tuneTypical Dose
100–150 mg/kg acute in clinical paradigms
Amino Acid
L-Tyrosine
4-Hydroxy-L-Phenylalanine (L-Tyrosine)
Evidence TierCWADA NOT PROHIBITED
watchEffect Window
Acute effects within 1–2 hours. Sustained benefit not yet established.
check_circleCompliance
WADA NOT PROHIBITED
Overview
Clinical Summary
L-tyrosine is an amino acid precursor to dopamine and norepinephrine. It is used to preserve cognitive performance under acute stressors such as sleep loss, cold exposure, or high workload.
Evidence shows tyrosine helps maintain working memory, vigilance, and cognitive flexibility during acute stressors that deplete catecholamines. Benefits are less consistent under normal conditions. Minority research explores antidepressant effects with mixed results and limited modern support. Practical benefit is most likely during demanding tasks when sleep restricted or under environmental stress.
Precursor to catecholamine pathways, likely to support neurotransmitter synthesis when systems are acutely depleted, rather than producing sustained tonic upregulation in baseline conditions.
Outcomes
What This Is Expected To Influence
Primary Outcomes
- Acute improvement in selected stress-dependent cognitive tasks at 1–2h post-dose.
- No durable ADHD symptom reduction demonstrated in available long-term clinical evidence.
Secondary Outcomes
- Context-dependent cognitive flexibility effects (multitask settings).
- Minimal evidence for broad mood or stimulant-like benefits in non-stressed populations.
Safety
Contraindications and Interactions
Contraindications
- Pregnancy
- Lactation
- Hyperthyroidism
- MAOI therapy
- Major unstable cardiac/psychiatric disease
Side effects
- Headache
- Nausea
- Heartburn
- Insomnia
- Fatigue
- Irritability
Interactions
- Thyroid hormone replacement
- MAOI therapy
- Levodopa/carbidopa pathways
- Thyroid-active supplement stacks
Avoid if
- Pregnancy or lactation without clinician guidance
- Untreated hypertension or unstable palpitations
- Thyroid-active illness
- Active mania/anxiety instability
- Poorly monitored stimulant or amino-acid stacks
Evidence
Study-level References
l-tyrosine-SRC-001Double-blind crossover clinical trial.
Sourceopen_in_newDeijen JB, Orlebeke JF. 1994. Brain Res Bull. PMID: 8293316, DOI: 10.1016/0361-9230(94)90200-3.
Population: 16 healthy adults, acute noise-stress tasks, 100 mg/kg single-dose L-tyrosine vs placebo.
Key findings: Selective improvement in 2 stress-sensitive cognitive tasks at 1 hour. Minimal change in other physiologic variables.
Notes: Small sample size and acute, task-specific design.
Paper content
Selective improvement in 2 stress-sensitive cognitive tasks at 1 hour; minimal change in other physiologic variables.
l-tyrosine-SRC-002Double-blind randomized controlled trial.
Sourceopen_in_newThomas JR et al. 1999. Pharmacol Biochem Behav. PMID: 10548261, DOI: 10.1016/S0091-3057(99)00094-5.
Population: 20 healthy adults, multiple-task vs simple-task battery, 150 mg/kg acute tyrosine vs placebo.
Key findings: Improved working-memory performance under multitask load. No broad effect across all tested tasks.
Notes: Small cohort, moderate task/method dependence.
Paper content
Improved working-memory performance under multitask load; no broad effect across all tested tasks.
l-tyrosine-SRC-003Open trial (clinical).
Sourceopen_in_newReimherr FW et al. 1987. Am J Psychiatry. PMID: 3300376, DOI: 10.1176/ajp.144.8.1071.
Population: 12 adults with attention deficit disorder, residual type; 8-week exposure.
Key findings: Early response (~2 weeks) in many participants, then tolerance by week 6 and no durable ADHD benefit.
Notes: Unblinded, no comparator, high susceptibility to placebo and expectation effects.
Paper content
Early response (~2 weeks) in many participants, then tolerance by week 6 and no durable ADHD benefit.
l-tyrosine-SRC-004Narrative/systematic-style review of clinical and healthy populations.
Sourceopen_in_newJongkees BJ et al. 2015. J Psychiatr Res review. PMID: 26424423, DOI: 10.1016/j.jpsychires.2015.08.014.
Population: Aggregated stress and cognitive studies in healthy and disorder groups.
Key findings: Concludes tyrosine can help cognition under acute stress/depletion, with limited evidence in clinical disorders.
Notes: Heterogeneous protocols, small acute studies, and limited direct clinical-endpoint data.
Paper content
Concludes tyrosine can help cognition under acute stress/depletion, with limited evidence in clinical disorders.
l-tyrosine-SRC-005Regulatory risk assessment / evidence review.
Sourceopen_in_newFrøyland et al. 2020. European Journal of Nutrition & Food Safety. DOI: 10.9734/ejnfs/2020/v12i830269.
Population: Human and animal safety reports; Norwegian framework assessment of supplement-dose intakes.
Key findings: Suggests potential adverse-effect concern at 1250–2000 mg/day supplement doses, especially due limited long-term human data and MOE constraints.
Notes: Not a therapeutic efficacy study. Evidence relies on sparse clinical trials plus toxicology modeling.
Paper content
Suggests potential adverse-effect concern at 1250–2000 mg/day supplement doses, especially due limited long-term human data and MOE constraints.
l-tyrosine-SRC-006Randomized, double-blind, placebo-controlled, within-subject crossover trial.
Sourceopen_in_newMathar D, Erfanian Abdoust M, Marrenbach T, Tuzsus D, Peters J. The catecholamine precursor Tyrosine reduces autonomic arousal and decreases decision thresholds in reinforcement learning and temporal discounting. PLoS Comput Biol. 2022;18(12):e1010785. doi:10.1371/journal.pcbi.1010785. PMID:36548401.
Population: Healthy young male adults.
Dose protocol: Single acute dose of 2 g L-tyrosine in crossover design
Key findings: Reduced response times and decision thresholds in reinforcement learning and temporal discounting tasks. Enhanced model-based control and reduced autonomic arousal.
Notes: Small sample (n=28), male-only, acute dosing. Extends tyrosine evidence beyond traditional military stress paradigms.
Paper content
This double-blind crossover RCT tested a single 2 g dose of L-tyrosine versus placebo in 28 healthy young men. Tyrosine consistently reduced response times across reinforcement learning and temporal discounting tasks without impairing accuracy. Computational modeling showed attenuated decision thresholds and enhanced model-based control. Physiological measures indicated increased pupil dilation variability and reduced heart rate, suggesting reduced autonomic arousal. The study extends the tyrosine-cognition literature beyond traditional stress paradigms by showing effects on value-based decision-making processes in non-stressed healthy adults.
l-tyrosine-SRC-007Randomized, double-blind, placebo-controlled trial with three arms.
Sourceopen_in_newMcAllister MJ, Martaindale MH, Dillard CC, McCullough R. Impact of L-theanine and L-tyrosine on markers of stress and cognitive performance in response to a virtual reality based active shooter training drill. Stress. 2024;27(1):2375588. doi:10.1080/10253890.2024.2375588. PMID:38975711.
Population: Healthy young adults exposed to an acute stress paradigm.
Dose protocol: Single dose of 2000 mg L-tyrosine before VR acute stress challenge
Key findings: Fewer missed Stroop responses under acute stress. No change in physiological stress markers.
Notes: Three-arm design (tyrosine, theanine, placebo). Supports selective cognitive benefit under stress without physiological stress modulation.
Paper content
This three-arm RCT tested 2000 mg L-tyrosine, 200 mg L-theanine, and placebo in 80 young adults exposed to a virtual reality active shooter drill as an acute mental stressor. L-tyrosine did not reduce salivary stress biomarkers, heart rate, or state anxiety. However, the L-tyrosine group showed significantly fewer missed responses on the Stroop cognitive interference task compared to placebo, suggesting a selective benefit for attentional control under acute stress without modifying the physiological stress response itself. The study supports the pattern seen in earlier military stress trials where tyrosine preserves cognitive performance under demanding conditions.