L-Tyrosine
EVIDENCE: MODERATEAlso sold as: tyrosine, N-acetyl L-tyrosine, NALT
Tyrosine is the building block for dopamine and noradrenaline. Trials using about 100–300 mg per kilogram of body weight (several grams) found it can protect mental performance under stress such as cold or multitasking. It doesn't seem to help in ordinary conditions.
Compiled by iSupplementReviews editorial team ·Researched 2026-10-16 · 3 sources
- Type
- Amino acid
- Studied dose
- 100–300 mg/kg body weight as a single dose (about 7–20 g for a 70 kg adult)
- Best form
- L-tyrosine (better absorbed than N-acetyl tyrosine)
- Our rating
- MODERATE — Several human trials — limits in size, duration, or independence
What is L-tyrosine?
L-tyrosine is an amino acid the body uses to make dopamine, noradrenaline, adrenaline and thyroid hormones. It is sold for focus and stress resilience.
Other names and forms
Tyrosine, L-tyrosine, N-acetyl L-tyrosine (NALT). NALT converts to tyrosine less efficiently.
Where does L-tyrosine come from?
Protein foods, and the body makes it from another amino acid, phenylalanine.
How does L-tyrosine work in the body?
When the brain is using up dopamine and noradrenaline quickly, as under acute stress, extra tyrosine may help keep levels up. That is the proposed reason it helps only under demanding conditions (Jongkees et al., 2015).
What is L-tyrosine claimed to do?
Improve focus, mood, energy and stress resilience; some products add weight or metabolism claims.
What does the research show?
| Claim | Evidence | Dose studied | Verdict |
|---|---|---|---|
| Cognition under acute stress | Several small RCTs, review | 100–300 mg/kg single dose | Moderate positive |
| Cognition in normal conditions | Same trials | — | Little effect |
| Mood or depression | Few trials | — | Weak |
| Weight or blood sugar | None | — | Insufficient |
Under stress
Tyrosine protected working memory and attention during cold, sleep loss and multitasking in short trials. Jongkees et al. (2015) reviewed these studies and found benefits mainly when demands were high. In one example, Mahoney et al. (2007) found tyrosine reduced the working-memory decline caused by cold exposure. Amino-acid precursors in general act on brain chemistry only at substantial doses (Jenkins et al., 2016).
What dose was studied?
| Goal | Dose | Duration |
|---|---|---|
| Cognition under stress | 100–300 mg/kg body weight | Single dose |
Side effects
Nausea, headache, heartburn at high doses.
Drug interactions
- MAO inhibitors: can trigger dangerous blood-pressure spikes (major).
- Levothyroxine and thyroid conditions: may add to thyroid hormone levels (moderate).
- Levodopa: may compete for absorption (moderate).
- Stimulants: effects may add up (minor, theoretical).
Who should not take L-tyrosine?
People on MAO inhibitors, with overactive thyroid, or with melanoma (a theoretical concern noted in clinical references).
What the authorities say
Tyrosine is a normal dietary amino acid; regulators do not recognize it as a treatment for any condition.
What to know about L-tyrosine
Tyrosine can support mental performance during acute stress at doses of several grams. Small amounts sit far below the doses studied.
Frequently asked questions about L-Tyrosine
Does tyrosine improve focus?
Only under stress, according to the research. A 2015 review found tyrosine helped working memory and attention during cold exposure, sleep loss or multitasking, at doses of several grams. It did not help much in normal conditions.
How much tyrosine do people take?
Studies used 100–300 mg per kilogram of body weight in one dose, which is several grams for most adults.
Is tyrosine safe?
Short-term use is generally well tolerated. People on MAO inhibitors or thyroid medicine should avoid it unless a doctor says otherwise.
References
- [1]Jongkees BJ et al. — Effect of tyrosine supplementation on clinical and healthy populations under stress or cognitive demands: a review (J Psychiatr Res, 2015)
- [2]Jenkins TA et al. — Influence of Tryptophan and Serotonin on Mood and Cognition with a Possible Role of the Gut-Brain Axis (Nutrients, 2016)
- [3]Mahoney CR et al. — Tyrosine supplementation mitigates working memory decrements during cold exposure (Physiol Behav, 2007)
Products we reviewed containing L-Tyrosine
Based on recorded labels or seller-described formulas. Inclusion does not establish a match to the strains, preparations or amounts studied here; check each review's disclosure limits.