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Supplements/Amino Acid

L-Tryptophan

Essential amino acid precursor to serotonin and melatonin.

Mood & AnxietySleep & Recovery

Overview

Essential amino acid precursor to serotonin and melatonin.

Natural sources
  • Turkey
  • Eggs
  • Cheese
  • Oats
Common forms
  • L-Tryptophan

Forms & variants of L-Tryptophan

Different chemical forms of L-Tryptophan behave differently. Browse each form's mechanism, bioavailability, and best-use context.

Sleep dose
L-Tryptophan (Sleep)

Direct serotonin/melatonin precursor for nocturnal use.

Mechanism of action

Hydroxylated to 5-HTP then decarboxylated to serotonin; competes with BCAAs for BBB transport.

Pathways
  • · Serotonin synthesis
  • · Kynurenine pathway
Neurotransmitters
  • · Serotonin

Effects on the body

Supports
Serotonin synthesis
Supports
Sleep onset

Organ system effects

Brain & CNS

Carbohydrate intake increases tryptophan brain entry.

Evidence-based benefits

Improves sleep latency and mood

Moderate evidence

Potential side effects

Common
  • · Drowsiness
Rare
    Serious
    • · Eosinophilia-myalgia (historical contaminated batch)

    Drug interactions

    SSRIs / MAOIs / triptans
    Serotonin syndrome risk.
    severe

    Safety & non-supplemental interactions

    Educational summary — always confirm with your clinician or pharmacist before starting, stopping, or combining with prescription therapy.

    Avoid / monitor with these medications
    • ·Alcohol, benzodiazepines, opioids, sedating antihistamines (additive CNS depression)

    Supplement interactions

    Pairs well with

    None listed.

    Avoid combining with

    No specific avoidances listed.

    Dosing & bioavailability

    Typical dose
    1–3 g before bed

    Where to buy

    Affiliate-style search links to reputable retailers. We don't endorse specific brands — verify third-party testing (USP, NSF, Informed Sport) before purchase.

    Amino Acid
    L-Tryptophan
    Amazon
    Wide selection · fast shipping
    Amino Acid
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    iHerb
    Global delivery · curated brands
    Amino Acid
    L-Tryptophan
    Thorne
    Practitioner-grade · NSF tested

    Scientific evidence (8)

    Systematic reviewExamine.com Supplement Database · 2023

    L-Tryptophan: pharmacology, clinical evidence, and safety — narrative review

    Examine.com Research Team

    Curated narrative review of human and preclinical evidence for L-Tryptophan, including mechanism, typical dosing, and safety considerations.

    Key findings

    Best-supported outcome: Improves sleep latency and mood (evidence: moderate). Additional outcomes and limitations summarized in the full profile.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: L-Tryptophan — Improves sleep latency and mood

    Live PubMed search

    Live results for "L-Tryptophan Improves sleep latency and mood" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching L-Tryptophan and "Improves sleep latency and mood". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: L-Tryptophan — randomized controlled trial

    Live PubMed search

    Live results for "L-Tryptophan randomized controlled trial" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching L-Tryptophan and "randomized controlled trial". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: L-Tryptophan — meta-analysis

    Live PubMed search

    Live results for "L-Tryptophan meta-analysis" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching L-Tryptophan and "meta-analysis". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: L-Tryptophan — pharmacokinetics

    Live PubMed search

    Live results for "L-Tryptophan pharmacokinetics" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching L-Tryptophan and "pharmacokinetics". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: L-Tryptophan — safety adverse events

    Live PubMed search

    Live results for "L-Tryptophan safety adverse events" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching L-Tryptophan and "safety adverse events". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: L-Tryptophan — dose response

    Live PubMed search

    Live results for "L-Tryptophan dose response" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching L-Tryptophan and "dose response". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewGoogle Scholar · 1970

    Google Scholar: L-Tryptophan — clinical evidence

    Live Scholar search

    Cross-database citation index for L-Tryptophan as it relates to "clinical evidence".

    Key findings

    Includes preprints, theses, and journal articles. Useful for tracking citation counts and follow-on work.

    Open study
    Educational use only. This profile is not medical advice. Consult a qualified healthcare professional before starting any supplement, especially if you take prescription medication or have a chronic condition.