Protocols by Charles Sieg

Supplements

L-tyrosine

What the trials say about L-tyrosine for focus under stress, sleep loss, cold, and multitasking, what it does not do, and when it can be risky.

Overall evidence Early18 sourcesReviewed November 5, 2026

Small, short trials, most of them single doses given under stress, tend to show a benefit for working memory; trials in exercise and in older adults found no benefit or a worse result, and the multi-week trials that would test daily use are still missing.

The short version

  • I take L-tyrosine gummies from JOYLI Nutrition. L-tyrosine is an amino acid the body uses to make dopamine and norepinephrine1,2.
  • The pattern across trials: it helps when demanding conditions have temporarily drawn those chemicals down, and it does little otherwise. The benefit shows up under cold, sleep loss, military training, and multitasking, mostly as better working memory1,2,3,4,5,6.
  • Most of that work is small, gave one large dose, and was done in a lab. Most of the stress trials used 150 to 300 mg per kilogram of body weight, and I could not confirm how much one serving of my gummies holds6,3,7,8.
  • It did not help a cycling time trial, and in a study of older adults it did not help response control, with a worse effect on one measure the older the person was9,10.
  • It is not for everyone. The prescribing information for the MAO inhibitor Nardil tells patients taking it not to take L-tyrosine11.

The protocol

This is what the research used, not a prescription. I have not listed my own dose or timing here.

ParameterWhat the research used
Single dose in stress trials150 mg/kg of body weight, given about 1 hour before testing in the multitasking trial6, and 150 mg/kg before each of two 90-minute cold-water immersions, 300 mg/kg in all, in one cold trial3
Higher single dose300 mg/kg in another cold-water trial7
Lower single dose2.0 g in one lab study of working memory12
Sleep loss150 mg/kg in a split dose, 6 hours into about 13 hours of continuous overnight work during one night of lost sleep4
Military courseA protein-rich drink containing 2 g of tyrosine, five daily doses, with testing on day 6 of a combat training course5
Exercise trial (no benefit)25 mg/kg in drinks taken every 30 minutes, starting an hour before a 90-minute ride9
Daily use, safetyUp to 4 g a day for 4 weeks was well tolerated in a crossover trial of 30 healthy men13
TimingNearly all the trials gave one load in a single test session, before or during the stressor, not a daily habit; reviewers say the multi-week trials that would test daily use are missing2

What this means for a gummy: as of November 2026, the maker's home page names the product "L-Tyrosine Gummies 1000MG" and shows no supplement facts, serving size, or servings per container8. I could not confirm from the maker how much tyrosine one serving holds. Most of the stress trials gave 150 mg/kg or more6,3,7,4, and the smallest single dose among these trials that showed a benefit was 2.0 g, in one lab study12. Without the label's numbers, I can't say how the gummies compare with what the trials tested.

Why it works

Tyrosine is the building block for dopamine and norepinephrine. The leading idea, drawn partly from rat studies, is that stress, cold, and sleep loss deplete those chemicals in the brain and extra tyrosine helps replace them2,3. One review sums it up as an effective cognitive enhancer, but only when neurotransmitter function is intact and dopamine or norepinephrine is temporarily depleted1. A second review explains the "buffering" it saw under demanding conditions the same way2. If those chemicals aren't depleted, there is nothing to replace, which fits the null results below.

What the research says

Early Under stress and demanding conditions, working memory. A systematic review of 15 studies, all but one giving a single load, found tyrosine acutely offset declines in working memory and information processing under demanding conditions such as extreme weather or heavy cognitive load2. A rapid evidence assessment of 10 randomized trials and 4 controlled clinical trials gave a weak recommendation for cognitive stress because all the cognitive studies were positive, and judged the evidence insufficient for confident recommendations14. A narrative review reached the same overall read1. I grade this "early," not "strong," because the trials are small and mostly single-dose, and the reviewers themselves ask for larger, multi-week studies2.

Early Multitasking. In 20 people given 150 mg/kg an hour before testing, tyrosine improved working memory accuracy on a battery that stacked several tasks at once, but did not change arithmetic, visual, or auditory performance on that battery, and did nothing on a simpler battery6. A separate lab study in 22 young women given a single 2.0 g dose found a benefit on an N-back working-memory task in the harder 2-back condition but not the easier 1-back one12.

Early Cold. In 19 volunteers, immersions in water of about 50°F (10°C) lowered correct responses on a memory task, and tyrosine at 150 mg/kg before each of two immersions increased them3. In 15 people given 300 mg/kg, performance on a memory task fell 18 percent and marksmanship 14 percent in the cold placebo trial, while the tyrosine trial did not differ from the warm control. The step test dropped 11 percent in both cold trials, so the physical task got no help7.

Early Sleep loss. In a double-blind study of continuous overnight work through one night of lost sleep, tyrosine at 150 mg/kg reduced the usual decline on a psychomotor task and lowered lapse probability on a vigilance task, and the benefit lasted about 3 hours4. In a trial that compared tyrosine with caffeine, phentermine, d-amphetamine, and placebo after a night without sleep, tyrosine was less effective than d-amphetamine but still improved performance on several tests15. A companion paper from the same research group, in 76 healthy men kept awake 40.5 hours, found that tyrosine given after 36 hours awake did not change any sleep measure, though it raised prolactin16.

Early Military stress. In 21 cadets on a combat training course, the tyrosine group (10) did better on a memory task and a tracking task on day 6 than the carbohydrate group (11), and tyrosine lowered systolic blood pressure, with no effect on mood5. It is a small study, and tyrosine arrived inside a protein drink compared with a carbohydrate drink.

Early Who responds. In a randomized trial, people with the T/T version of a dopamine-receptor gene variant (DRD2 C957T) gained more from tyrosine than people with the C/C version, which suggests the benefit may depend on a person's own dopamine function17. That result needs replication.

Early Exercise: no benefit. Nine competitive cyclists rode 90 minutes and then did a time trial. With tyrosine alone the time trial took 32.6 minutes and with placebo 34.4; the carbohydrate drinks were what sped it up (27.1 minutes alone and 26.1 with tyrosine), and the authors concluded tyrosine did not improve time-trial performance9. Across the reviews, most studies found no significant effect on exercise performance2,1.

Early Older adults: no benefit, possibly harm. In 24 healthy adults aged 61 to 72 given 150 mg/kg, tyrosine did not change reactive or proactive inhibition across the group, and the older the person, the more tyrosine worsened proactive slowing compared with placebo10.

The only place I found Rhonda Patrick taking up tyrosine is FoundMyFitness Q&A #52, a members-only episode posted October 11, 2023. Its timeline lists the question "What are your thoughts on supplemental tyrosine?" with six study links, but the page has no show notes or transcript for that answer, so I can't say what she concluded18. Her appearance here does not mean she endorses me or this site.

How I use it

I take L-tyrosine gummies from JOYLI Nutrition8. That is all I have told the site so far.

Where I buy it

I don't list prices because they change. The links are plain product links, with no referral tag.

Cautions

  • MAO inhibitors. The prescribing information for the MAO inhibitor Nardil (phenelzine), in its contraindications section, tells patients taking it not to take sympathomimetic drugs or related compounds, names L-tyrosine among those compounds, and gives the reason: MAO inhibitors may potentiate them and cause a hypertensive crisis11. That label covers Nardil. The 2026 safety trial also excluded people taking MAO inhibitors13. For any other MAO inhibitor, it's a question for the prescriber.
  • Thyroid disease and thyroid medication. The 2026 safety trial excluded people with thyroid disorders, including hyperthyroidism and Graves' disease, did not measure thyroid hormones, and its authors say an effect on thyroid function cannot be completely ruled out13. I did not find a trial in people taking thyroid medication, so I can't say what the combination does. That's a question for the prescriber.
  • The safety data are short and narrow. Up to 4 g a day for 4 weeks showed no dose-related lab abnormalities and no serious adverse events, in healthy men only. The trial was funded by Ajinomoto, two of its four authors work there, and the tyrosine came from Ajinomoto Healthy Supply13.
  • Older adults. One small study found a worse result with age, so I would not assume it helps10.
  • It may do little when you're rested. The strongest signal is under stress, cold, or sleep loss, and a 2015 review says it helps only when dopamine or norepinephrine is temporarily depleted1.

References

  1. Jongkees BJ, Hommel B, Kühn S, Colzato LS. Effect of tyrosine supplementation on clinical and healthy populations under stress or cognitive demands--A review. Journal of Psychiatric Research. 2015;70:50-57.ReviewPubMed 26424423 · DOI

    What it found: Review of tyrosine supplementation in clinical and healthy people. It concludes tyrosine has limited benefit for clinical disorders and for physical exercise, and enhances cognition mainly in short-term stressful or cognitively demanding situations, but only when dopamine or norepinephrine is temporarily depleted and neurotransmitter function is otherwise intact.

    Limits: A narrative review whose abstract gives no doses, sample sizes, or effect sizes, and it was written by a group that also runs tyrosine trials.

  2. Hase A, Jung SE, aan het Rot M. Behavioral and cognitive effects of tyrosine intake in healthy human adults. Pharmacology, Biochemistry, and Behavior. 2015;133:1-6.Systematic reviewPubMed 25797188 · DOI

    What it found: Systematic review of fifteen studies, all but one giving tyrosine as a load during one test session. Most behavioral studies found no significant effect on exercise performance, while cognitive studies found tyrosine acutely offset declines in working memory and information processing under demanding conditions such as extreme weather or heavy cognitive load.

    Limits: Mostly single-dose studies in small samples, and the authors call for larger groups tested over multiple weeks.

  3. Mahoney CR, Castellani J, Kramer FM, Young A, Lieberman HR. Tyrosine supplementation mitigates working memory decrements during cold exposure. Physiology & Behavior. 2007;92(4):575-582.Lab or mechanistic studyPubMed 17585971 · DOI

    What it found: Double-blind within-subject study of 19 volunteers in 35°C water with placebo, about 10°C water with placebo, and about 10°C water with tyrosine (150 mg/kg in a food bar before each of two 90-minute immersions). In the cold, correct responses on a match-to-sample memory task fell (p<.05); with tyrosine they increased (p<.05).

    Limits: Nineteen people tested in a water-immersion lab rather than in real cold exposure, and the abstract does not say the session order was randomized.

  4. Neri DF, Wiegmann D, Stanny RR, Shappell SA, McCardie A, McKay DL. The effects of tyrosine on cognitive performance during extended wakefulness. Aviation, Space, and Environmental Medicine. 1995;66(4):313-319.Randomized trialPubMed 7794222

    What it found: Double-blind study of about 13 hours of continuous nighttime work involving one night of lost sleep. Six hours in, half the participants received 150 mg/kg of tyrosine in a split dose and half a cornstarch placebo; tyrosine reduced the usual decline on a psychomotor task and lowered lapse probability on a vigilance task, with benefits lasting about 3 hours.

    Limits: The abstract does not give the sample size, the benefit was brief, and the authors say other doses and timing still need testing.

  5. Deijen JB, Wientjes CJ, Vullinghs HF, Cloin PA, Langefeld JJ. Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course. Brain Research Bulletin. 1999;48(2):203-209.Randomized trialPubMed 10230711 · DOI

    What it found: Study of 21 cadets in a demanding combat training course: 10 received five daily doses of a protein-rich drink containing 2 g of tyrosine and 11 a carbohydrate-rich drink with the same calories. On day 6 the tyrosine group did better on a memory task and a tracking task and had lower systolic blood pressure, with no effect on mood.

    Limits: Only 21 people, a military setting, and tyrosine was given inside a protein drink compared with a carbohydrate drink, so it is not a clean one-ingredient comparison.

  6. Thomas JR, Lockwood PA, Singh A, Deuster PA. Tyrosine improves working memory in a multitasking environment. Pharmacology, Biochemistry, and Behavior. 1999;64(3):495-500.Lab or mechanistic studyPubMed 10548261 · DOI

    What it found: Twenty participants (10 men and 10 women) did a multiple-task battery and a simple-task battery 1 hour after 150 mg/kg of L-tyrosine or placebo. On the multiple-task battery tyrosine improved working memory accuracy; it did not change arithmetic, visual, or auditory performance there, and it changed nothing on the simple-task battery.

    Limits: Twenty people, a single dose, and a benefit limited to one measure under multitasking demands.

  7. O'Brien C, Mahoney C, Tharion WJ, Sils IV, Castellani JW. Dietary tyrosine benefits cognitive and psychomotor performance during body cooling. Physiology & Behavior. 2007;90(2-3):301-307.Lab or mechanistic studyPubMed 17078981 · DOI

    What it found: Fifteen subjects completed a 35°C control trial and two cold-water trials, one with tyrosine at 300 mg/kg in an energy bar. In the placebo cold trial match-to-sample performance fell 18% (p = 0.02) and marksmanship fell 14% (p = 0.002) versus control; the tyrosine trial did not differ from control. Step-test performance dropped 11% in both cold trials.

    Limits: Fifteen people, one high dose, and no benefit on the physical (step) test.

  8. JOYLI Nutrition. JOYLI Nutrition - Premium Nutrition Supplements Crafted for Your Wellness. joylinutrition.com, November 5, 2026.Product pageRead

    What it found: The maker's home page lists two products named "L-Tyrosine Gummies 1000MG", both linking out to Amazon, and shows no supplement facts, serving size, or servings per container for either.

    Limits: The page gives no label details, so the amount per serving, the serving size, and the other ingredients could not be confirmed from the maker.

  9. Chinevere TD, Sawyer RD, Creer AR, Conlee RK, Parcell AC. Effects of L-tyrosine and carbohydrate ingestion on endurance exercise performance. Journal of Applied Physiology. 2002;93(5):1590-1597.Randomized trialPubMed 12381742 · DOI

    What it found: Nine competitive cyclists rode 90 minutes at 70% of peak oxygen uptake and then did a time trial under four drink conditions, including L-tyrosine at 25 mg/kg. Time-trial times were 32.6 minutes with tyrosine alone and 34.4 minutes with placebo, and the authors concluded tyrosine did not improve cycling time-trial performance.

    Limits: Nine cyclists and one exercise test, with 25 mg/kg drinks every 30 minutes rather than the single large doses of the stress trials, so it does not rule out an effect at those doses.

  10. Bloemendaal M, Froböse MI, Wegman J, Zandbelt BB, van de Rest O, Cools R, et al. Neuro-Cognitive Effects of Acute Tyrosine Administration on Reactive and Proactive Response Inhibition in Healthy Older Adults. eNeuro. 2018;5(2):ENEURO.0035-17.2018.Randomized trialPubMed 30094335 · DOI

    What it found: Double-blind within-subject fMRI study of 24 healthy older adults aged 61 to 72. Tyrosine did not change reactive or proactive inhibition behavior across the group, and older age predicted a greater harmful effect of tyrosine, relative to placebo, on proactive slowing.

    Limits: Twenty-four people, a single session, and the abstract does not report the dose (the full text gives 150 mg/kg).

  11. Parke-Davis Division of Pfizer Inc. NARDIL- phenelzine sulfate tablet, film coated. DailyMed, National Library of Medicine (FDA drug label), June 6, 2025.Regulatory noticeRead

    What it found: The prescribing information for the MAO inhibitor phenelzine (Nardil), updated June 6, 2025. Its contraindications section tells patients taking Nardil not to take sympathomimetic drugs or related compounds, lists L-tyrosine among those related compounds alongside methyldopa, L-dopa, L-tryptophan, and phenylalanine, and gives the risk of hypertensive crises as the reason.

    Limits: A label for one MAO inhibitor, so it does not directly cover other MAO inhibitors.

  12. Colzato LS, Jongkees BJ, Sellaro R, Hommel B. Working memory reloaded: tyrosine repletes updating in the N-back task. Frontiers in Behavioral Neuroscience. 2013;7:200.Randomized trialPubMed 24379768 · DOI

    What it found: Placebo-controlled study of whether L-tyrosine improves updating of working memory in an N-back task. Tyrosine helped performance in the harder 2-back condition but not the easier 1-back condition.

    Limits: The abstract reports no sample size or dose (the full text reports 22 young women and one 2.0 g dose), and a single working-memory task in lab volunteers does not show a real-world effect.

  13. Matsumoto H, Miura N, Naito M, Elango R. Evaluation of the Safety and Tolerability of L-Tyrosine Supplementation in Healthy Adult Men: A Randomized Crossover Trial. Nutrients. 2026;18(12):2020.Randomized trialPubMed 42356406 · DOI

    What it found: Randomized, double-blind, placebo-controlled crossover trial of 30 healthy men given 0, 1, 2, 3, or 4 g a day of L-tyrosine (each man received four of the five doses) with 2-week washouts. Up to 4 g a day for 4 weeks produced no dose-related lab abnormalities and no serious adverse events, and the authors propose 4 g a day as the highest tested dose without observable adverse effects.

    Limits: Healthy men only, 4 weeks, the trial excluded people with thyroid disorders and people taking MAO inhibitors, and it was funded by Ajinomoto, which employs two of the four authors.

  14. Attipoe S, Zeno SA, Lee C, Crawford C, Khorsan R, Walter AR, et al. Tyrosine for Mitigating Stress and Enhancing Performance in Healthy Adult Humans, a Rapid Evidence Assessment of the Literature. Military Medicine. 2015;180(7):754-765.Systematic reviewPubMed 26126245 · DOI

    What it found: Rapid evidence assessment of randomized trials up to October 2012 that included 10 randomized controlled trials and 4 controlled clinical trials. It made no recommendation for tyrosine's effect on physical performance under stress and a weak recommendation in favor of tyrosine for cognitive stress, because all cognitive studies showed a positive effect.

    Limits: A rapid review with a search that stops in 2012, and the authors judged the evidence insufficient for confident recommendations.

  15. Magill RA, Waters WF, Bray GA, Volaufova J, Smith SR, Lieberman HR, et al. Effects of tyrosine, phentermine, caffeine D-amphetamine, and placebo on cognitive and motor performance deficits during sleep deprivation. Nutritional Neuroscience. 2003;6(4):237-246.Randomized trialPubMed 12887140 · DOI

    What it found: Healthy young men were given placebo, tyrosine (150 mg/kg), caffeine (300 mg per 70 kg), phentermine (37.5 mg), or d-amphetamine (20 mg) in the afternoon following overnight sleep deprivation. All drugs improved some measures; tyrosine was less effective than d-amphetamine but still improved performance on several tests.

    Limits: The abstract gives no sample size and no tyrosine-versus-placebo statistics, and sleep deprivation here was one night.

  16. Waters WF, Magill RA, Bray GA, Volaufova J, Smith SR, Lieberman HR, et al. A comparison of tyrosine against placebo, phentermine, caffeine, and D-amphetamine during sleep deprivation. Nutritional Neuroscience. 2003;6(4):221-235.Randomized trialPubMed 12887139 · DOI

    What it found: Seventy-six healthy men aged 18 to 35 took part in a four-day double-blind protocol that included 40.5 hours without sleep and received tyrosine (150 mg/kg), caffeine, phentermine, d-amphetamine, or placebo. Given after 36 hours awake, tyrosine had no significant effect on any sleep measure in recovery sleep, although it increased prolactin release.

    Limits: This paper reports sleep and hormone outcomes, not alertness or thinking performance, and it covers one dose in young men.

  17. Colzato LS, Steenbergen L, Sellaro R, Stock AK, Arning L, Beste C. Effects of l-Tyrosine on working memory and inhibitory control are determined by DRD2 genotypes: A randomized controlled trial. Cortex. 2016;82:217-224.Randomized trialPubMed 27403851 · DOI

    What it found: Double-blind placebo-controlled trial testing whether a DRD2 gene variant (C957T, rs6277) predicts response to tyrosine on a stop-signal task and an N-back task. People with the T/T genotype, linked to lower striatal dopamine, gained more from tyrosine than C/C people.

    Limits: The abstract reports no sample size or dose, and a genotype-by-treatment result like this needs replication.

  18. Patrick R. Q&A #52: Does Lion's Mane Boost Brain Health—and Are Mineral Sunscreens Safe?. FoundMyFitness, October 11, 2023.PodcastListen

    What it found: Rhonda Patrick's members-only Q&A episode. The timeline lists the question "What are your thoughts on supplemental tyrosine?" at 00:13:07, with six study links and no written answer.

    Limits: The episode is members-only and the page has no show notes or transcript on tyrosine, so I confirmed the topic but not what she said.