Full profile
| Also known as | Tyrosine, N-Acetyl-L-Tyrosine (NALT) |
|---|---|
| Best for | Cognitive resilience under acute stress · Focus during sleep deprivation or long shifts · Performance under heavy multitasking load |
| Evidence grade | Grade B — Moderate — several human trials, some mixed results |
| Studied dose range | ~2 g acutely in cognition studies; 100–150 mg/kg (~7–12 g) in sleep-deprivation and cold-stress paradigms. |
| Time to effect | Acute — effects reported ~30–60 minutes after a single dose, taken pre-task. |
| Best form | Plain (free-form) L-tyrosine. N-Acetyl-L-Tyrosine (NALT) converts poorly when taken orally and raises plasma tyrosine far less. |
| Food sources | Cheese (parmesan), Soy, Beef, Chicken, Fish, Eggs, Nuts and seeds |
Evidence, honestly graded
A systematic review (Jongkees 2015) and several acute-dose RCTs show ~2 g improves working memory and cognitive flexibility, but mainly when catecholamines are depleted by stress or demand; it does not reliably lift baseline in rested adults. Graded B for the stress/depletion use case, closer to C for baseline enhancement.
See the full grading rubric — study type, replication, population match, and dose adequacy — in The Evidence Standard.
958 licensed natural health products in Health Canada's LNHPD list L-Tyrosine as a medicinal ingredient.
That makes L-Tyrosine 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
- Generally well tolerated at studied doses
- Occasional GI upset or headache
- Jitteriness or overstimulation at high doses
Who should avoid it or check first
- Hyperthyroidism or Graves' disease without review
- Pregnant or breastfeeding without clinician guidance
- History of melanoma without review
Interactions
- Contraindicated with MAOI antidepressants (hypertensive-crisis risk)
- May interact with thyroid medication and levodopa — separate levodopa doses and discuss with a clinician
Stacks well with
Use caution stacking with
- Stimulant medications without clinician guidance
What to look for on a label
- Frame the benefit around demanding or high-stress days, not everyday enhancement — that matches the evidence.
- Look for plain L-tyrosine; the acetylated form (NALT) is poorly converted when taken orally.
References
- Jongkees 2015, J Psychiatric Research — review. Tyrosine helps mainly when catecholamines are depleted by stress or demand, not at baseline. PMID 26424423; doi:10.1016/j.jpsychires.2015.08.014. Educational, not a product claim.
- Colzato 2013, Front Behav Neurosci — N-back RCT. ~2 g tyrosine improved working-memory updating in healthy young adults. PMID 24379768; doi:10.3389/fnbeh.2013.00200.
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.
- 2026-07-05New profile
Initial profile published at Grade B: acute-dose RCTs improve working memory and cognitive flexibility mainly when catecholamines are depleted by stress or demand, not at rested baseline.
See how L-Tyrosine compares on grade, dose, and goal in the Evidence Explorer.
