L-tyrosine
Summary
L-tyrosine is a protein amino acid and a building block for catecholamine neurotransmitters. Small, short trials suggest it can blunt stress-related drops in working memory during cold, sleep loss or combat training, but not in the heat. The doses studied were grams at a time, far above typical capsules, and evidence is limited.
Key facts
- A non-essential amino acid found in dietary protein; a precursor of dopamine and noradrenaline[1]
- A rapid evidence review of 10 RCTs and 4 controlled trials found all cognitive-stress studies positive but rated the evidence insufficient for confident recommendations[1]
- No recommendation could be made for physical performance under stress[1]
- Grams per dose: 2 g five times a day, or 150 mg per kg body weight (about 10 g for a 70 kg adult)[3][2]
- Infused N-acetyl-L-tyrosine raised blood tyrosine only 25%, and 56% left in the urine unchanged within 4 hours[6]
- 3 graded human outcomes on this page
- October 11, 2026
How it works
ProposedUnder acute stress, brain catecholamines can be depleted; extra tyrosine is proposed to support their synthesis. This rests mainly on animal work and short human stress studies.[1][2]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Cognition under stress | Grade D | Improved | RCT · n = 21 · 1999 | 2 rows |
| Heat stress | Grade D | No effect | Crossover RCT · n = 8 · 2016 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Memory and tracking during combat training | Improved | Grade D | RCT · n = 21 · 1999 Military cadets on a demanding combat training course Form: Protein-rich drink with tyrosine · Dose: 2 g tyrosine five times daily (10 g/day) · Duration: 6 days The tyrosine group performed better on memory and tracking tasks than the calorie-matched carbohydrate group and had lower systolic blood pressure; mood did not change. | 10230711 (opens PubMed)Source [3] |
| Working memory during cold exposure | Improved | Grade D | Crossover RCT · n = 19 · 2007 Healthy volunteers during two 90-minute cold-water immersions Form: L-tyrosine in a food bar · Dose: 150 mg/kg before each immersion (300 mg/kg total) · Duration: Single test day Cold impaired memory; with tyrosine, correct responses on a match-to-sample memory test rose and study time fell versus placebo. | 17585971 (opens PubMed)Source [2] |
| Cognition and time trial in the heat | No effect | Grade D | Crossover RCT · n = 8 · 2016 Healthy adults doing a loaded military march at 40 °C Form: L-tyrosine drink · Dose: 150 mg/kg · Duration: Single session Heat impaired some cognitive measures, but tyrosine did not reduce the decline or improve the time trial. | 26285023 (opens PubMed)Source [4] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| L-tyrosine | Varies | A single oral 150 mg/kg dose raised serum tyrosine as effectively as a double dose.[4] | Described as relatively benign at 150 mg/kg in a sleep-loss study.[5] | All stress-cognition trials cited here |
| N-acetyl L-tyrosine (NALT) | Varies | Given intravenously, NALT raised blood tyrosine 25% and 56% was excreted unchanged in 4 hours; no oral trials of NALT for cognition were found in the sources cited here.[6] | No form-specific tolerance data in the sources cited here. | Intravenous nutrition research only |
Studied doses
Doses studied in human trials ranged from 150 to 300 mg per kg body weight in a single day (about 10–21 g for a 70 kg adult) to 2 g five times daily for 6 days; all trials were acute or under one week.[2][3][4]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
Who should be careful
- Anyone expecting long-term effects
- Every trial cited here lasted a single day to 6 days, so effects and safety of daily long-term use are unknown.[1]
- Pregnancy and breastfeeding
- Not studied in the trials cited here.[1]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Where to buy L-tyrosine
Products from brands we partner with that contain L-tyrosine. Listing a product is not a claim that it works; check the amount per serving against the doses studied above, and the label for other ingredients.
- SupersmartPaid linkN-Acetyl L-Tyrosine (NALT)3 capsules: 900 mg N-acetyl L-tyrosine; 20 servings. Trials used plain L-tyrosine at 10 g or more per day (150 mg/kg or 2 g five times daily), over 10 times this amount, and NALT converts poorly to tyrosine when infused, so this product does not match the studied form or dose.Shop at Supersmart (opens in new tab)Price and label checked 2026-10-11 on the brand’s site.
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Frequently asked questions
Does L-tyrosine improve focus?
Under acute stress such as cold, sleep loss or combat training, small trials found better working memory; there is little evidence for everyday focus without stress.[1][2]
Is NALT better than L-tyrosine?
There is no oral evidence it is better. Infused NALT raised blood tyrosine only 25%, with over half excreted unchanged.[6]
How much tyrosine did studies use?
Grams per dose: commonly 150 mg per kg body weight, about 10 g for a 70 kg adult, or 2 g five times daily.[2][3]
Does tyrosine help exercise in the heat?
No: in a crossover trial at 40 °C it did not stop the cognitive decline or improve a loaded time trial.[4]
Does tyrosine help with sleep deprivation?
One study during a night of sleep loss found less psychomotor decline and fewer vigilance lapses for about 3 hours after a dose.[5]
Sources
- [1]Tyrosine for Mitigating Stress and Enhancing Performance in Healthy Adult Humans, a Rapid Evidence Assessment of the Literature. Mil Med, 2015. systematic-review
- [2]Tyrosine supplementation mitigates working memory decrements during cold exposure. Physiol Behav, 2007. crossover-RCT
- [3]Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course. Brain Res Bull, 1999. RCT
- [4]Tyrosine Ingestion and Its Effects on Cognitive and Physical Performance in the Heat. Med Sci Sports Exerc, 2016. crossover-RCT
- [5]The effects of tyrosine on cognitive performance during extended wakefulness. Aviat Space Environ Med, 1995. RCT
- [6]N-acetyl-L-tyrosine and N-acetyl-L-cysteine as tyrosine and cysteine precursors during intravenous infusion in humans. Metabolism, 1989. PK-study
What changed
- New monograph: definition, key facts, evidence table, studied doses, safety and FAQ written from the cited abstracts and fact sheets.