Full profile
| Also known as | Tryptophan |
|---|---|
| Best for | Sleep-onset support (evening use) · Evening wind-down · Conservative mood-balance support |
| Evidence grade | Grade C · Limited: early or small human trials |
| Studied dose range | Sleep trials used ~1–2 g at night. Regulatory note: Health Canada classifies oral L-tryptophan as a natural health product only up to 220 mg per dose/day; above that it is regulated as a drug. |
| Time to effect | Acute for sleep-onset (same night); any mood effect over roughly 2 weeks. |
| Best form | Pharmaceutical-grade L-tryptophan with documented purity and manufacturing controls; the EMS episode is why source purity matters. |
| Food sources | Turkey and poultry, Eggs, Dairy, Nuts and seeds, Soy |
Evidence, honestly graded
Limited. Small double-blind trials report modest reductions in sleep-onset time (Demisch 1987; Wang 2016), and the Cochrane review of tryptophan and 5-HTP for depression found a signal versus placebo but judged only 2 of 108 trials high enough quality to include (Shaw 2001), which is insufficient to be conclusive. There are no modern large RCTs. The 1989–90 eosinophilia-myalgia syndrome (EMS) outbreak was traced to a contaminant from one manufacturer's process (Belongia 1990), not to tryptophan itself: a purity lesson, not a property of the molecule. Graded C.
See the full grading rubric (study type, replication, population match, and dose adequacy) in The Evidence Standard.
517 natural health products with an active licence in Health Canada's LNHPD list L-Tryptophan as a medicinal ingredient.
That makes L-Tryptophan a recognized, licensable medicinal ingredient in Canada, regulated by Health Canada's Natural and Non-prescription Health Products Directorate, which issues each licensed natural health product a Natural Product Number (NPN). Search the LNHPD to verify.
Side effects
- Drowsiness
- Nausea or GI upset
- Lightheadedness or headache
Who should avoid it or check first
- Taking SSRIs, SNRIs, MAOIs, or other serotonergic drugs (serotonin-syndrome risk)
- Pregnancy or breastfeeding (insufficient data)
- History of eosinophilia-myalgia or scleroderma-like symptoms
Interactions
- Serious serotonin-syndrome risk with SSRIs, SNRIs, MAOIs, triptans, tramadol, dextromethorphan, and other serotonergic agents; this caution must be prominent
- Additive sedation with CNS depressants and alcohol
Stacks well with
- Melatonin (evening slot)
Use caution stacking with
- Any serotonergic medication or supplement without clinician guidance
- 5-HTP (redundant serotonergic precursor)
What to look for on a label
- Carry a prominent "do not combine with antidepressants / serotonergic drugs" caution.
- Respect Health Canada's 220 mg/dose natural-health-product ceiling; the sleep-studied gram doses fall in drug territory in Canada.
References
- Shaw K, Turner J, Del Mar C (2001). Cochrane Database of Systematic Reviews, (3):CD003198Signal favoring treatment over placebo, but evidence insufficient to be conclusive.
- Wang D, Li W, Xiao Y, et al. (2016). Medicine (Baltimore), 95(28):e4135Improved insomnia scores; no effect on mental symptoms.
- Belongia EA, Hedberg CW, Gleich GJ, et al. (1990). New England Journal of Medicine, 323(6):357–365EMS linked to a manufacturing contaminant, not the molecule.
Grades and studied doses are our conservative reading of the human research, shown for education. They are not product claims, and a studied dose is not a recommended dose.
Revision history
Every change to this ingredient's evidence status, dated and explained. The full cross-library log lives at Evidence Updates.
- 2026-07-12New profile
New profile at Grade C for sleep/mood-adjacent roles, with conservative interaction cautions.
See how L-Tryptophan compares on grade, dose, and goal in the Evidence Explorer.
