L-Tyrosine
Research Reliability -
An amino acid precursor to dopamine, norepinephrine, and thyroid hormones that supports focus, mood, and stress response.
Appetite
Mood
Sleep
L-Tyrosine
Description
L-Tyrosine is a non-essential amino acid that serves as the direct precursor to the catecholamine neurotransmitters dopamine, epinephrine, and norepinephrine, as well as thyroid hormones T3 and T4. Its cognitive benefits are most pronounced under conditions of stress, sleep deprivation, or extreme physical exertion, where catecholamine depletion can impair motivation, mental performance, and working memory. Research in military and cognitively demanding contexts shows tyrosine supplementation can sustain performance under these challenging conditions. It is commonly taken before high-stress events or demanding cognitive work.
Effects
First dose
sharper focus under stress within an hour
Same day
Situational
How It Feels
You feel this most when stressed, tired, or under cognitive load: a steadier, more resilient focus within the hour. On a well-rested day the effect is muted, since it tops up depleted dopamine precursors rather than boosting a full tank. Take on an empty stomach.
Evidence
Evidence Strength
Preliminary (limited / small human data)
Caveats
Benefit appears concentrated in situations of acute stress, cold exposure, or sleep deprivation, not general everyday cognitive enhancement.
Usage
Commonly Referenced Starting Amount
500 mg/day
Commonly Referenced Amount
Trials use roughly 100–150 mg per kg body weight (commonly 2–12 g total) for acute cognitive performance under stress or sleep deprivation specifically — it's less clearly useful outside those conditions
Referenced Upper Limit
No upper limit has been established
Onset
30–60 min (acute cognitive)
Biomarkers to Track
Subjective
(Daily)
Mental focus under stress (1–10)
Motivation and drive score
Mood and energy levels
Objective
(Quarterly)
Salivary cortisol (AM level)
Thyroid TSH and free T3/T4
Plasma catecholamines (specialty)
Generally safe. It interacts with thyroid medication and MAOI antidepressants.
People on thyroid meds or MAOIs, and those with hyperthyroidism.
Taking it with food (it competes with protein) and expecting an effect when well-rested rather than stressed.
Disclaimer
This information is for educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure, or prevent any disease. Consult a qualified healthcare provider before starting any new supplement, especially if you are pregnant, nursing, taking medication, or managing a health condition.
Jongkees BJ et al. (2015). Journal of Psychiatric Research. Review (tyrosine and cognitive performance under stress). PMID: 26424423.
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