety measures in susceptible or remitted patients; removal experiments do not establish supplementation benefit.
- Tryptophan depletion in SSRI-recovered depressed outpatients.
PMID 11400999 · 2001 · randomized controlled trialAcute depletion can worsen selected mood/anxiety measures in susceptible or remitted patients; removal experiments do not establish supplementation benefit.
- Behavioural effects of acute tryptophan depletion in healthy male volunteers.
PMID 10890310 · 2000 · randomized controlled trialAcute depletion can worsen selected mood/anxiety measures in susceptible or remitted patients; removal experiments do not establish supplementation benefit.
- Serotonin versus catecholamine deficiency: behavioral and neural effects of experimental depletion in remitted depression.
PMID 25781231 · 2015 · randomized controlled trialAcute depletion can worsen selected mood/anxiety measures in susceptible or remitted patients; removal experiments do not establish supplementation benefit.
- Safety concerns regarding impurities in L-Tryptophan associated with eosinophilia myalgia syndrome.
PMID 37453474 · 2023 · narrative reviewReview connects eosinophilia-myalgia concerns with manufacturing impurities; exact historical casualty counts are not asserted here.
- Serotonin Syndrome: Pathophysiology, Clinical Features, Management, and Potential Future Directions.
PMID 31523132 · 2019 · narrative reviewSerotonergic combinations can cause serotonin syndrome; do not self-combine. Review describes clinical features; a fatal multidrug case included L-tryptophan, duloxetine and amitriptyline.
- The interplay between serotonin syndrome and syndrome of inappropriate antidiuresis: a fatal case of acute hyponatremia during treatment with duloxetine, chlorphenamine, amitriptyline, and L-tryptophan.
PMID 41732713 · 2026 · review or clinical study; see title and findingSerotonergic combinations can cause serotonin syndrome; do not self-combine. Review describes clinical features; a fatal multidrug case included L-tryptophan, duloxetine and amitriptyline.
- [Serotonin syndrome due to interaction between linezolid, tryptophan, and metoclopramide].
PMID 19828401 · 2009 · review or clinical study; see title and findingA published case describes serotonin syndrome with this combination including tryptophan; linezolid inhibits MAO. Prescriber review is required.
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