What is L-Tyrosine?

September 16, 2025 - By DocV

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An amino acid and precursor to dopamine, norepinephrine, and epinephrine (catecholamines).
Plays a role in cognitive performance, stress resilience, and mood regulation, especially under demanding conditions.

Multiple studies show tyrosine can improve cognitive performance when the brain is under stress (e.g., cold, sleep deprivation, multitasking).
Deijen & Orlebeke (1994): Tyrosine improved working memory and tracking tasks in young adults during stress.
Neri et al. (1995, U.S. Army): Tyrosine improved alertness and reduced fatigue during extended wakefulness in military personnel.
Mahoney et al. (2007): Showed tyrosine preserved working memory during multitasking under psychological stress.

Takeaway → Works best when catecholamine levels are taxed, like during stress or fatigue—not as much under normal conditions.

Some evidence tyrosine reduces perceived stress and improves mood in acutely stressful environments.
Shurtleff et al. (1994): Improved mood and performance during a demanding cognitive battery.
Banderet & Lieberman (1989): Tyrosine improved mood and reduced stress in cadets during cold exposure.

Neri et al. (1995): Military personnel stayed more alert with tyrosine despite sleep loss.
Magill et al. (2003): Reported improved vigilance under sleep deprivation.

Results are mixed.
Struder et al. (1998): No consistent improvement in endurance or exercise performance.
Some trials suggest tyrosine may help with thermoregulation in heat or cold exposure.

Tyrosine is a dopamine precursor, so researchers looked at psychiatric conditions.
Depression → No strong benefit in general populations; may help in dopamine-related subtypes.
ADHD → Small trials showed inconsistent results; stimulants are much more effective.
Parkinson’s disease → Limited and weak evidence as a supportive adjunct, not a treatment.

Typical dose range: 100–300 mg/kg body weight daily in divided doses.
- Example: ~7–20 g/day for a 70 kg adult in research trials.
Over-the-counter supplements usually: 500 mg – 2 g per serving.
Often taken before stress, exams, or sleep-deprivation tasks.

Generally well tolerated.
High doses may cause GI upset, headache, or restlessness.
Should be used cautiously in people on thyroid medication or MAO inhibitors (can affect catecholamine metabolism).

Best evidence: Tyrosine helps maintain cognitive performance and mood under stress, fatigue, and sleep deprivation.
Limited evidence: Everyday use for mood, focus, ADHD, or exercise performance.
Safe in typical doses, but more effective as a situational enhancer than a daily “nootropic.”