L-Tyrosine
Also known as: Tyrosine, 4-hydroxyphenylalanine, L-Tyr
Effective Dosage
2000 mg single dose based on available studies; No established daily dose
What the Science Says
L-Tyrosine is an amino acid your body uses to make dopamine, norepinephrine, and other catecholamines — brain chemicals involved in focus, motivation, and stress response. In small clinical trials, a single 2g dose modestly improved reaction time and reduced missed responses during demanding cognitive tasks like the Stroop test. One study also found it may lower physiological arousal (heart rate, pupil response) and speed up decision-making without hurting accuracy. Effects appear most relevant under conditions of mental stress or fatigue.
What It Doesn't Do
Won't eliminate stress — studies show it doesn't lower cortisol, salivary stress markers, or anxiety scores. Not a proven endurance booster — the cycling study data was incomplete in the provided research. No evidence it builds muscle or burns fat. Not a treatment for Parkinson's disease or any neurological condition. Don't expect dramatic mood lifts from a single dose.
Evidence-Based Benefits
L-Tyrosine is an amino acid that plays a crucial role in the production of neurotransmitters, including dopamine and norepinephrine. Research indicates that it may help improve cognitive performance under stress and enhance mood in certain situations.
Strong EvidenceEffective at: 500-2000 mg daily
Source: auto-research
Absorption & Bioavailability
Unknown from provided studies — no pharmacokinetic data was included in the available papers
Red Flags to Watch For
- Very high doses used in studies (300 mg/kg body weight) — far above what most supplements provide, making label doses potentially ineffective
- Evidence is mixed and based on small trials (n=28 to n=80); results may not apply broadly
- People taking thyroid medications or MAO inhibitors should consult a doctor before use — tyrosine is a precursor to thyroid hormones and catecholamines
- Most cognitive benefits observed only under acute stress conditions — everyday use without a stressor may show no effect
Products Containing L-Tyrosine
See how L-Tyrosine is used in these analyzed products:
Research Sources
- PubMed
- NIH DSLD
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-04-06