Supplements

L-Tyrosine

Updated · 23 sources · Editorial policy

L-tyrosine is one of the 20 amino acids used to build proteins. The body also uses it as the raw material for dopamine, norepinephrine and epinephrine, the catecholamine neurotransmitters. It is found in protein-rich foods, the body makes it from phenylalanine, and it is sold as a dietary supplement, mostly for focus and “stress resilience.”

The most important fact is where the evidence actually points. Single large doses have helped working memory in small military and laboratory studies where people were stressed by cold, altitude, sleep loss or multitasking. A 2023 meta-analysis found no effect on endurance performance, and trials found no benefit for strength, depression or phenylketonuria outcomes.

This page summarizes what clinical trials, systematic reviews and regulators report. It is for education only and is not medical advice.

Property Detail
Class Aromatic amino acid; catecholamine precursor
Formula / weight C₉H₁₁NO₃, 181.19 g/mol (PubChem)
Source in the body Diet, or made from phenylalanine (mainly in the liver)
Route Oral (powder, capsules, added to foods)
Doses in cited trials 100–300 mg/kg taken shortly before a test; 1–4 g/day for 4 weeks in a safety trial
Half-life No elimination half-life reported in the sources reviewed; plasma levels peak about 2 h after an oral dose
Key mechanism fact Raises catecholamine synthesis only in neurons that are actively firing
US status Listed food additive (21 CFR 172.320); sold as a dietary supplement
WADA status Not named on the 2026 Prohibited List

What it is

L-tyrosine is (2S)-2-amino-3-(4-hydroxyphenyl)propanoic acid, formula C₉H₁₁NO₃, molecular weight 181.19 g/mol (PubChem). It is phenylalanine with a hydroxyl (-OH) group added to the ring.

The body makes tyrosine by adding that hydroxyl group to phenylalanine. The liver is the main site of this step, and it only runs one way: phenylalanine becomes tyrosine, never the reverse (Matthews, J Nutr 2007). Because of this, tyrosine is classed as a dispensable (nonessential) amino acid (Matsumoto et al., Nutrients 2026). In phenylketonuria (PKU), an inherited disorder in which phenylalanine cannot be converted, people must strictly limit phenylalanine, and tyrosine supply becomes a concern (Remmington and Smith, Cochrane 2021).

Tyrosine not used for protein or neurotransmitters is broken down, ending as fumarate and acetoacetate, which feed into energy metabolism (Matthews, J Nutr 2007).

Why it might affect the brain

The enzyme tyrosine hydroxylase acts on tyrosine in the rate-limiting step of catecholamine synthesis. Unlike most neurotransmitter pathways, it is sensitive to how much substrate is available at normal brain concentrations (Fernstrom and Fernstrom, J Nutr 2007).

The review adds two qualifications:

  • Raising brain tyrosine increases catecholamine production only in neurons that are actively firing.
  • Eating more protein, in one meal or over several days, also raises brain tyrosine.

This is the basis for the main hypothesis in the field. Extra tyrosine may help when demanding conditions drain catecholamines, but it should do little in a rested person.

How it works in the body

The best dose-response data come from a double-blind crossover trial in 17 older adults (aged 60–75) given 100, 150 or 200 mg/kg, and 17 young adults given 150 mg/kg. Plasma tyrosine was measured for 4 hours after dosing (van de Rest et al., Nutrients 2017).

Finding Result
Time to peak (earlier studies, 100–150 mg/kg) About 2 h after ingestion
Rise in plasma tyrosine 5- to 7-fold in this trial; 2- to 3-fold in earlier studies with less precise assays
Dose response in older adults Higher dose gave higher plasma levels at every step (p under 0.001)
Age effect at 150 mg/kg Older adults had higher baseline levels and a larger rise than young adults
Time course Young adults showed no significant fall from 90 to 240 min; levels in older adults fell from 150 min onward

The authors noted that other large neutral amino acids compete with tyrosine for transport into the brain, so the rest of the diet can affect how much of a dose gets there.

In a 4-week safety trial, fasting plasma tyrosine was modestly higher only at the top dose of 4 g/day. Other plasma amino acids did not change (Matsumoto et al., Nutrients 2026).

Regulatory status

  • Food additive. L-tyrosine is one of the amino acids FDA lists as safe to add to foods as a nutrient, under conditions that cap each amino acid as a share of the food’s total protein (21 CFR 172.320).
  • Supplement. It is widely consumed in foods and as a dietary supplement (Matsumoto et al., Nutrients 2026).
  • Sport. L-tyrosine is not named on the WADA 2026 Prohibited List.

What the research shows

Cognition under acute stress

Most of the positive data come from small US military and university studies. Each gave a single large dose and then exposed people to a stressor.

Study Design and n Dose Stressor Main result
Banderet and Lieberman 1989 Double-blind crossover 100 mg/kg 4.5 h of cold plus hypoxia Fewer symptoms, less adverse mood and smaller performance losses, in people who reacted at least averagely to the stress
Thomas et al. 1999 Placebo-controlled; 10 men, 10 women 150 mg/kg, 1 h before Multitasking battery Better working memory accuracy during multitasking; no effect on arithmetic, visual or auditory tasks, or on a simple task battery
Deijen et al. 1999 21 cadets, two groups Protein-rich drink with 2 g tyrosine, five times daily 1 week of combat training Better memory and tracking than a calorie-matched carbohydrate drink; lower systolic blood pressure; no mood effect
Mahoney et al. 2007 Double-blind, within-subject; n = 19 150 mg/kg before each of two cold-water immersions (300 mg/kg total) Water at ≈10 °C Cold impaired memory; tyrosine raised correct responses on a match-to-sample memory test (p under 0.05)

Reviews draw cautious conclusions from this literature:

  • A 2015 rapid evidence assessment found 10 randomized and 4 controlled trials. It gave only a weak recommendation for tyrosine under cognitive stress and said the evidence was insufficient to draw confident conclusions (Attipoe et al., Mil Med 2015).
  • A 2015 narrative review concluded that tyrosine helps cognition only when neurotransmitter function is intact and dopamine or norepinephrine is temporarily depleted, mainly in short-term stressful or demanding situations (Jongkees et al., J Psychiatr Res 2015).

The samples were small and the outcomes were laboratory tasks. A 2015 systematic review of 15 studies noted that all but one tested a single tyrosine load in one session, and called for larger trials lasting several weeks (Hase et al., Pharmacol Biochem Behav 2015).

Cognition in older adults

More is not always better. In the van de Rest trial, load-dependent working memory performance (on the N-back task) declined as the dose went up (p = 0.048). The decline was greatest in those whose plasma tyrosine rose the most (p = 0.035) (van de Rest et al., Nutrients 2017).

Endurance and strength performance

A 2023 systematic review and meta-analysis pooled 10 interventions from 8 studies in physically active people (Solon-Júnior et al., J Sports Sci 2023):

Outcome Effect of tyrosine vs placebo
Time to exhaustion SMD 0.02 (p = 0.94)
Time-trial performance SMD −0.04 (p = 0.85)
GRADE certainty Moderate

SMD is the standardized mean difference; values near zero mean no effect. The authors concluded tyrosine is ineffective for endurance performance.

Individual trials show why early positive results did not hold up:

Study n Dose Test Result
Tumilty et al. 2011 8 men 150 mg/kg, 1 h before Constant-load cycling to exhaustion at 30 °C 80.3 vs 69.2 min (p under 0.01)
Tumilty et al. 2014 7 trained men 150 mg/kg Self-paced time trial at 30 °C 34.8 vs 35.2 min; no difference
Sutton et al. 2005 20 men 150 mg/kg, 30 min before Load carriage, then handgrip, pull-ups, stair stepping No effect on endurance, muscle strength or anaerobic power
Solon-Júnior et al. 2026 12 recreational cyclists 300 mg/kg Cycling to exhaustion after a 60-min mentally fatiguing task About 16% longer time to exhaustion (p = 0.008); authors call it preliminary

The same research group found a benefit in the 2011 trial but not in the 2014 trial, with the same dose and heat. The 2026 trial in mentally fatigued cyclists fits the “depletion” hypothesis, but it is a single 12-person study. None of these trials measured muscle growth.

Depression

In a 4-week randomized, double-blind trial, 65 outpatients with major depression received tyrosine 100 mg/kg/day, imipramine or placebo. Tyrosine raised a norepinephrine metabolite in urine but showed no antidepressant effect (Gelenberg et al., J Affect Disord 1990).

Phenylketonuria

A Cochrane review found three trials with 56 participants. Supplements raised blood tyrosine (mean difference 23.46; 95% CI 12.87–34.05), but no other outcome differed from placebo. The authors concluded that no recommendation can be made for routine use, and they do not plan further updates because the field is no longer active (Remmington and Smith, Cochrane 2021).

Side effects and risks

Tolerability in trials

  • 4-week safety trial. In a randomized, double-blind, placebo-controlled crossover trial, 30 healthy men took 0, 1, 2, 3 or 4 g/day for 4 weeks. There were no dose-related abnormalities in blood counts, chemistry or electrolytes, and no serious adverse events. Mild-to-moderate events were as common as with placebo. The authors proposed 4 g/day as the no-observed-adverse-effect level under these study conditions. Two authors were employees of Ajinomoto, an amino acid manufacturer (Matsumoto et al., Nutrients 2026).
  • Single large doses. No adverse events were reported after single doses up to 200 mg/kg (van de Rest et al., Nutrients 2017).
  • Depression trial. At 100 mg/kg/day for 4 weeks, tyrosine had no side effect that differed significantly from placebo (Gelenberg et al., J Affect Disord 1990).

Long-term safety at the high single doses used in cognition and exercise studies has not been studied.

Blood pressure and heart rate

Results vary by setting. Systolic blood pressure fell in cadets during combat training (Deijen et al. 1999). In the multitasking study, heart rate and blood pressure rose during the tasks (Thomas et al. 1999).

Inherited disorders of tyrosine metabolism

The nitisinone label shows what persistently high tyrosine can do. Nitisinone treats hereditary tyrosinemia type 1 and blocks a step in tyrosine breakdown. Patients must restrict dietary tyrosine and phenylalanine and keep plasma tyrosine under 500 µmol/L. Above that level, the label warns of eye problems (corneal ulcers and opacities, keratitis, light sensitivity), painful thickened skin on the palms and soles, and developmental delay (Orfadin label). In this disorder, tyrosine intake is restricted under medical supervision.

Levodopa

Tyrosine is a large neutral amino acid. The carbidopa-levodopa label states that levodopa competes with certain amino acids for absorption from the gut, and that a high-protein diet may delay and reduce levodopa absorption (Sinemet label). The label does not name tyrosine supplements specifically, and the sources reviewed here include no interaction study.

Key takeaways

  • A building block, not a stimulant. Tyrosine is the raw material for dopamine and norepinephrine, and extra tyrosine increases their synthesis only in neurons that are already firing.
  • Small, situational cognitive benefits. Single doses of 100–300 mg/kg helped working memory in small studies under cold, hypoxia, multitasking or combat training. Reviews describe this evidence as limited.
  • No reliable performance or muscle benefit. A 2023 meta-analysis found no effect on endurance, and a trial in 20 men found no effect on strength or anaerobic power.
  • No benefit for depression or PKU outcomes. A 1990 RCT and a 2021 Cochrane review found no clinical benefit.
  • Well tolerated in short trials. Up to 4 g/day for 4 weeks caused no lab abnormalities, but higher single doses impaired working memory in older adults.
  • Not prohibited in sport. L-tyrosine is a listed US food additive and is not named on the WADA 2026 Prohibited List.

Sources

  1. National Center for Biotechnology Information. PubChem Compound Summary for CID 6057, L-Tyrosine. PubChem.
  2. Matthews DE. An overview of phenylalanine and tyrosine kinetics in humans. J Nutr. 2007;137(6 Suppl 1):1549S–1555S. PubMed.
  3. Fernstrom JD, Fernstrom MH. Tyrosine, phenylalanine, and catecholamine synthesis and function in the brain. J Nutr. 2007;137(6 Suppl 1):1539S–1547S. PubMed.
  4. van de Rest O, Bloemendaal M, de Heus R, et al. Dose-dependent effects of oral tyrosine administration on plasma tyrosine levels and cognition in aging. Nutrients. 2017;9(12):1279. PubMed.
  5. Matsumoto H, Miura N, Naito M, et al. Evaluation of the safety and tolerability of L-tyrosine supplementation in healthy adult men: a randomized crossover trial. Nutrients. 2026;18(12):2020. PubMed.
  6. Food and Drug Administration. 21 CFR 172.320, Amino acids. eCFR.
  7. World Anti-Doping Agency. The 2026 Prohibited List. WADA 2026 Prohibited List.
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  9. Thomas JR, Lockwood PA, Singh A, et al. Tyrosine improves working memory in a multitasking environment. Pharmacol Biochem Behav. 1999;64(3):495–500. PubMed.
  10. Deijen JB, Wientjes CJ, Vullinghs HF, et al. Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course. Brain Res Bull. 1999;48(2):203–209. PubMed.
  11. Mahoney CR, Castellani J, Kramer FM, et al. Tyrosine supplementation mitigates working memory decrements during cold exposure. Physiol Behav. 2007;92(4):575–582. PubMed.
  12. Attipoe S, Zeno SA, Lee C, et al. Tyrosine for mitigating stress and enhancing performance in healthy adult humans, a rapid evidence assessment of the literature. Mil Med. 2015;180(7):754–765. PubMed.
  13. Hase A, Jung SE, aan het Rot M. Behavioral and cognitive effects of tyrosine intake in healthy human adults. Pharmacol Biochem Behav. 2015;133:1–6. PubMed.
  14. Jongkees BJ, Hommel B, Kühn S, et al. Effect of tyrosine supplementation on clinical and healthy populations under stress or cognitive demands—a review. J Psychiatr Res. 2015;70:50–57. PubMed.
  15. Solon-Júnior LJF, Boullosa Alvarez DA, Martinez Gonzalez B, et al. The effect of tyrosine supplementation on whole-body endurance performance in physically active population: a systematic review and meta-analysis including GRADE qualification. J Sports Sci. 2023;41(22):2045–2053. PubMed.
  16. Tumilty L, Davison G, Beckmann M, et al. Oral tyrosine supplementation improves exercise capacity in the heat. Eur J Appl Physiol. 2011;111(12):2941–2950. PubMed.
  17. Tumilty L, Davison G, Beckmann M, et al. Failure of oral tyrosine supplementation to improve exercise performance in the heat. Med Sci Sports Exerc. 2014;46(7):1417–1425. PubMed.
  18. Sutton EE, Coill MR, Deuster PA. Ingestion of tyrosine: effects on endurance, muscle strength, and anaerobic performance. Int J Sport Nutr Exerc Metab. 2005;15(2):173–185. PubMed.
  19. Solon-Júnior LJF, Boullosa D, Dias CV, et al. Effects of L-tyrosine ingestion on endurance performance in mentally fatigued cyclists. Eur J Sport Sci. 2026;26(4):e70150. PubMed.
  20. Gelenberg AJ, Wojcik JD, Falk WE, et al. Tyrosine for depression: a double-blind trial. J Affect Disord. 1990;19(2):125–132. PubMed.
  21. Remmington T, Smith S. Tyrosine supplementation for phenylketonuria. Cochrane Database Syst Rev. 2021;1(1):CD001507. PubMed.
  22. Swedish Orphan Biovitrum. Orfadin (nitisinone) oral suspension prescribing information. DailyMed.
  23. Organon. Sinemet (carbidopa and levodopa) tablets prescribing information. DailyMed.