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) — 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.
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.
See how L-Tryptophan compares on grade, dose, and goal in the Evidence Explorer.
