L-Tyrosine
11 benefits mapped to clinical evidence across supplements.
Dose per serving from products
3,453 products in our catalogue print how much L-Tyrosine a serving holds.
Most common: 500 mg to 1 g, 27% of 3,453 products.
| Dose per serving | Products |
|---|---|
| 25 mg or less | 134 |
| 25 mg to 50 mg | 198 |
| 50 mg to 100 mg | 348 |
| 100 mg to 250 mg | 475 |
| 250 mg to 500 mg | 904 |
| 500 mg to 1 g | 940 |
| 1 g to 2.5 g | 408 |
| over 2.5 g | 46 |
Dose per serving from research
17 study groups in 7 studies say how much L-Tyrosine participants took a day.
These are the doses the studies gave. They are not a recommendation.
Most common: 100 mg/kg to 250 mg/kg, 29% of 17 study groups.
| Daily dose | Study groups |
|---|---|
| 2.5 mg/kg to 5 mg/kg | 2 |
| 5 mg/kg to 10 mg/kg | 3 |
| 10 mg/kg to 25 mg/kg | 2 |
| 25 mg/kg to 50 mg/kg | 1 |
| 50 mg/kg to 100 mg/kg | 3 |
| 100 mg/kg to 250 mg/kg | 5 |
| over 250 mg/kg | 1 |
Commonly used together
19 of 34 study groups took L-Tyrosine with something else. Shown: what 3 or more different studies gave.
What was given together, not what works together.
| Taken with | Study groups |
|---|---|
| Phenylalanine | 11 |
| Essential Amino Acids | 6 |
| Caffeine | 5 |
Benefit Evidence
Learning ↑, depletion ↓
Dopamine precursor shifts
+38% variance, improved learning
Catecholamine depletion: stress↓ resilience
Tyrosine/L-DOPA: stress↑ resilience
+16% vasoconstriction
Motivation↓, cognition↓
Reward response↓, vigilance↓
Prolactin↑, dopamine↓
Learning ↑, depletion ↓
Dopamine precursor shifts
+38% variance, improved learning
Catecholamine depletion: stress↓ resilience
Tyrosine/L-DOPA: stress↑ resilience
+16% vasoconstriction
Motivation↓, cognition↓
Reward response↓, vigilance↓
Prolactin↑, dopamine↓
Research sources
Productivity (42)
- Increased dopamine availability magnifies nicotine effects on cognitive control: A pilot study
PubMed ID: 32133910
Observed improvements in working memory accuracy and reduced switch cost indicate better acute task performance on cognitive tasks.
- Effects of ingesting a pre-workout dietary supplement with and without synephrine for 8Â weeks on training adaptations in resistance-trained males
PubMed ID: 28096757
Randomized trial showed greater Stroop performance and bench press 1RM with the pre‑workout supplement containing N‑Acetyl‑L‑Tyrosine — direct task performance improvements, though multi‑ingredient.
- The relationship between neurotransmission-related amino acid blood concentrations and neuropsychological performance following acute exercise
PubMed ID: 35227132
Blood tyrosine increases after intense exercise associated with better performance on cognitive tests (task performance support).
- Cognitive and Mood Effects of a Nutrient Enriched Breakfast Bar in Healthy Adults: A Randomised, Double-Blind, Placebo-Controlled, Parallel Groups Study
PubMed ID: 29215606
Nutrient bar produced acute improvements on cognitive tasks (attention, working memory) indicating better task performance; tyrosine present but attribution uncertain.
- Branched-chain amino acids enhance the cognitive recovery of patients with severe traumatic brain injury
PubMed ID: 16181934
Raised tyrosine accompanied faster cognitive recovery post‑injury, implying improved task performance in a clinical setting.
- Effects of tyrosine, phentermine, caffeine D-amphetamine, and placebo on cognitive and motor performance deficits during sleep deprivation
PubMed ID: 12887140
Randomized trial showed better performance on memory, reasoning and vigilance tasks after tyrosine in sleep‑deprived men.
- Dopamine and light: effects on facial emotion recognition
PubMed ID: 28633582
Direct finding: APTD increased speed (faster reaction times) to sad faces — strongest direct evidence in the dataset linking tyrosine manipulation to faster reaction time (task- and emotion-specific; small N).
- Effects of serotonin depletion and dopamine depletion on bimodal divided attention
PubMed ID: 30295116
Study reported significant differences in auditory reaction time after manipulating dopamine/serotonin precursors—direct relevance.
- Preliminary evidence for an association between intake of high-fat high-sugar diet, variations in peripheral dopamine precursor availability and dopamine-dependent cognition in humans
PubMed ID: 33270945
Depletion impaired working memory and affected reinforcement learning in some groups—task performance impact.
- Cerebrospinal and plasma amino acid concentrations after administration of i.v. glycyl-glutamine and glycyl-tyrosine containing amino acid solutions in humans
PubMed ID: 8865110
CNS tyrosine availability is necessary for any task performance effects mediated by catecholamines — mechanistic support.
- Clinical efficacy of Sinemet CR 50/200 versus Sinemet 25/100 in patients with fluctuating Parkinson's disease. An open, and a double-blind, double-dummy, multicenter treatment evaluation. The Dutch Sinemet CR Study Group
PubMed ID: 1327609
Sinemet CR reduced off-periods and improved clinical ratings, enhancing daily function.
- Multicenter study of cabergoline, a long-acting dopamine receptor agonist, in Parkinson's disease patients with fluctuating responses to levodopa/carbidopa
PubMed ID: 8105422
Cabergoline reduced disability and percent off time, improving daily activities in PD.
- The effects of L-dihydroxyphenylalanine on alertness and mood in alpha-methyl-para-tyrosine-treated healthy humans. Further evidence for the role of catecholamines in arousal and anxiety
PubMed ID: 8526970
Strong human evidence that restoring catecholamine synthesis (L‑dopa) reduces sleepiness and negative mood — plausible translation to daily productivity via improved alertness/energy.
- Entacapone enhances the response to levodopa in parkinsonian patients with motor fluctuations. Nomecomt Study Group
PubMed ID: 9818851
Entacapone increased on‑time (~+1.4 h) and decreased off‑time — improved daily functional time.
- Tolcapone improves motor function in parkinsonian patients with the "wearing-off" phenomenon: a double-blind, placebo-controlled, multicenter trial
PubMed ID: 9591523
Tolcapone reduced off time and improved motor function and UPDRS, translating to better daily task performance in PD.
- Tolcapone in stable Parkinson's disease: efficacy and safety of long-term treatment. Tolcapone Stable Study Group
PubMed ID: 9591521
Tolcapone improved ADLs and motor scores over months — direct evidence for increased functional/daily productivity in PD.
- Entacapone is beneficial in both fluctuating and non-fluctuating patients with Parkinson's disease: a randomised, placebo controlled, double blind, six month study
PubMed ID: 12876237
Entacapone increased ON time and decreased OFF time — more productive daytime hours expected from sustained dopaminergic effect.
- Employment, medical absenteeism, and disability perception in Parkinson's disease: A pilot double-blind, randomized, placebo-controlled study of entacapone adjunctive therapy
PubMed ID: 17044084
Entacapone added to levodopa associated with far fewer sick days and better self-reported disability — direct productivity signal.
- Placebo-controlled, double-blind dose-finding study of entacapone in fluctuating parkinsonian patients
PubMed ID: 17094103
Entacapone increased patients' daily on-time by ~1.4 hours — a direct signal of increased productive awake time.
- Fourteen-year final report of the randomized PDRG-UK trial comparing three initial treatments in PD
PubMed ID: 18579806
Long-term levodopa associated with better long-term disability/physical function, supporting daily productivity.
- Quality of life in early Parkinson's disease treated with levodopa/carbidopa/entacapone
PubMed ID: 18846551
Entacapone added to levodopa improved QoL and ADL and nonmotor domains that translate to daily productivity benefits.
- Double-blind trial of levodopa/carbidopa/entacapone versus levodopa/carbidopa in early Parkinson's disease
PubMed ID: 19058133
Large RCT showed modest but significant improvements in UPDRS parts II+III and ADL measures with LCE — directly supports daily productivity gains.
- [Direct switch from conventional levodopa to stalevo (levodopa/carbidopa/entacapone) improves quality of life in Parkinson's disease: results of an open-label clinical study]
PubMed ID: 19156087
Switching to levodopa/carbidopa/entacapone prolonged ON periods and improved QoL in fluctuating patients — more productive time awake.
- New approach to the rehabilitation of post-stroke focal cognitive syndrome: effect of levodopa combined with speech and language therapy on functional recovery from aphasia
PubMed ID: 19268976
Levodopa before language therapy improved speech fluency and repetition vs placebo — clear task performance improvement.
- Immediate versus delayed switch from levodopa/carbidopa to levodopa/carbidopa/entacapone: effects on motor function and quality of life in patients with Parkinson's disease with end-of-dose wearing off
PubMed ID: 21843110
Immediate switch to LCE produced measurable motor and QoL gains that can translate to better daily task performance.
- Effects of L-dopa during auditory instrumental learning in humans
PubMed ID: 23285070
Single‑dose L‑dopa modulated auditory cortex and response‑speed patterns — direct link to reaction speed.
- [The optimization of using levodopa in patients with Parkinson's disease: results of the OPTIMA study]
PubMed ID: 23250605
Large observational study reported improved motor and some non‑motor symptoms and ADLs after levodopa optimization—supports productivity gains.
- Continuous intrajejunal infusion of levodopa-carbidopa intestinal gel for patients with advanced Parkinson's disease: a randomised, controlled, double-blind, double-dummy study
PubMed ID: 24361112
Continuous levodopa infusion reduced OFF time and increased useful ON time—clear clinical improvement in daily functional time in PD.
- Genetic variation in the human brain dopamine system influences motor learning and its modulation by L-Dopa
PubMed ID: 23613810
Controlled study showed L‑Dopa improved skilled motor learning and altered motor cortex plasticity—direct evidence of improved task performance with increased dopamine.
- Differential, but not opponent, effects of L -DOPA and citalopram on action learning with reward and punishment
PubMed ID: 24232442
Levodopa reduced Pavlovian bias in go/no‑go learning, altering task-learning performance (directly task-related).
- Effects of dopaminergic modulation on automatic semantic priming: a double-blind study
PubMed ID: 24099637
Dopaminergic drugs changed rapid semantic priming speeds—supports faster stimulus processing.
- A randomized trial of inhaled levodopa (CVT-301) for motor fluctuations in Parkinson's disease
PubMed ID: 27090868
Inhaled levodopa improved motor UPDRS and reduced OFF time → likely faster motor responses in PD (moderate‑strong indirect evidence for reaction speed).
- Dopaminergic manipulations affect the modulation and meta-modulation of movement speed: Evidence from two pharmacological interventions
PubMed ID: 39182625
Human dopamine manipulations and PD ON/OFF comparisons showed lower dopamine states reduce movement speed—relevant to reaction/movement speed.
- Impact of L-theanine and L-tyrosine on markers of stress and cognitive performance in response to a virtual reality based active shooter training drill
PubMed ID: 38975711
Direct evidence: L‑tyrosine reduced missed answers on the Stroop during a stress drill, showing improved performance on a cognitive task.
- Sleep deprivation and impaired cognition. Possible role of brain catecholamines
PubMed ID: 1356024
AMPT ± sleep deprivation impaired cognition/sleepiness → indirect evidence catecholamines support daily cognitive functioning/productivity.
- Effects of catecholamine depletion on alertness and mood in rested and sleep deprived normal volunteers
PubMed ID: 8099791
AMPT increased sleepiness/impairment, implying that intact tyrosine→catecholamine function is important for maintaining productivity (indirect evidence).
- Antidopaminergic effects of dietary tyrosine depletion in healthy subjects and patients with manic illness
PubMed ID: 11581118
Dietary depletion changed dopamine activity and reduced psychostimulant effects; implies tyrosine availability influences performance on dopamine-dependent tasks.
- Reward processing after catecholamine depletion in unmedicated, remitted subjects with major depressive disorder
PubMed ID: 19393989
Direct finding: AMPT-induced catecholamine depletion slowed reward-related RT — strong inverse evidence that catechol augmentation (via tyrosine) could speed RT.
- Food for creativity: tyrosine promotes deep thinking
PubMed ID: 25257259
Convergent thinking is an objective task measure; L‑tyrosine produced a statistically significant acute improvement in this performance domain.
- Dose-Dependent Effects of Oral Tyrosine Administration on Plasma Tyrosine Levels and Cognition in Aging
PubMed ID: 29168741
N‑back is a task performance measure; study directly reports dose‑dependent effects on high‑load task performance (impairment at higher doses in older adults).
- Dopamine depletion effects on cognitive flexibility as modulated by tDCS of the dlPFC
PubMed ID: 31494070
Direct finding: acute tyrosine/phenylalanine depletion produced slower reaction times—strong evidence that tyrosine availability affects RT.
- Tyrosine negatively affects flexible-like behaviour under cognitively demanding conditions
PubMed ID: 31521870
RCT directly assessed cognitive performance (flexibility) under high cognitive load — highly relevant to task performance but showed impairment with tyrosine in that context.
Focus & concentration (24)
- Sleep deprivation and impaired cognition. Possible role of brain catecholamines
PubMed ID: 1356024
AMPT ± sleep deprivation produced marked cognitive deficits → indirect evidence catecholamines support sustained attention.
- Continuous intrajejunal infusion of levodopa-carbidopa intestinal gel for patients with advanced Parkinson's disease: a randomised, controlled, double-blind, double-dummy study
PubMed ID: 24361112
Continuous levodopa infusion reduced OFF time and increased useful ON time—likely to improve ability to engage in exercise for PD patients.
- Impact of L-theanine and L-tyrosine on markers of stress and cognitive performance in response to a virtual reality based active shooter training drill
PubMed ID: 38975711
Direct L‑tyrosine trial: fewer missed Stroop responses during a stress drill, indicating improved attentional focus under stress.
- Effects of catecholamine depletion on alertness and mood in rested and sleep deprived normal volunteers
PubMed ID: 8099791
AMPT catecholamine depletion increased sleepiness and impaired cognition, implying tyrosine→catecholamines support focus (indirect evidence).
- Increased dopamine availability magnifies nicotine effects on cognitive control: A pilot study
PubMed ID: 32133910
Single-dose L-tyrosine improved working memory accuracy and modulated cognitive control (supports acute focus enhancement).
- Tyrosine negatively affects flexible-like behaviour under cognitively demanding conditions
PubMed ID: 31521870
Concentration-related cognitive performance was tested; tyrosine impaired cognitive flexibility under high load — relevant and suggests potential harm for concentration in demanding tasks.
- Dopamine depletion effects on cognitive flexibility as modulated by tDCS of the dlPFC
PubMed ID: 31494070
Acute tyrosine/phenylalanine depletion slowed reaction time and impaired task switching—supports tyrosine's role in sustaining cognitive focus.
- Dose-Dependent Effects of Oral Tyrosine Administration on Plasma Tyrosine Levels and Cognition in Aging
PubMed ID: 29168741
Direct cognitive test (N‑back) related to attention/focus; higher tyrosine doses impaired high‑load performance in older adults (relevance high though effect was negative).
- Food for creativity: tyrosine promotes deep thinking
PubMed ID: 25257259
Convergent thinking improvement reflects enhanced ability to concentrate on a single correct solution or task.
- Reward processing after catecholamine depletion in unmedicated, remitted subjects with major depressive disorder
PubMed ID: 19393989
AMPT (catecholamine depletion) slowed RT/increased depressive signs — inverse evidence suggests tyrosine (a catechol precursor) may aid focus.
- Antidopaminergic effects of dietary tyrosine depletion in healthy subjects and patients with manic illness
PubMed ID: 11581118
Dietary tyrosine removal lowered dopamine activity and reduced psychostimulant effects; implies tyrosine helps maintain dopamine-linked focus.
- Effects of ingesting a pre-workout dietary supplement with and without synephrine for 8Â weeks on training adaptations in resistance-trained males
PubMed ID: 28096757
Directly tested in resistance‑trained males using a pre‑workout supplement containing N‑Acetyl‑L‑Tyrosine; showed stronger short‑term strength and cognitive test gains in exercise context (best direct exercise‑relevant evidence).
- The relationship between neurotransmission-related amino acid blood concentrations and neuropsychological performance following acute exercise
PubMed ID: 35227132
Acute high‑intensity exercise raised blood tyrosine and correlated with better cognitive tests (supports focus-related cognition).
- Cognitive and Mood Effects of a Nutrient Enriched Breakfast Bar in Healthy Adults: A Randomised, Double-Blind, Placebo-Controlled, Parallel Groups Study
PubMed ID: 29215606
Acute multi‑nutrient bar containing 279 mg L‑tyrosine improved attention measures (RVIP), but many co‑ingredients—moderate attribution to tyrosine.
- Branched-chain amino acids enhance the cognitive recovery of patients with severe traumatic brain injury
PubMed ID: 16181934
IV BCAA raised blood tyrosine and sped cognitive recovery after severe brain injury — direct evidence that increased tyrosine can improve attention/focus (clinical, moderate strength).
- Effects of tyrosine, phentermine, caffeine D-amphetamine, and placebo on cognitive and motor performance deficits during sleep deprivation
PubMed ID: 12887140
Randomized study in sleep‑deprived healthy men showed improved running memory, logical reasoning and visual vigilance—direct evidence of improved focus under sleep loss.
- Effect of Supplementation of a Whey Peptide Rich in Tryptophan-Tyrosine-Related Peptides on Cognitive Performance in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Study
PubMed ID: 30011836
Whey peptides containing Tyr‑Trp motifs improved verbal fluency/attention in fatigued subjects—indirect evidence tyrosine‑containing peptides can support focus.
- Effects of serotonin depletion and dopamine depletion on bimodal divided attention
PubMed ID: 30295116
Direct depletion study showing dopamine‑precursor manipulation affects divided attention/auditory reaction time—supports tyrosine role in focus.
- Cerebrospinal and plasma amino acid concentrations after administration of i.v. glycyl-glutamine and glycyl-tyrosine containing amino acid solutions in humans
PubMed ID: 8865110
IV dipeptide raised plasma and small CSF tyrosine — strong evidence tyrosine can reach CNS to potentially support focus.
- The effects of L-dihydroxyphenylalanine on alertness and mood in alpha-methyl-para-tyrosine-treated healthy humans. Further evidence for the role of catecholamines in arousal and anxiety
PubMed ID: 8526970
Catecholamine depletion increased sleepiness and negative mood and L‑dopa reversed this — strong mechanistic evidence that boosting catecholamine synthesis (downstream of tyrosine) supports focus.
- Entacapone is beneficial in both fluctuating and non-fluctuating patients with Parkinson's disease: a randomised, placebo controlled, double blind, six month study
PubMed ID: 12876237
Entacapone + levodopa increased daily ON time (more dopaminergic 'on' time plausibly supports better focus).
- Ropinirole is effective on motor function when used as an adjunct to levodopa in Parkinson's disease: STRONG study
PubMed ID: 17618525
Adding ropinirole to levodopa improved motor and ADL scores, likely aiding exercise-related focus/performance.
- Double-blind trial of levodopa/carbidopa/entacapone versus levodopa/carbidopa in early Parkinson's disease
PubMed ID: 19058133
Motor/ADL improvements in a large trial indicate enhanced capacity to undertake and focus on exercise/activity.
- Effects of L-dopa during auditory instrumental learning in humans
PubMed ID: 23285070
Single-dose L‑dopa increased auditory cortical activity and altered response speed—mechanistically relevant to focus/attention.
Alertness (20)
- Effects of L-dopa during auditory instrumental learning in humans
PubMed ID: 23285070
Neural activation and altered responding after L‑dopa suggest increased sensory processing/alertness.
- Long-term effect of initiating pramipexole vs levodopa in early Parkinson disease
PubMed ID: 19433655
Epworth Sleepiness Scale differences in long trial indicate levodopa/pramipexole groups differed in daytime sleepiness — supports alertness effect.
- Study of istradefylline in patients with Parkinson's disease on levodopa with motor fluctuations
PubMed ID: 18831530
Istradefylline added to levodopa reduced OFF time, increasing ON/alert periods.
- Placebo-controlled, double-blind dose-finding study of entacapone in fluctuating parkinsonian patients
PubMed ID: 17094103
Entacapone increased mean daily on-time by ~1.4 hours — practical evidence for improved wakeful functioning.
- Entacapone is beneficial in both fluctuating and non-fluctuating patients with Parkinson's disease: a randomised, placebo controlled, double blind, six month study
PubMed ID: 12876237
Adding entacapone increased ON time by ~1.3 h/day — directly relevant to daytime wakeful function.
- Rapid onset of action of levodopa in restless legs syndrome: a double-blind, randomized, multicenter, crossover trial
PubMed ID: 10617168
Large, multisite crossover showed rapid sleep/ daytime benefit from levodopa — good indirect evidence for wakefulness improvement.
- The effects of L-dihydroxyphenylalanine on alertness and mood in alpha-methyl-para-tyrosine-treated healthy humans. Further evidence for the role of catecholamines in arousal and anxiety
PubMed ID: 8526970
Direct human experiment: catecholamine synthesis blockade produced sleepiness that was reversed with L‑dopa — strong evidence that catecholamine precursors/supporting dopamine synthesis enhance alertness.
- Neurotransmitter-precursor-supplement intervention for detoxified heroin addicts
PubMed ID: 22684569
The combined precursor supplement significantly improved insomnia in detoxified subjects (direct sleep/wake benefit), but tyrosine's individual effect cannot be isolated.
- Dopamine depletion effects on cognitive flexibility as modulated by tDCS of the dlPFC
PubMed ID: 31494070
Depletion worsened reaction time and cognitive flexibility, consistent with reduced alertness when tyrosine is low.
- Reward processing after catecholamine depletion in unmedicated, remitted subjects with major depressive disorder
PubMed ID: 19393989
Catecholamine depletion reduced cognitive/affective performance — supports role of catechols in alertness (inverse evidence).
- Antidopaminergic effects of dietary tyrosine depletion in healthy subjects and patients with manic illness
PubMed ID: 11581118
Dietary tyrosine depletion reduced dopamine activity; suggests tyrosine aids dopaminergic alertness, but direct alertness measures absent.
- Effects of catecholamine depletion on alertness and mood in rested and sleep deprived normal volunteers
PubMed ID: 8099791
Pharmacologic catecholamine depletion increased sleepiness, supporting the role of the tyrosine→catecholamine pathway in maintaining alertness (indirect evidence).
- Cerebrospinal and plasma amino acid concentrations after administration of i.v. glycyl-glutamine and glycyl-tyrosine containing amino acid solutions in humans
PubMed ID: 8865110
Demonstrated CNS availability of tyrosine — supports potential to enhance alertness via catecholamine synthesis.
- Effects of tyrosine, phentermine, caffeine D-amphetamine, and placebo on cognitive and motor performance deficits during sleep deprivation
PubMed ID: 12887140
Tyrosine improved vigilance and reasoning after prolonged wakefulness, supporting increased alertness in that context.
- Branched-chain amino acids enhance the cognitive recovery of patients with severe traumatic brain injury
PubMed ID: 16181934
Raised tyrosine correlated with faster cognitive recovery — clinically relevant evidence for enhanced alertness/activation.
- Cognitive and Mood Effects of a Nutrient Enriched Breakfast Bar in Healthy Adults: A Randomised, Double-Blind, Placebo-Controlled, Parallel Groups Study
PubMed ID: 29215606
Reported increases in subjective alertness after the nutrient bar containing L‑tyrosine (acute effect; multi‑ingredient).
- Effects of ingesting a pre-workout dietary supplement with and without synephrine for 8Â weeks on training adaptations in resistance-trained males
PubMed ID: 28096757
Pre‑workout product containing N‑Acetyl‑L‑Tyrosine improved cognitive test performance consistent with increased alertness; confounded by caffeine and other ingredients.
- Impact of L-theanine and L-tyrosine on markers of stress and cognitive performance in response to a virtual reality based active shooter training drill
PubMed ID: 38975711
Improved accuracy under stress suggests enhanced cognitive alertness, though physiological alertness markers were unchanged.
- Sleep deprivation and impaired cognition. Possible role of brain catecholamines
PubMed ID: 1356024
AMPT increased sleepiness and cognitive impairment → indirect evidence catecholamine synthesis (tyrosine pathway) supports alertness.
- Continuous intrajejunal infusion of levodopa-carbidopa intestinal gel for patients with advanced Parkinson's disease: a randomised, controlled, double-blind, double-dummy study
PubMed ID: 24361112
Continuous LCIG reduced OFF time and increased useful ON time, likely improving daytime wakefulness in advanced PD patients.
Learning (24)
- Sleep deprivation and impaired cognition. Possible role of brain catecholamines
PubMed ID: 1356024
AMPT + sleep deprivation produced marked cognitive impairment → strong indirect evidence that catecholamine synthesis (dependent on tyrosine) is crucial for learning and cognition under pressure.
- The relationship between neurotransmission-related amino acid blood concentrations and neuropsychological performance following acute exercise
PubMed ID: 35227132
Acute physiological stress (intense exercise) increased tyrosine and was associated with improved cognitive performance—strongest direct support for performance under pressure.
- Branched-chain amino acids enhance the cognitive recovery of patients with severe traumatic brain injury
PubMed ID: 16181934
Faster recovery of cognition with higher tyrosine in TBI patients implies improved capacity to learn/perform under challenging conditions (clinical, indirect to healthy stress contexts).
- The effects of a branched chain amino acid mixture supplemented with tryptophan on biochemical indices of neurotransmitter function and decision-making
PubMed ID: 15696331
Large BCAA drink that substantially lowered tyrosine availability directly altered risky decision behavior — strong evidence that tyrosine availability affects decision making.
- Effects of tyrosine, phentermine, caffeine D-amphetamine, and placebo on cognitive and motor performance deficits during sleep deprivation
PubMed ID: 12887140
Study context (prolonged wakefulness) is an acute pressureor stressor; tyrosine improved reasoning and memory under that pressure.
- Preliminary evidence for an association between intake of high-fat high-sugar diet, variations in peripheral dopamine precursor availability and dopamine-dependent cognition in humans
PubMed ID: 33270945
Shows working‑memory impairment from precursor depletion and changes in reinforcement learning—relevant to learning when challenged.
- Cerebrospinal and plasma amino acid concentrations after administration of i.v. glycyl-glutamine and glycyl-tyrosine containing amino acid solutions in humans
PubMed ID: 8865110
CNS tyrosine uptake demonstrates basis for catecholamine-mediated decision processes — mechanistic support.
- The effects of L-dihydroxyphenylalanine on alertness and mood in alpha-methyl-para-tyrosine-treated healthy humans. Further evidence for the role of catecholamines in arousal and anxiety
PubMed ID: 8526970
L‑dopa reversed AMPT-induced cognitive/affective impairment — supports the interpretation that adequate catecholamine tone aids decision-related cognitive processes.
- Levodopa: faster and better word learning in normal humans
PubMed ID: 15236398
Short course of levodopa in healthy volunteers improved speed and retention of new word learning — a direct dopaminergic effect supporting learning under challenging conditions; moderately strong indirect evidence for tyrosine→dopamine pathway.
- Dopamine receptor D4 polymorphism predicts the effect of L-DOPA on gambling behavior
PubMed ID: 19914604
L‑DOPA influenced gambling choices in DRD4 7‑repeat carriers — direct evidence that dopaminergic augmentation alters decision processes in at least some people.
- New approach to the rehabilitation of post-stroke focal cognitive syndrome: effect of levodopa combined with speech and language therapy on functional recovery from aphasia
PubMed ID: 19268976
Levodopa enhanced gains from language therapy — direct evidence that dopaminergic augmentation can improve learning in rehabilitation settings.
- Abnormal bidirectional plasticity-like effects in Parkinson's disease
PubMed ID: 21742734
Levodopa altered LTP‑like plasticity measures — directly relevant mechanistic evidence for learning/plasticity under challenge.
- l-DOPA changes ventral striatum recruitment during motor sequence learning in Parkinson's disease
PubMed ID: 22343069
Levodopa reduced ventral putamen recruitment and was linked to worse early motor sequence learning—direct evidence that dopaminergic manipulation affects learning, sometimes negatively.
- Dopamine restores reward prediction errors in old age
PubMed ID: 23525044
L‑DOPA increased learning rate and restored nucleus accumbens reward prediction signals—directly supports improved learning, especially when baseline performance is poor.
- Differential, but not opponent, effects of L -DOPA and citalopram on action learning with reward and punishment
PubMed ID: 24232442
Randomized dopamine manipulation changed action×valence learning (Pavlovian coupling) relevant to learning in demanding/pressure situations.
- Bidirectional modulation of reward-guided decision making by dopamine
PubMed ID: 40439740
L‑DOPA increased the influence of reward magnitude/probability on choices—clear evidence of dopaminergic effects on decision parameters.
- Impact of L-theanine and L-tyrosine on markers of stress and cognitive performance in response to a virtual reality based active shooter training drill
PubMed ID: 38975711
Trial used a stress drill and showed preserved cognitive performance with L‑tyrosine—applicable to performance/learning under pressure though learning per se was not directly measured.
- Effects of catecholamine depletion on alertness and mood in rested and sleep deprived normal volunteers
PubMed ID: 8099791
Catecholamine depletion produced mood and vigilance deficits, suggesting preserved catecholamine synthesis supports decision capacity (indirect inference).
- Antidopaminergic effects of dietary tyrosine depletion in healthy subjects and patients with manic illness
PubMed ID: 11581118
Dietary tyrosine manipulation affected dopamine signaling and psychostimulant responses; supports an indirect role in learning under stress.
- Reward processing after catecholamine depletion in unmedicated, remitted subjects with major depressive disorder
PubMed ID: 19393989
AMPT worsened reward-related RT and mood in remitted MDD, indicating catechol depletion impairs performance under challenge — inverse support for tyrosine aiding learning under pressure.
- Food for creativity: tyrosine promotes deep thinking
PubMed ID: 25257259
Convergent thinking improvement maps onto improved decision/problem‑solving processes; evidence is directly supportive for that cognitive domain.
- Dopamine depletion effects on cognitive flexibility as modulated by tDCS of the dlPFC
PubMed ID: 31494070
Depletion impacted perseverative errors (task switching), indicating tyrosine availability is important for cognitive flexibility/adaptability.
- Tyrosine negatively affects flexible-like behaviour under cognitively demanding conditions
PubMed ID: 31521870
Directly relevant: study measured cognitive flexibility (a key component of mental adaptability) under high load; found tyrosine worsened flexibility — high relevance but indicates impairment rather than benefit.
- Increased dopamine availability magnifies nicotine effects on cognitive control: A pilot study
PubMed ID: 32133910
L-tyrosine modulated task-switching costs (reduced switch cost), indicating improved aspects of cognitive flexibility/adaptability.
Energy & Fatigue (19)
- Effects of tyrosine, phentermine, caffeine D-amphetamine, and placebo on cognitive and motor performance deficits during sleep deprivation
PubMed ID: 12887140
Tyrosine attenuated cognitive declines on multiple tests after sleep loss, consistent with reduced subjective/functional mental fatigue.
- Reward processing after catecholamine depletion in unmedicated, remitted subjects with major depressive disorder
PubMed ID: 19393989
AMPT-induced catechol depletion increased depressive symptoms and slowed RT, consistent with increased mental fatigue when catechol synthesis is impaired.
- Dopamine depletion effects on cognitive flexibility as modulated by tDCS of the dlPFC
PubMed ID: 31494070
Slower reaction times with depletion are consistent with increased mental fatigue when tyrosine is low.
- Impact of L-theanine and L-tyrosine on markers of stress and cognitive performance in response to a virtual reality based active shooter training drill
PubMed ID: 38975711
L‑tyrosine reduced missed responses during a stress drill, consistent with reduced cognitive fatigue under acute stress.
- Sleep deprivation and impaired cognition. Possible role of brain catecholamines
PubMed ID: 1356024
AMPT and sleep deprivation increased sleepiness and cognitive impairment → indirect evidence catecholamines reduce mental fatigue.
- Effects of catecholamine depletion on alertness and mood in rested and sleep deprived normal volunteers
PubMed ID: 8099791
AMPT increased sleepiness and subjective impairment, suggesting that preserved catecholamine synthesis (linked to tyrosine) combats mental fatigue.
- Antidopaminergic effects of dietary tyrosine depletion in healthy subjects and patients with manic illness
PubMed ID: 11581118
Dietary tyrosine removal reduced dopamine activity and psychostimulant responses; supports a role in preventing dopamine-related mental fatigue.
- Psychoneuroendocrine effects of combined thyroxine and triiodothyronine versus tyrosine during prolonged Antarctic residence
PubMed ID: 18274206
Significant mood benefits in a stressful winter environment suggest reduced mental fatigue as a plausible effect.
- Long-term effect of initiating pramipexole vs levodopa in early Parkinson disease
PubMed ID: 19433655
Lower Epworth Sleepiness Scale scores in levodopa-treated groups are consistent with reduced daytime fatigue.
- Fatigue in levodopa-naive subjects with Parkinson disease
PubMed ID: 18695158
Large randomized trial: levodopa-treated patients showed less worsening of fatigue during washout — direct evidence.
- Study of istradefylline in patients with Parkinson's disease on levodopa with motor fluctuations
PubMed ID: 18831530
Istradefylline reduced OFF time vs placebo, likely reducing daytime mental fatigue.
- Rapid onset of action of levodopa in restless legs syndrome: a double-blind, randomized, multicenter, crossover trial
PubMed ID: 10617168
Strong RLS benefit with immediate daytime quality improvement — reasonable indirect evidence for reduced mental fatigue.
- The effects of L-dihydroxyphenylalanine on alertness and mood in alpha-methyl-para-tyrosine-treated healthy humans. Further evidence for the role of catecholamines in arousal and anxiety
PubMed ID: 8526970
AMPT increased sleepiness and L‑dopa reversed it — direct evidence that restoring catecholamine synthesis reduces subjective sleepiness/mental fatigue.
- Cerebrospinal and plasma amino acid concentrations after administration of i.v. glycyl-glutamine and glycyl-tyrosine containing amino acid solutions in humans
PubMed ID: 8865110
Clear demonstration of CNS tyrosine availability — provides biological plausibility that supplementation could reduce mental fatigue via catecholamine synthesis.
- Effect of Supplementation of a Whey Peptide Rich in Tryptophan-Tyrosine-Related Peptides on Cognitive Performance in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Study
PubMed ID: 30011836
Whey peptides improved attention and reduced errors in high‑fatigue subgroup—indirect evidence Tyr motifs can reduce mental fatigue.
- Effects of ingesting a pre-workout dietary supplement with and without synephrine for 8Â weeks on training adaptations in resistance-trained males
PubMed ID: 28096757
Pre‑workout product produced measurable cognitive/strength uplifts consistent with increased subjective/functional mental energy; causality for tyrosine uncertain.
- The relationship between neurotransmission-related amino acid blood concentrations and neuropsychological performance following acute exercise
PubMed ID: 35227132
Study links acute tyrosine increases after intense exercise to better cognitive performance — supports reduction of mental fatigue under acute stress.
- Cognitive and Mood Effects of a Nutrient Enriched Breakfast Bar in Healthy Adults: A Randomised, Double-Blind, Placebo-Controlled, Parallel Groups Study
PubMed ID: 29215606
Nutrient‑enriched bar (contains L‑tyrosine) reduced subjective mental fatigue acutely (multi‑ingredient trial).
- Branched-chain amino acids enhance the cognitive recovery of patients with severe traumatic brain injury
PubMed ID: 16181934
Raised tyrosine associated with faster recovery of cognitive function after severe injury — consistent with reduced mental fatigue/greater cognitive endurance.
Mental clarity (19)
- Food for creativity: tyrosine promotes deep thinking
PubMed ID: 25257259
Direct evidence of improved convergent (deep/problem‑solving) thinking indicates clearer, more effective cognition.
- The relationship between neurotransmission-related amino acid blood concentrations and neuropsychological performance following acute exercise
PubMed ID: 35227132
Tyrosine increases after intense exercise correlated with improvements on cognitive tests (supports clarity/processing).
- Cognitive and Mood Effects of a Nutrient Enriched Breakfast Bar in Healthy Adults: A Randomised, Double-Blind, Placebo-Controlled, Parallel Groups Study
PubMed ID: 29215606
Participants reported reduced mental fatigue and improved cognitive measures after the nutrient bar containing L‑tyrosine—supports improved clarity though multi‑ingredient.
- Branched-chain amino acids enhance the cognitive recovery of patients with severe traumatic brain injury
PubMed ID: 16181934
Improved cognitive recovery with increased tyrosine after severe brain injury supports clearer thinking/mental clarity with higher tyrosine availability.
- Effects of tyrosine, phentermine, caffeine D-amphetamine, and placebo on cognitive and motor performance deficits during sleep deprivation
PubMed ID: 12887140
Improved logical reasoning and running memory under sleep deprivation indicates clearer thinking in that stress context.
- Effect of Supplementation of a Whey Peptide Rich in Tryptophan-Tyrosine-Related Peptides on Cognitive Performance in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Study
PubMed ID: 30011836
Improvements in attention/verbal fluency in fatigued subjects indicate clearer cognitive functioning with Tyr‑containing peptides.
- Effects of serotonin depletion and dopamine depletion on bimodal divided attention
PubMed ID: 30295116
Divided attention and reaction‑time effects after precursor manipulation provide moderate evidence for effects on clarity of processing.
- Cerebrospinal and plasma amino acid concentrations after administration of i.v. glycyl-glutamine and glycyl-tyrosine containing amino acid solutions in humans
PubMed ID: 8865110
Demonstrated CSF increase in tyrosine — supports plausibility that supplementation could affect clarity via neurotransmitter synthesis.
- The effects of L-dihydroxyphenylalanine on alertness and mood in alpha-methyl-para-tyrosine-treated healthy humans. Further evidence for the role of catecholamines in arousal and anxiety
PubMed ID: 8526970
Reversal of AMPT-induced sleepiness/negative mood by L‑dopa implies catecholamine support helps clarity of thought/alert cognition.
- Impact of L-theanine and L-tyrosine on markers of stress and cognitive performance in response to a virtual reality based active shooter training drill
PubMed ID: 38975711
Fewer missed Stroop responses under stress indicate clearer, more accurate cognitive processing with L‑tyrosine.
- Sleep deprivation and impaired cognition. Possible role of brain catecholamines
PubMed ID: 1356024
AMPT and sleep deprivation caused marked cognitive impairment → indirect evidence catecholamine availability supports mental clarity.
- Effects of catecholamine depletion on alertness and mood in rested and sleep deprived normal volunteers
PubMed ID: 8099791
Catecholamine depletion increased sleepiness/impairment, supporting the idea that tyrosine availability helps maintain clear cognition (indirect).
- Antidopaminergic effects of dietary tyrosine depletion in healthy subjects and patients with manic illness
PubMed ID: 11581118
Dietary tyrosine manipulation influenced dopamine-related cognition/mood; supports an indirect role in mental clarity.
- Reward processing after catecholamine depletion in unmedicated, remitted subjects with major depressive disorder
PubMed ID: 19393989
Catechol depletion produced cognitive/affective deficits — inverse evidence supports catechol precursor role in clarity.
- Dose-Dependent Effects of Oral Tyrosine Administration on Plasma Tyrosine Levels and Cognition in Aging
PubMed ID: 29168741
Working memory/complex N‑back performance maps to mental clarity; study directly measured this domain but found impairment at higher doses in older adults.
- Dopamine depletion effects on cognitive flexibility as modulated by tDCS of the dlPFC
PubMed ID: 31494070
Evidence that lowered tyrosine impairs cognitive performance (reaction time/task switching), implying tyrosine supports clarity.
- Tyrosine negatively affects flexible-like behaviour under cognitively demanding conditions
PubMed ID: 31521870
Directly assessed cognitive flexibility (component of mental adaptability/clarity) under high load — found worsened flexibility, so highly relevant evidence but showing impairment rather than improvement.
- Increased dopamine availability magnifies nicotine effects on cognitive control: A pilot study
PubMed ID: 32133910
Improved working memory accuracy and altered cognitive control indicate clearer short-term cognitive processing acutely.
- Effects of ingesting a pre-workout dietary supplement with and without synephrine for 8Â weeks on training adaptations in resistance-trained males
PubMed ID: 28096757
Cognitive improvements (Stroop) in product containing N‑Acetyl‑L‑Tyrosine are consistent with better clarity, though multi‑ingredient confounding exists.
Stress resilience (15)
- Decoding neural reactivation of threat during fear learning, extinction, and recall in a randomized clinical trial of L-DOPA among women with PTSD
PubMed ID: 37807886
Post‑extinction L‑DOPA reduced neural reactivation of threat and related physiological responses in women with PTSD—direct evidence of enhanced stress/extinction resilience.
- Effects of Dopaminergic Therapy with Levodopa (L-DOPA) on Fear and Anxiety-Related Circuits and Symptoms in Patients with Depression and Higher Inflammation
PubMed ID: 41478464
L‑DOPA increased amygdala–vmPFC connectivity and decreased state anxiety/PTSD symptoms in inflamed patients—relevant to stress resilience.
- Impact of L-theanine and L-tyrosine on markers of stress and cognitive performance in response to a virtual reality based active shooter training drill
PubMed ID: 38975711
Under a simulated stress drill, L‑tyrosine improved cognitive performance (fewer missed responses) despite no change in stress biomarkers.
- Sleep deprivation and impaired cognition. Possible role of brain catecholamines
PubMed ID: 1356024
AMPT + sleep deprivation caused severe cognitive impairment → strong indirect evidence that catecholamine availability (tyrosine→catecholamines) supports cognitive resilience under stress.
- Antidopaminergic effects of dietary tyrosine depletion in healthy subjects and patients with manic illness
PubMed ID: 11581118
Dietary tyrosine manipulation changed dopamine-related responses to stimulants and mood, consistent with a role in stress/vulnerability of dopaminergic function.
- Psychoneuroendocrine effects of combined thyroxine and triiodothyronine versus tyrosine during prolonged Antarctic residence
PubMed ID: 18274206
12 g/day tyrosine in Antarctic residents improved winter mood and altered thyroid markers under seasonal stress (placebo-controlled).
- Reward processing after catecholamine depletion in unmedicated, remitted subjects with major depressive disorder
PubMed ID: 19393989
AMPT-caused catecholamine depletion increased depressive symptoms and slowed RT — strong inverse evidence that catechol support aids resilience under stress.
- Reduction in total plasma ghrelin levels following catecholamine depletion: relation to bulimic and depressive symptoms
PubMed ID: 23333252
AMPT (tyrosine hydroxylase inhibition) produced neurochemical/mood changes linking catecholamine availability to mood—relevant to stress responses; supports mechanistic plausibility for tyrosine improving stress resilience.
- Fear expression is suppressed by tyrosine administration
PubMed ID: 31690824
Direct human trial: single 2 g oral L‑tyrosine abolished conditioned SCR fear response (strong, specific evidence for reduced physiological fear/stress expression).
- Supplementation with whey peptide rich in β-lactolin improves trait anxiety and subjective stress in healthy adults: a randomized, double-blind, placebo-controlled study
PubMed ID: 39379481
Randomized trial: tyrosine‑containing whey peptide reduced trait anxiety and perceived stress — directly relevant.
- Cerebrospinal and plasma amino acid concentrations after administration of i.v. glycyl-glutamine and glycyl-tyrosine containing amino acid solutions in humans
PubMed ID: 8865110
Shows CNS uptake of tyrosine — biological plausibility that supplementation could support stress resilience via catecholamine synthesis.
- Effects of tyrosine, phentermine, caffeine D-amphetamine, and placebo on cognitive and motor performance deficits during sleep deprivation
PubMed ID: 12887140
Improved cognitive performance during sleep deprivation (an acute stressor) suggests better resilience to cognitive stress.
- Branched-chain amino acids enhance the cognitive recovery of patients with severe traumatic brain injury
PubMed ID: 16181934
Improved cognitive recovery with raised tyrosine after severe injury suggests greater resilience of cognitive processes with higher tyrosine availability.
- The relationship between neurotransmission-related amino acid blood concentrations and neuropsychological performance following acute exercise
PubMed ID: 35227132
Acute exercise increased tyrosine and explained variance in cognitive test improvements—supports tyrosine improving cognition under acute physiological stress.
- Effects of Five Amino Acids (Serine, Alanine, Glutamate, Aspartate, and Tyrosine) on Mental Health in Healthy Office Workers: A Randomized, Double-Blind, Placebo-Controlled Exploratory Trial
PubMed ID: 35684157
Multi‑AA (including tyrosine) improved recovery/motivation after sustained mental work — suggests improved resilience to mental stress, though not tyrosine‑specific.
Memory (15)
- Baseline-dependent effect of dopamine's precursor L-tyrosine on working memory gating but not updating
PubMed ID: 32133585
Direct evidence: single‑dose 2 g L‑tyrosine modulated working‑memory gate opening (reduced between‑subject variance and baseline‑dependent benefit), the clearest direct cognitive endpoint in the dataset.
- Cognitive and Mood Effects of a Nutrient Enriched Breakfast Bar in Healthy Adults: A Randomised, Double-Blind, Placebo-Controlled, Parallel Groups Study
PubMed ID: 29215606
Working memory tasks (Corsi span, serial subtractions) improved acutely after the nutrient bar that included L‑tyrosine (multi‑ingredient confound).
- Branched-chain amino acids enhance the cognitive recovery of patients with severe traumatic brain injury
PubMed ID: 16181934
Raised tyrosine associated with improved cognitive recovery — implies working memory gains in clinical population.
- Effects of tyrosine, phentermine, caffeine D-amphetamine, and placebo on cognitive and motor performance deficits during sleep deprivation
PubMed ID: 12887140
Running memory performance improved in the sleep‑deprived cohort, a direct working‑memory measure.
- Preliminary evidence for an association between intake of high-fat high-sugar diet, variations in peripheral dopamine precursor availability and dopamine-dependent cognition in humans
PubMed ID: 33270945
Direct evidence: dopamine‑precursor depletion impaired working memory in the low HFS diet group—strongest direct link to working memory.
- Cerebrospinal and plasma amino acid concentrations after administration of i.v. glycyl-glutamine and glycyl-tyrosine containing amino acid solutions in humans
PubMed ID: 8865110
Shows tyrosine reaches CSF — provides mechanistic plausibility for working memory effects via catecholaminergic pathways.
- Effects of whey-derived lactopeptide β-lactolin on cognitive performance in mild cognitive impairment: a randomized, double-blind, placebo-controlled trial
PubMed ID: 39560119
In MCI, β‑lactolin (tyrosine‑containing peptide) improved delayed recall and some MoCA metrics — direct WM relevance.
- Different effects of dopaminergic and anticholinergic therapies on cognitive and motor function in Parkinson's disease. A follow-up study of untreated patients
PubMed ID: 1486457
Study reported dopaminergic drugs improved working‑memory and sequencing tasks directly (stronger indirect evidence linking dopamine to working memory).
- The effects of L-dihydroxyphenylalanine on alertness and mood in alpha-methyl-para-tyrosine-treated healthy humans. Further evidence for the role of catecholamines in arousal and anxiety
PubMed ID: 8526970
Catecholamine depletion produced cognitive/affective declines reversed by L‑dopa — implies dopaminergic tone supports working memory functions (mechanistic human data).
- Sleep deprivation and impaired cognition. Possible role of brain catecholamines
PubMed ID: 1356024
AMPT ± sleep deprivation caused cognitive deficits → indirect evidence catecholamines (tyrosine derivatives) support working memory, especially under stress.
- Antidopaminergic effects of dietary tyrosine depletion in healthy subjects and patients with manic illness
PubMed ID: 11581118
Dietary tyrosine removal lowered dopamine neurotransmission and reduced psychostimulant effects; supports that tyrosine availability impacts dopamine-dependent working memory.
- Reward processing after catecholamine depletion in unmedicated, remitted subjects with major depressive disorder
PubMed ID: 19393989
AMPT impaired reward RT and mood; catechol depletion effects imply working memory may be catechol-sensitive (inverse evidence).
- Dose-Dependent Effects of Oral Tyrosine Administration on Plasma Tyrosine Levels and Cognition in Aging
PubMed ID: 29168741
Directly assessed (N‑back). Very relevant mapping, though results showed impairment at higher doses in older adults (not improvement).
- Increased dopamine availability magnifies nicotine effects on cognitive control: A pilot study
PubMed ID: 32133910
Direct finding: single-dose L-tyrosine improved n-back working memory accuracy (~4–5% absolute improvement).
- The relationship between neurotransmission-related amino acid blood concentrations and neuropsychological performance following acute exercise
PubMed ID: 35227132
Digit Span improvements reported in association with exercise-induced tyrosine rise (direct working memory measure).
Mood balance (13)
- Antidopaminergic effects of dietary tyrosine depletion in healthy subjects and patients with manic illness
PubMed ID: 11581118
Removing dietary tyrosine lowered dopamine measures and reduced mania/psychostimulant effects, indicating a clear link to mood and dopaminergic state.
- Psychoneuroendocrine effects of combined thyroxine and triiodothyronine versus tyrosine during prolonged Antarctic residence
PubMed ID: 18274206
Randomized, placebo-controlled trial: 12 g/day tyrosine significantly improved mood in Antarctic winter residents.
- Reward processing after catecholamine depletion in unmedicated, remitted subjects with major depressive disorder
PubMed ID: 19393989
AMPT increased depressive symptoms in remitted MDD — strong inverse evidence that boosting catechol synthesis (e.g., tyrosine) may support mood.
- Reduction in total plasma ghrelin levels following catecholamine depletion: relation to bulimic and depressive symptoms
PubMed ID: 23333252
Directly relevant: AMPT‑induced catecholamine depletion correlated with depressive symptoms, showing catecholamine availability (downstream of tyrosine) influences mood—strong indirect support for tyrosine's potential.
- Effects of Five Amino Acids (Serine, Alanine, Glutamate, Aspartate, and Tyrosine) on Mental Health in Healthy Office Workers: A Randomized, Double-Blind, Placebo-Controlled Exploratory Trial
PubMed ID: 35684157
Trial found significant improvement in motivation (psychological/mood‑related VAS) after 4 weeks of multi‑AA supplement that included tyrosine.
- Neurotransmitter-precursor-supplement intervention for detoxified heroin addicts
PubMed ID: 22684569
Randomized trial of a neurotransmitter‑precursor supplement (contained tyrosine) showed significant improvements in multiple POMS mood subscales vs placebo; attribution to tyrosine alone is confounded.
- Baseline serum amino acid levels predict treatment response to augmentation with N-acetylcysteine (NAC) in a bipolar disorder randomised trial
PubMed ID: 34438354
Human trial found baseline tyrosine among amino acids predicting antidepressant response — fairly direct link to mood biology.
- Supplementation with whey peptide rich in β-lactolin improves trait anxiety and subjective stress in healthy adults: a randomized, double-blind, placebo-controlled study
PubMed ID: 39379481
Randomized human study: tyrosine‑containing whey peptide reduced trait anxiety and perceived stress (mood benefit).
- The effects of L-dihydroxyphenylalanine on alertness and mood in alpha-methyl-para-tyrosine-treated healthy humans. Further evidence for the role of catecholamines in arousal and anxiety
PubMed ID: 8526970
AMPT (catecholamine synthesis blocker) increased negative mood; L‑dopa reversed these effects — direct human evidence linking catecholamine synthesis to mood regulation.
- Pramipexole and pergolide in the treatment of depression in Parkinson's disease: a national multicentre prospective randomized study
PubMed ID: 12823492
Pramipexole produced significant improvement in MADRS (depression) in PD — direct dopaminergic mood benefit.
- Quality of life in early Parkinson's disease treated with levodopa/carbidopa/entacapone
PubMed ID: 18846551
Adding entacapone to levodopa/carbidopa produced small but significant improvements in nonmotor domains including depression-related QoL metrics.
- Effects of Dopaminergic Therapy with Levodopa (L-DOPA) on Fear and Anxiety-Related Circuits and Symptoms in Patients with Depression and Higher Inflammation
PubMed ID: 41478464
L‑DOPA reduced anxiety and some PTSD symptoms and altered limbic‑prefrontal connectivity—direct mood‑relevant effects.
- Effects of catecholamine depletion on alertness and mood in rested and sleep deprived normal volunteers
PubMed ID: 8099791
AMPT produced marked negative mood when combined with sleep deprivation, indicating catecholamine synthesis (downstream of tyrosine) influences mood (mechanistic, indirect).
Motivation & confidence (8)
- Effects of Five Amino Acids (Serine, Alanine, Glutamate, Aspartate, and Tyrosine) on Mental Health in Healthy Office Workers: A Randomized, Double-Blind, Placebo-Controlled Exploratory Trial
PubMed ID: 35684157
Primary reported effect: motivation VAS improved significantly after 4 weeks of the amino‑acid formulation that included L‑tyrosine.
- Acute phenylalanine/tyrosine depletion reduces motivation to smoke cigarettes across stages of addiction
PubMed ID: 21775977
APTD (tyrosine/phenylalanine depletion) reduced smokers' willingness to work for nicotine, implying preserved tyrosine availability supports motivated effort; strong behavioral signal.
- Serotonin and dopamine differentially affect appetitive and aversive general Pavlovian-to-instrumental transfer
PubMed ID: 25034118
Lowering dopamine precursors reduced the motivational influence of appetitive cues (appetitive PIT), directly implicating Tyr/Phe in motivation.
- The effects of L-dihydroxyphenylalanine on alertness and mood in alpha-methyl-para-tyrosine-treated healthy humans. Further evidence for the role of catecholamines in arousal and anxiety
PubMed ID: 8526970
Catecholamine blockade decreased arousal/mood that was reversed by L‑dopa — supports role of dopamine/noradrenaline in motivation.
- Dopamine modulates reward system activity during subconscious processing of sexual stimuli
PubMed ID: 22395731
Levodopa increased reward‑area responses to cues — supports increased motivational drive.
- Dopamine modulates reward-related vigor
PubMed ID: 23419875
L‑dopa increased how average reward influenced action vigor — strong mechanistic support for enhanced motivation.
- Antidopaminergic effects of dietary tyrosine depletion in healthy subjects and patients with manic illness
PubMed ID: 11581118
Lowered dopamine activity after tyrosine removal and altered stimulant effects suggest tyrosine availability influences motivation-related dopamine pathways.
- Reward processing after catecholamine depletion in unmedicated, remitted subjects with major depressive disorder
PubMed ID: 19393989
AMPT increased depressive symptoms (including motivational aspects) — inverse evidence that catechol precursor support may bolster motivation.
Workout performance (2)
- Dopamine modulates reward-related vigor
PubMed ID: 23419875
L‑dopa increased reward‑influenced action vigor — directly relevant to motivation for physical effort.
- Effects of ingesting a pre-workout dietary supplement with and without synephrine for 8Â weeks on training adaptations in resistance-trained males
PubMed ID: 28096757
Pre‑workout product produced larger strength gains and better cognitive test performance in exercising participants, consistent with improved workout motivation/effort; contains N‑Acetyl‑L‑Tyrosine among active ingredients.
Similar by evidence
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Products with L-Tyrosine
Search all5139 products whose verified label declares L-Tyrosine — not every bottle that mentions it in a title.
Being studied right now
Recruiting clinical trials registered on ClinicalTrials.gov. A trial in progress has no result yet — this is what the field is asking, not what it found.