Behavioral and cognitive effects of tyrosine intake in healthy human adults
Open accessAbstract
The amino acid tyrosine is the precursor to the catecholamine neurotransmitters dopamine and norepinephrine. Increasing tyrosine uptake may positively influence catecholamine-related psychological functioning. We conducted a systematic review to examine the effects of tyrosine on behavior and cognition. Fifteen studies were reviewed. All studies except one involved tyrosine loading during a single test session. In most behavioral studies, there were no significant effects of tyrosine on exercise performance. In contrast, cognitive studies employing neuropsychological measures found that tyrosine loading acutely counteracts decrements in working memory and information processing that are induced by demanding situational conditions such as extreme weather or cognitive load. The buffering effects of tyrosine on cognition may be explained by tyrosine's ability to neutralize depleted brain catecholamine levels. There is evidence that tyrosine may benefit healthy individuals exposed to demanding situational conditions. For future research we recommend moving from studying the acute effects of a single tyrosine load in small samples to studying the behavioral and cognitive effects of tyrosine in larger groups over multiple weeks.
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Claims the paper makes
13 of 59 cited sources checked · 3 supported · 0 flagged · accuracy not yet measured
- Premisecitation
The most commonly adopted hypothesis about stress-induced performance decrements holds that reduced brain catecholamine levels account for this phenomenon.
“The most commonly adopted hypothesis about stress-induced performance decrements holds that reduced brain catecholamine levels account for this phenomenon (O'Brien et al., 2007;Colzato et al., 2013).”
Quote in the paperSubstantial claim1 of 2 sources checked- cites O'Brien et al., 2007 source
- cites Colzato et al., 2013 source
The Introduction (page unavailable) describes stress as a condition that causes brain dopamine and norepinephrine depletion, supporting the proposed mechanism. The Discussion (page unavailable) also reports stress-induced working-memory and attention deficits. Neither passage establishes that reduced catecholamine levels are the most commonly adopted explanation for stress-induced performance decrements in general. (LLM, conf=0.84)
Experimental — accuracy not yet measured
- Premisecitation
The amino acid tyrosine serves as a precursor for the catecholamine neurotransmitters dopamine and norepinephrine.
“The amino acid tyrosine is the precursor to the catecholamine neurotransmitters dopamine and norepinephrine.”
- Also stated in: § 1. Introduction · plain
“Increased tyrosine intake has the potential to influence the catecholamine neurotransmitters dopamine and norepinephrine via its conversion into L-3,4-dihydroxyphenylalanine (L-DOPA), the direct precursor to dopamine, which in turn gets converted to norepinephrine (Fernstrom and Fernstrom, 2007).”
Quote in the paperSubstantial claim1 of 1 sources checked- cites Fernstrom and Fernstrom, 2007 source
- Also stated in: § 1. Introduction · plain
- Findingcitation
Three studies found superior working memory scores in the tyrosine group under physical stress from cold exposure.
“Three of these studies observed superior scores of the tyrosine group on tests of working memory under physical stress as elicited by exposure to cold temperatures (O' Brien et al., 2007;Mahoney et al., 2007;Shurtleff et al., 1994).”
Quote in the paperNot a substantial claim1 of 3 sources checked - Findingcitation
In five studies, tyrosine prevented decrements in cognitive task performance under physically or mentally tasking conditions.
“The most commonly reported effect, observed in five studies, was that tyrosine prevented decrements in cognitive task performance under physically or mentally tasking conditions.”
Quote in the paperSubstantial claim2 of 3 sources checked- cites O'Brien et al., 2007 source
- cites Mahoney et al., 2007 source
The Discussion (page not provided) reports that tyrosine reduced cold-induced working-memory decrements and identifies five stressful conditions under which the literature suggests it may be useful. It does not say that five studies found tyrosine prevented cognitive-performance decrements; it describes the human evidence as mixed and inconclusive. (LLM, conf=0.85)
Experimental — accuracy not yet measured - cites Colzato et al., 2013 source
The Discussion reports that tyrosine reversed stress-induced deficits in working-memory and attention tasks, and the Introduction reports benefits when competing task demands degraded performance. Neither passage says this was the most commonly reported effect or establishes a count of five studies. (LLM, conf=0.85)
Experimental — accuracy not yet measured
- Premisecitation
The effects of tyrosine loading on working memory and information processing speed appear similar to those of methylphenidate.
“The effects of tyrosine loading on working memory and information processing speed appear to be similar to those of methylphenidate (Linssen et al., 2014).”
Quote in the paperSubstantial claim1 of 1 sources checked- cites Linssen et al., 2014 source
The Introduction (page unavailable) says methylphenidate enhances performance on tasks measuring processing speed or working memory in healthy volunteers. It does not report effects of tyrosine loading or compare tyrosine loading with methylphenidate; the References mention tyrosine/phenylalanine depletion, which is different. (LLM, conf=0.86)
Experimental — accuracy not yet measured
- Findingcitation
Two studies found higher working memory scores in the tyrosine group on multitasking tasks.
“The other two studies observed higher scores of the tyrosine group on working memory tasks that require multitasking (Colzato et al., 2013;Thomas et al., 1999).”
Quote in the paperNot a substantial claim1 of 2 sources checked- cites Colzato et al., 2013 source
The Results (N-back task; page unavailable) report higher accuracy after tyrosine than placebo in the demanding 2-back condition. But this paper tested working-memory updating in an N-back task, not multitasking; its Introduction describes the multitask battery as part of Thomas et al. (1999). (LLM, conf=0.88)
Experimental — accuracy not yet measured - cites Thomas et al., 1999 source
- Findingreasoning
The review did not yield convincing evidence that tyrosine can acutely improve endurance exercise performance.
“Nevertheless, our review did not yield convincing evidence that tyrosine can acutely improve endurance exercise performance.”
Quote in the paperSubstantial claim - Findingnone given
All reviewed studies except one involved tyrosine loading during a single test session.
“All studies except one involved tyrosine loading during a single test session.”
Quote in the paperNot a substantial claim - Findingcitation
In the Antarctica study, plasma norepinephrine levels declined less in the tyrosine group than in the placebo group during summer.
“However, plasma norepinephrine levels declined less in the tyrosine group than in the placebo group during the summer (Palinkas et al., 2007).”
- Also stated in: § 4. Discussion · plain
“In the Antarctica study (Palinkas et al., 2007), plasma norepinephrine levels declined less in the tyrosine group than in the placebo group over the course of the Antarctic summer.”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Palinkas et al., 2007 source
- Also stated in: § 4. Discussion · plain
- Findingcitation
Tyrosine improved convergent thinking as measured by a task requiring participants to find a common associate for three seemingly unrelated words.
“In a final study, tyrosine improved convergent thinking as measured by a cognitive task which required participants to find a common associate for three seemingly unrelated words (Colzato et al., 2014).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Colzato et al., 2014
Couldn’t be matched to a paper in Crossref, so it can’t be checked.
- Findingcitation
One study observed acute tyrosine-induced elevations in prolactin during exercise.
“The other study observed acute tyrosine-induced elevations in prolactin during exercise (Strüder et al., 1998).”
- Also stated in: § 4. Discussion · plain
“One study found that tyrosine loading resulted in an increase in plasma prolactin levels during physical exercise (Strüder et al., 1998).”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Strüder et al., 1998 source
- Also stated in: § 4. Discussion · plain
- Findingcitation
Another study reported an acute tyrosine-induced increase in plasma norepinephrine levels, compared to no change in placebo.
“Another study reported an acute tyrosineinduced increase in plasma norepinephrine levels, compared to no change in the placebo condition (Kishore et al., 2013).”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Kishore et al., 2013 source
- Findingcitation
Tyrosine reduced response inhibition reaction times in one study.
“Tyrosine reduced response inhibition reaction times in one study (Tumilty et al., 2011).”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Tumilty et al., 2011 source
- Findingcitation
In the Antarctica study, plasma norepinephrine levels declined more in the tyrosine group than in the placebo group during winter.
“In the Antarctica study, plasma norepinephrine levels declined more in the tyrosine group than in the placebo group during the winter.”
- Also stated in: § 4. Discussion · plain
“However, this pattern was reversed in the Antarctic winter, when plasma norepinephrine levels declined more in the tyrosine group.”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Palinkas et al., 2007 source
- Also stated in: § 4. Discussion · plain
- Findingcitation
During the Antarctic summer, there were no significant changes in mood.
“During the summer, there were no significant changes in mood.”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Palinkas et al., 2007 source
- Findingcitation
All seven studies that measured plasma tyrosine levels found significantly elevated levels after tyrosine intake compared to placebo.
“All seven studies in which plasma tyrosine levels were measured (Strüder et al., 1998;Sutton et al., 2005;Shurtleff et al., 1994;Chinevere et al., 2002;Tumilty et al., 2011Tumilty et al., , 2014;;Watson et al., 2012) found these levels to be significantly elevated after tyrosine intake compared to placebo.”
Quote in the paperNot a substantial claim0 of 3 sources checked - Findingcitation
Tyrosine prevented heat-induced increases in reaction times in one study.
“In another study, tyrosine prevented heat-induced increases in reaction times (Kishore et al., 2013).”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Kishore et al., 2013 source
- Findingcitation
In one study, tyrosine prevented heat-induced increases in P300 latency, assessed using an auditory odd-ball paradigm.
“This study also included EEG measures and reported that the observed cognitive effect of tyrosine might be explained by preventing heat-induced increases in P300 latencies, assessed using an auditory odd-ball paradigm (Kishore et al., 2013).”
- Also stated in: § 4. Discussion · plain
“For example, tyrosine prevented heat-induced increases in P300 latency assessed using an auditory odd-ball paradigm (Kishore et al., 2013).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Kishore et al., 2013 source
- Also stated in: § 4. Discussion · plain
- Findingcitation
In the only longitudinal study, tyrosine or placebo was supplemented for two seasons to research station residents in Antarctica.
“In the only study to use a longitudinal design, tyrosine or placebo was supplemented for two seasons to research station residents in Antarctica (Palinkas et al., 2007).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Palinkas et al., 2007 source
- Premisecitation
Under typical physiological conditions, tyrosine hydroxylase, the enzyme that converts tyrosine to L-DOPA, is about 75% saturated with tyrosine.
“Tyrosine hydroxylase, the enzyme involved in the conversion from tyrosine to L-DOPA, is about 75% saturated with tyrosine under typical physiological conditions (Carlsson and Lindqvist, 1978).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Carlsson and Lindqvist, 1978 source
- Premisecitation
Reduced brain catecholamine levels appear to make mood more vulnerable to the negative effects of low light exposure.
“Moreover, reduced brain catecholamine levels seem to make mood more vulnerable to the negative effects of low light exposure (Cawley et al., 2013).”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Cawley et al., 2013 source
- Interpretationreasoning
Because the other enzymes in catecholamine synthesis have low saturation rates, raising local tyrosine levels has a modest but significant potential to increase brain catecholamine synthesis.
“As the other enzymes involved in catecholamine synthesis have low saturation rates, there is a modest but significant potential to increase brain catecholamine synthesis by increasing local tyrosine levels.”
Quote in the paperSubstantial claim - Premisecitation
The P300 response is linked with alterations in the firing of norepinephrine neurons in the locus coeruleus.
“This idea is consistent with research linking the P300 response with alterations in the firing of norepinephrine neurons in the locus coeruleus (Nieuwenhuis et al., 2005).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Nieuwenhuis et al., 2005 source
- Interpretationreasoning
Tyrosine loading may not be sufficient to counteract exercise-induced physical fatigue.
“This suggests that tyrosine loading may not be sufficient to counteract exercise-induced physical fatigue.”
Quote in the paperSubstantial claim - Interpretationcitation
The mixed results on endurance exercise performance suggest that tyrosine loading may not be very useful for that purpose.
“The mixed results on endurance exercise performance suggest that tyrosine loading may not be very useful in this context: only one out of six similarly designed studies found tyrosine to enhance performance relative to placebo (Tumilty et al., 2011).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Tumilty et al., 2011 source
- Interpretationreasoning
Tyrosine could aid workers in demanding office jobs or military soldiers on a mission.
“Tyrosine could thus aid workers in demanding office jobs or military soldiers on a mission.”
Quote in the paperSubstantial claim - Study design and conductown data
All reviewed studies used randomized, double-blind, placebo-controlled designs.
“All studies were placebo-controlled and conducted under double-blind conditions.”
- Also stated in: § 4. Discussion · plain
“The studies included in this systematic review used randomized double-blind, placebo-controlled designs (see Table 1).”
Quote in the paperSubstantial claim - Also stated in: § 4. Discussion · plain
- Interpretationreasoning
Tyrosine is more likely to influence mood during the winter than during the summer.
“This can help explain why tyrosine is more likely to influence mood during the winter than during the summer.”
Quote in the paperSubstantial claim - Interpretationown data
Even without extreme conditions, tyrosine may improve convergent thinking.
“Moreover, even in the absence of extreme conditions, tyrosine may improve convergent thinking.”
Quote in the paperSubstantial claim - Interpretationreasoning
Tyrosine could help athletes in sports that demand cognitive and psychomotor performance under difficult conditions, such as biathlon.
“Moreover, tyrosine loading had consistent effects on working memory and information processing, which suggests that tyrosine could help athletes in sports that demand cognitive and psychomotor performance under difficult conditions, such as biathlon.”
Quote in the paperSubstantial claim - Interpretationreasoning
For athletes whose sport requires fine motor skills and substantial cognitive effort, tyrosine has greater potential as an effective performance aid.
“For athletes whose sport requires fine motor skills and a lot of cognitive effort to perform well, tyrosine has greater potential as an effective performance aid.”
Quote in the paperSubstantial claim - Interpretationreasoning
When a situation imposes heavy cognitive loads or harsh environmental conditions, tyrosine is able to prevent or reverse the cognitive performance decrements induced by these conditions.
“When a situation imposes heavy cognitive loads or harsh environmental conditions upon people, tyrosine is able to prevent or reverse the cognitive performance decrements induced by these conditions.”
Quote in the paperSubstantial claim - Interpretationreasoning
The quality of the reviewed studies was better than that of the case studies and mostly uncontrolled studies previously described by Young (1996).
“This suggests that their quality was better than that of the case studies and mostly uncontrolled studies previously described by Young (1996).”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Young, 1996 source
- Premisecitation
The release of prolactin from the anterior pituitary is inhibited by dopamine in the brain.
“This was unexpected because the release of prolactin from the anterior pituitary is inhibited, rather than stimulated, by dopamine in the brain (Strüder et al., 1998;Harmer et al., 2001).”
Quote in the paperSubstantial claim0 of 2 sources checked - Interpretationreasoning
Increased tyrosine intake can have beneficial effects on psychological functioning.
“We conclude that increased tyrosine intake can have beneficial effects on psychological functioning.”
Quote in the paperSubstantial claim - Study design and conductnone given
The total number of selected studies was limited.
“For instance, the total number of selected studies was limited.”
Quote in the paperSubstantial claim - Study design and conductcitation
Some studies used a placebo rich in carbohydrates, such as orange juice, which may have inadvertently affected brain uptake of tyrosine.
“Furthermore, some studies used a placebo that was rich in carbohydrates (e.g., orange juice), which may have inadvertently affected brain uptake of tyrosine (Wurtman et al., 2003).”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Wurtman et al., 2003 source
- Premisecitation
One additional longitudinal study not included in the review because of its case study design without a control condition found that tyrosine supplementation, ranging from a few months to several years, improved strength and motor control in children and adolescents with nemaline myopathy.
“Nevertheless, one additional longitudinal study not included in our review due to its case study design without a control condition found that tyrosine supplementation, ranging from a few months to several years, was able to improve strength and motor control in children and adolescents with nemaline myopathy (Ryan et al., 2008).”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Ryan et al., 2008 source
- May combine two claims. 16
- Classified as probably not a substantial claim. 12
- The quote only partly states this claim. 1
May combine two claims.
PremisecitationTyrosine depletion experiments suggest that acute reductions in brain catecholamine levels lead people to behave in a less motivated way or to develop cognitive impairments.
“In line with this, tyrosine depletion experiments, in which participants consume an amino acid mixture devoid of tyrosine and its precursor, phenylalanine, suggest that acute reductions in brain catecholamine levels lead people to behave in a less motivated way (McLean et al., 2004;Roiser et al., 2005;Cawley et al., 2013) or develop cognitive impairments (Harmer et al., 2001).”
Quote in the paperSubstantial claim1 of 3 sources checked- cites McLean et al., 2004 source
- cites Roiser et al., 2005 source
The Discussion reports that acute phenylalanine and tyrosine depletion made patients recovered from depression bet less, possibly because they were less sensitive to reward. This supports the suggested motivation-related effect, but the study tested that specific patient group rather than people generally. The cognitive-impairment clause is attributed to Harmer et al., not Roiser et al. (LLM, conf=0.82)
Experimental — accuracy not yet measured - cites Harmer et al., 2001 source
May combine two claims.
PremisecitationAnimal studies suggest that short days increase dopamine turnover in the pituitary and suppress tyrosine hydroxylase expression in the prefrontal cortex.
“In line with this hypothesis, animal studies suggest that short days increase dopamine turnover in the pituitary (Steger et al., 1995) and suppress tyrosine hydroxylase expression in the prefrontal cortex (Sorg et al., 2011).”
Quote in the paperSubstantial claim1 of 2 sources checkedClassified as probably not a substantial claim.
PremisecitationThe catecholamine depletion hypothesis proposes that tyrosine can exert beneficial effects when brain catecholamine levels are low and there is more room for tyrosine to be converted into L-DOPA, which then becomes dopamine and norepinephrine.
“As stated in the Introduction, the catecholamine depletion hypothesis proposes that tyrosine can exert beneficial effects when brain catecholamine levels are low and there is more room for tyrosine to be converted into L-DOPA, which then gets converted into dopamine and norepinephrine (Fernstrom and Fernstrom, 2007;O'Brien et al., 2007;Colzato et al., 2013).”
Quote in the paperSubstantial claim2 of 3 sources checked- cites Fernstrom and Fernstrom, 2007 source
Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.
Experimental — accuracy not yet measured - cites O'Brien et al., 2007 source
- cites Colzato et al., 2013 source
Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.
Experimental — accuracy not yet measured
May combine two claims.
PremisecitationThe side effects of tyrosine appear milder and less frequent than those of methylphenidate, though toxicity data on long-term use are lacking.
“At the same time, the side effects of tyrosine appear to be milder and less frequent (Young, 1996) than those of methylphenidate (Linssen et al., 2014), though toxicity data on their long-term use are lacking.”
Quote in the paperSubstantial claim1 of 2 sources checked- cites Young, 1996 source
- cites Linssen et al., 2014 source
The Results (sections 3.3 and 3.4; page unavailable) report increased tension, heart rate, and blood pressure after methylphenidate. Our copy does not compare its side effects with tyrosine’s or address long-term toxicity, so it supports only the methylphenidate-effects portion of the claim. (LLM, conf=0.82)
Experimental — accuracy not yet measured
May combine two claims.
InterpretationcitationAlterations in locus coeruleus firing could be mitigated by increases in norepinephrine synthesis caused by tyrosine loading, thus restoring the locus coeruleus signal represented in the P300 response.
“Hence, alterations in locus coeruleus firing could be mitigated by the increases in norepinephrine synthesis caused by tyrosine loading (Devilbiss and Berridge, 2006;Bari and Aston-Jones, 2013), thus restoring the Locus coeruleus signal that is represented in the P300 response.”
Quote in the paperSubstantial claim1 of 2 sources checked- cites Devilbiss and Berridge, 2006 source
- cites Bari and Aston-Jones, 2013 source
The Introduction describes norepinephrine’s role in neural responses, and the Discussion addresses atomoxetine’s effects on locus coeruleus firing. Neither establishes that tyrosine loading increases norepinephrine synthesis, mitigates altered firing, or restores a locus coeruleus signal in the P300 response (searched: tyrosine loading, norepinephrine synthesis, P300). (LLM, conf=0.73)
Experimental — accuracy not yet measured
Probably not a substantial claim: may not pass S3 (load-bearing).
Findingown dataThe systematic review identified 15 studies that met the inclusion criteria.
“Fifteen studies were reviewed.”
- Also stated in: § 3. Results · plain
“Characteristics and main outcomes of the 15 reviewed studies are presented in Table 1.”
Quote in the paperNot a substantial claim- Also stated in: § 3. Results · plain
May combine two claims.
FindingcitationThe Antarctica study reported lower serum thyroid-stimulating hormone and higher plasma free triiodothyronine levels as a result of tyrosine supplementation during winter, with no effects during summer.
“The Antarctica study reported lower serum thyroid-stimulating hormone and higher plasma free triiodothyronine levels as a result of tyrosine supplementation during the winter season, with no effects during the summer (Palinkas et al., 2007).”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Palinkas et al., 2007 source
May combine two claims.
FindingcitationAmong six studies of endurance exercise performance in physically trained young men, five found no significant difference between tyrosine and placebo, while one found tyrosine enhanced performance.
“While one study found tyrosine to enhance endurance exercise performance (Tumilty et al., 2011), five studies found no significant differences between tyrosine and the placebo (Strüder et al., 1998;Sutton et al., 2005;Chinevere et al., 2002;Tumilty et al., 2014;Watson et al., 2012).”
- Also stated in: § Abstract · plain
“In most behavioral studies, there were no significant effects of tyrosine on exercise performance.”
Quote in the paperNot a substantial claim0 of 3 sources checked- Also stated in: § Abstract · plain
The quote only partly states this claim.
Findingown dataOnly one reviewed study involved repeated tyrosine dosing over multiple days or daily supplementation over multiple weeks.
“Our literature search yielded only one study which involved repeated tyrosine dosing over multiple days (Palinkas et al., 2007).”
- Also stated in: § 4. Discussion · plain
“Finally, only one study used daily tyrosine supplementation over the course of multiple weeks rather than acute loading on a single test day.”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Palinkas et al., 2007 source
- Also stated in: § 4. Discussion · plain
May combine two claims.
FindingcitationOver the Antarctic winter, tyrosine increased global mood scores from baseline by 47%, while placebo decreased them by 136%.
“Over the course of the Antarctic winter, tyrosine increased global mood scores from baseline by 47%, whereas in the placebo condition global mood scores decreased by 136%.”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Palinkas et al., 2007 source
May combine two claims.
Findingnone givenBehavioral effects of tyrosine have not been consistently supported, but low sample sizes limit the conclusions of the respective studies.
“Behavioral effects have not been consistently supported, but low sample sizes limit the conclusions of the respective studies.”
Quote in the paperSubstantial claimClassified as probably not a substantial claim.
PremisecitationSelective increases in tyrosine intake may benefit aspects of human behavior and cognition that are under catecholaminergic control.
“In short, selective increases in the intake of tyrosine may benefit those aspects of human behavior and cognition that are under the catecholaminergic control (Young, 1996).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Young, 1996 source
Classified as probably not a substantial claim.
InterpretationreasoningPositive effects of increased tyrosine intake in demanding situations could be explained by replenishment of brain catecholamines.
“Consequently, positive effects of increased tyrosine intake in demanding situations could be explained by the replenishment of brain catecholamines.”
Quote in the paperSubstantial claimProbably not a substantial claim: may not pass S3 (load-bearing).
Study design and conductown dataIn most reviewed studies, the placebo food or drink contained no protein.
“In most studies, the food or drink in the placebo condition contained no protein.”
Quote in the paperNot a substantial claimClassified as probably not a substantial claim.
PremisecitationPrevious research has shown that the detrimental effects of experimental tyrosine depletion on mood are larger in dim light than in bright light.
“As previous research has shown that the detrimental effects of experimental tyrosine depletion on mood are larger in dim light than in bright light (Cawley et al., 2013), one could hypothesize that tyrosine supplementation can exert a larger effect on mood in the absence of sunlight than in its presence, i.e. during the summer.”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Cawley et al., 2013 source
Probably not a substantial claim: may not pass S3 (load-bearing).
Study design and conductcitationOne study used an isocaloric whey protein drink as placebo, which contained some tyrosine but less than the active condition.
“In one study, the placebo was an isocaloric whey protein drink, which means it contained some tyrosine, though less than the amount of tyrosine in the active condition (Tumilty et al., 2014).”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Tumilty et al., 2014 source
Probably not a substantial claim: may not pass S3 (load-bearing).
Study design and conductnone givenAll reviewed studies except one used a within-subjects design with a counterbalanced treatment order.
“All studies except one (Palinkas et al., 2007) used a within-subjects design with a counterbalanced treatment order.”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Palinkas et al., 2007 source
Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.
InterpretationcitationBecause tyrosine can improve convergent thinking, it might help students improve their focus while studying.
“As tyrosine can improve convergent thinking (Colzato et al., 2014), in academia tyrosine might help students improve their focus while studying.”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Colzato et al., 2014
Couldn’t be matched to a paper in Crossref, so it can’t be checked.
May combine two claims.
InterpretationreasoningThe review found that tyrosine can combat decrements in working memory, slowed information processing, and worsening of mood that may be induced by physically or mentally demanding situations.
“We found that tyrosine is able to combat the decrements in working memory, slowed information processing, and worsening of mood that might be induced by physically or mentally demanding situations.”
Quote in the paperSubstantial claimClassified as probably not a substantial claim. May combine two claims.
PremisecitationDuring exercise, blood flow to skeletal muscles increases, presumably resulting in less blood flow to the brain.
“During exercise, blood flow to the skeletal muscles increases (Andersen and Saltin, 1985), presumably resulting in less blood flow to the brain.”
Quote in the paperSubstantial claim0 of 1 sources checked- cites Andersen and Saltin, 1985 source
May combine two claims.
InterpretationreasoningThe summer finding that plasma norepinephrine declined less in the tyrosine group is consistent with the catecholamine depletion hypothesis, in that tyrosine as a norepinephrine precursor should buffer a decline in norepinephrine.
“This is consistent with the catecholamine depletion hypothesis in that tyrosine, as a norepinephrine precursor, should be able to buffer a decline in norepinephrine.”
Quote in the paperNot a substantial claimClassified as probably not a substantial claim.
InterpretationreasoningGiven that tyrosine loading would be expected to increase brain dopamine levels, a subsequent decrease in plasma prolactin levels would have been expected.
“Given that tyrosine loading would be expected to increase brain dopamine levels, a subsequent decrease in plasma prolactin levels would have been expected.”
Quote in the paperSubstantial claimMay combine two claims.
InterpretationreasoningAlthough the effectiveness of loading and supplementation may differ across circumstances and applications, tyrosine can exert notable acute cognitive benefits when the situation demands increased availability of catecholamines, and may also benefit some individuals emotionally when administered over longer time periods.
“Though the effectiveness of loading and supplementation may differ across circumstances and applications, tyrosine can exert notable acute cognitive benefits when the situation demands for an increased availability of the catecholamines, and may also benefit some individuals emotionally when administered over longer time periods.”
Quote in the paperSubstantial claimMay combine two claims.
Study design and conductreasoningThe sample sizes of the reviewed studies were small to moderate, so the absence of significant effects of tyrosine on endurance exercise performance should be interpreted with caution.
“Further, as their sample sizes were small to moderate, the absence of significant effects of tyrosine on endurance exercise performance in particular should be interpreted with caution.”
Quote in the paperSubstantial claimProbably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.
PremisecitationIndividuals diagnosed with seasonal affective disorder show a marked worsening of mood in the winter, presumably as a result of the shortening of days in the fall and associated changes in the brain dopamine system.
“This might be particularly relevant to individuals diagnosed with seasonal affective disorder, who show a marked worsening of mood in the winter, presumably as a result of the shortening of days in the fall and the associated changes in the brain dopamine system (Depue et al., 1989).”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Depue et al., 1989
Couldn’t be matched to a paper in Crossref, so it can’t be checked.
May combine two claims.
InterpretationreasoningIf plasma norepinephrine levels are a biomarker of brain norepinephrine levels, then the winter finding that plasma norepinephrine declined more in the tyrosine group is inconsistent with the catecholamine depletion hypothesis.
“If plasma norepinephrine levels are a biomarker of brain norepinephrine levels, then this latter finding is inconsistent with the catecholamine depletion hypothesis.”
Quote in the paperSubstantial claim
The authors state this as an assumption.
Exercise performance is under the control of brain dopamine.
“assuming that exercise performance is under the control of brain dopamine”
The paper relies on this without support.
The P300 represents information processing, working memory, and stimulus categorization.
“The P300 is thought to represent information processing, working memory, and stimulus categorization.”
The paper relies on this without support.
The P300 latency can be interpreted as an index of the efficiency with which novel stimuli are evaluated.
“The P300 latency can be interpreted as an index of the efficiency with which novel stimuli are evaluated.”
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
Each contradiction between two passages listed here was confirmed by an independent check.
Free T3 increase is assigned to different seasons
MinorThe text says tyrosine increased free triiodothyronine during winter and had no effect during summer, but Table 1 places the increase during summer.
“The Antarctica study reported lower serum thyroid-stimulating hormone and higher plasma free triiodothyronine levels as a result of tyrosine supplementation during the winter season, with no effects during the summer (Palinkas et al., 2007).”
“-Free T3 | -Increased (during summer)”
Cites
Liberati, A., Altman, D. G., Tetzlaff, J., Mulrow, C., Gøtzsche, P. C., Ioannidis, J. P. A., Clarke, M., Devereaux, P. J., Kleijnen, J., & Moher, D. (2009) · PLoS Medicine · doi:10.1371/journal.pmed.1000100 · Cited by 28,164 · see citing works
Liberati, A., Altman, D. G., Tetzlaff, J., Mulrow, C., Gøtzsche, P. C., Ioannidis, J. P. A., Clarke, M., Devereaux, P. J., Kleijnen, J., & Moher, D. (2009) · Annals of Internal Medicine · doi:10.7326/0003-4819-151-4-200908180-00136 · Cited by 10,349 · see citing works
Decision making, the P3, and the locus coeruleus–norepinephrine system
Nieuwenhuis, S., Aston-Jones, G., & Cohen, J. D. (2005) · Psychological Bulletin · doi:10.1037/0033-2909.131.4.510 · Cited by 1,678 · see citing works
Maximal perfusion of skeletal muscle in man.
Andersen, P., & Saltin, B. (1985) · The Journal of Physiology · doi:10.1113/jphysiol.1985.sp015794 · Cited by 1,250 · see citing works
Tyrosine, Phenylalanine, and Catecholamine Synthesis and Function in the Brain2
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Student Perceptions of Methylphenidate Abuse at a Public Liberal Arts College
Babcock, Q., & Byrne, T. (2000) · Journal of American College Health · doi:10.1080/07448480009596296 · Cited by 314 · see citing works
Effects of normal meals rich in carbohydrates or proteins on plasma tryptophan and tyrosine ratios
Wurtman, R. J., Wurtman, J. J., Regan, M. M., McDermott, J. M., Tsay, R. H., & Breu, J. J. (2003) · The American Journal of Clinical Nutrition · doi:10.1093/ajcn/77.1.128 · Cited by 247 · see citing works
Whey protein supplementation during resistance training augments lean body mass
Volek, J. S., Volk, B. M., Gómez, A. L., Kunces, L. J., Kupchak, B. R., Freidenreich, D. J., Aristizabal, J. C., Saenz, C., Dunn-Lewis, C., Ballard, K. D., et al. (2013) · Journal of the American College of Nutrition · doi:10.1080/07315724.2013.793580 · Cited by 181 · see citing works
Cognitive effects of methylphenidate in healthy volunteers: a review of single dose studies
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Tyrosine depletion attenuates dopamine function in healthy volunteers
Harmer, C. J., McTavish, S. F. B., Clark, L., Goodwin, G. M., & Cowen, P. J. (2001) · Psychopharmacology · doi:10.1007/s002130000613 · Cited by 158 · see citing works
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Tyrosine reverses a cold-induced working memory deficit in humans
Shurtleff, D., Thomas, J. R., Schrot, J., Kowalski, K., & Harford, R. (1994) · Pharmacology Biochemistry and Behavior · doi:10.1016/0091-3057(94)90299-2 · Cited by 142 · cited 3× · see citing works
“Three of these studies observed superior scores of the tyrosine group on tests of working memory under physical stress as elicited by exposure to cold temperatures (O'Brien et al., 2007; Mahoney et al., 2007; Shurtleff et al., 1994).”
BackgroundResultTyrosine supplementation mitigates working memory decrements during cold exposure
Mahoney, C. R., Castellani, J., Kramer, F. M., Young, A., & Lieberman, H. R. (2007) · Physiology & Behavior · doi:10.1016/j.physbeh.2007.05.003 · Cited by 128 · cited 3× · see citing works
“Three of these studies observed superior scores of the tyrosine group on tests of working memory under physical stress as elicited by exposure to cold temperatures (O'Brien et al., 2007; Mahoney et al., 2007; Shurtleff et al., 1994).”
BackgroundResultThe effects of tyrosine depletion in normal healthy volunteers: implications for unipolar depression
McLean, A., Rubinsztein, J. S., Robbins, T. W., & Sahakian, B. J. (2004) · Psychopharmacology · doi:10.1007/s00213-003-1586-8 · Cited by 125 · see citing works
Roiser, J. P., McLean, A., Ogilvie, A. D., Blackwell, A. D., Bamber, D. J., Goodyer, I., Jones, P. B., & Sahakian, B. J. (2005) · Neuropsychopharmacology · doi:10.1038/sj.npp.1300659 · Cited by 96 · see citing works
Working Memory Reloaded: Tyrosine Repletes Updating in the N-Back Task
Colzato, L. S., Jongkees, B. J., Sellaro, R., & Hommel, B. (2013) · Frontiers in Behavioral Neuroscience · doi:10.3389/fnbeh.2013.00200 · Cited by 89 · cited 5× · see citing works
“The remaining studies offered tyrosine in water (Strüder et al., 1998; Chinevere et al., 2002; Tumilty et al., 2011, 2014), orange juice (Colzato et al., 2013, in press), or a sugar-free fruit drink (Watson et al., 2012).”
BackgroundInfluentialBehavioral effects of dietary neurotransmitter precursors: Basic and clinical aspects
Young, S. N. (1996) · Neuroscience & Biobehavioral Reviews · doi:10.1016/0149-7634(95)00022-4 · Cited by 86 · see citing works
Bari, A., & Aston-Jones, G. (2013) · Neuropharmacology · doi:10.1016/j.neuropharm.2012.07.020 · Cited by 85 · see citing works
Tyrosine improves working memory in a multitasking environment
Thomas, J. R., Lockwood, P. A., Singh, A., & Deuster, P. A. (1999) · Pharmacology Biochemistry and Behavior · doi:10.1016/s0091-3057(99)00094-5 · Cited by 75 · cited 3× · see citing works
“The other two studies observed higher scores of the tyrosine group on working memory tasks that require multitasking (Colzato et al., 2013; Thomas et al., 1999).”
BackgroundOral tyrosine supplementation improves exercise capacity in the heat
Tumilty, L., Davison, G., Beckmann, M., & Thatcher, R. (2011) · European Journal of Applied Physiology · doi:10.1007/s00421-011-1921-4 · Cited by 68 · see citing works
Dietary l-tyrosine supplementation in nemaline myopathy
Ryan, M. M., Sy, C., Rudge, S., Ellaway, C., Ketteridge, D., Roddick, L. G., Iannaccone, S. T., Kornberg, A. J., & North, K. N. (2008) · Journal of Child Neurology · doi:10.1177/0883073807309794 · Cited by 68 · see citing works
Low-dose methylphenidate actions on tonic and phasic locus coeruleus discharge
Devilbiss, D. M., & Berridge, C. W. (2006) · The Journal of Pharmacology and Experimental Therapeutics · doi:10.1124/jpet.106.110015 · Cited by 67 · see citing works
Effects of l -tyrosine and carbohydrate ingestion on endurance exercise performance
Chinevere, T. D., Sawyer, R. D., Creer, A., Conlee, R. K., & Parcell, A. C. (2002) · Journal of Applied Physiology · doi:10.1152/japplphysiol.00625.2001 · Cited by 64 · see citing works
Cawley, E., Park, S., aan het Rot, M., Sancton, K., Benkelfat, C., Young, S., Boivin, D., & Leyton, M. (2013) · Journal of Psychiatry & Neuroscience · doi:10.1503/jpn.120181 · Cited by 61 · see citing works
Self-citationDietary tyrosine benefits cognitive and psychomotor performance during body cooling
O'Brien, C., Mahoney, C., Tharion, W. J., Sils, I. V., & Castellani, J. W. (2007) · Physiology & Behavior · doi:10.1016/j.physbeh.2006.09.027 · Cited by 58 · see citing works
Eating to stop: Tyrosine supplementation enhances inhibitory control but not response execution
Colzato, L. S., Jongkees, B. J., Sellaro, R., van den Wildenberg, W. P. M., & Hommel, B. (2014) · Neuropsychologia · doi:10.1016/j.neuropsychologia.2013.12.027 · Cited by 52 · see citing works
Ingestion of tyrosine: effects on endurance, muscle strength, and anaerobic performance
Sutton, E. E., Coll, M. R., & Deuster, P. A. (2005) · International Journal of Sport Nutrition and Exercise Metabolism · doi:10.1123/ijsnem.15.2.173 · Cited by 50 · see citing works
Energy-Yielding Macronutrients and Energy Metabolism in Sports Nutrition
Thompson, J., & Manore, M. (1999) · Cited by 46 · see citing works
Food for creativity: tyrosine promotes deep thinking
Colzato, L. S., de Haan, A. M., & Hommel, B. (2014) · Psychological Research · doi:10.1007/s00426-014-0610-4 · Cited by 44 · see citing works
Watson, P., Enever, S., Page, A., Stockwell, J., & Maughan, R. J. (2012) · International Journal of Sport Nutrition and Exercise Metabolism · doi:10.1123/ijsnem.22.5.363 · Cited by 40 · see citing works
Failure of oral tyrosine supplementation to improve exercise performance in the heat
TUMILTY, L., DAVISON, G., BECKMANN, M., & THATCHER, R. (2014) · Medicine & Science in Sports & Exercise · doi:10.1249/mss.0000000000000243 · Cited by 30 · see citing works
Photoperiodic suppression of drug reinstatement
Sorg, B. A., Stark, G., Sergeeva, A., & Jansen, H. T. (2011) · Neuroscience · doi:10.1016/j.neuroscience.2010.12.022 · Cited by 25 · see citing works
Kishore, K., Ray, K., Anand, J. P., Thakur, L., Kumar, S., & Panjwani, U. (2013) · Brain and Cognition · doi:10.1016/j.bandc.2013.09.005 · Cited by 19 · cited 7× · see citing works
“For example, tyrosine prevented heat-induced increases in P300 latency assessed using an auditory odd-ball paradigm (Kishore et al., 2013).”
BackgroundMethodInfluentialPalinkas, L. A., Reedy, K. R., Smith, M., Anghel, M., Steel, G. D., Reeves, D., Shurtleff, D., Case, H. S., Do, N. V., & Reed, H. L. (2007) · International Journal of Circumpolar Health · doi:10.3402/ijch.v66i5.18312 · Cited by 16 · see citing works
Steger, R. W., Juszczak, M., Fadden, C., & Bartke, A. (1995) · Endocrinology · doi:10.1210/endo.136.7.7789325 · Cited by 15 · cited 1× · see citing works
“In linewith this hypothesis, animal studies suggest that short days increase dopamine turnover in the pituitary (Steger et al., 1995) and suppress tyrosine hydroxylase expression in the prefrontal cortex (Sorg et al., 2011).”
BackgroundSteger, R. W. (1995) · Endocrinology · doi:10.1210/en.136.7.3000 · Cited by 3 · see citing works
Flagged first, then by citations
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Boot, N. C., Baas, M., van Gaal, S., Cools, R., & Dreu, C. K. W. D. (2017) · Neuroscience & Biobehavioral Reviews · doi:10.1016/j.neubiorev.2017.04.007 · Cited by 187 · see citing works
“In addition to increasing noradrenaline levels in the brain (Hase, Jung, & aan het Rot, 2015), the amino acid L-Tyrosine acts as a precursor of dopamine (Acworth, During, & Wurtman, 1988; Hase et al., 2015).”
The impact of dietary macronutrient intake on cognitive function and the brain
Muth, A.-K., & Park, S. Q. (2021) · Clinical Nutrition · doi:10.1016/j.clnu.2021.04.043 · Cited by 197 · see citing works
Morris, N. B., Jay, O., Flouris, A. D., Casanueva, A., Gao, C., Foster, J., Havenith, G., & Nybo, L. (2020) · Environmental Health · doi:10.1186/s12940-020-00641-7 · Cited by 121 · see citing works
Blood‐based metabolic signatures in Alzheimer's disease
de Leeuw, F. A., Peeters, C. F. W., Kester, M. I., Harms, A. C., Struys, E. A., Hankemeier, T., van Vlijmen, H. W. T., van der Lee, S. J., van Duijn, C. M., Scheltens, P., et al. (2017) · Alzheimer s & Dementia Diagnosis Assessment & Disease Monitoring · doi:10.1016/j.dadm.2017.07.006 · Cited by 102 · see citing works
“Dopamine has been associated with cognitive control [38], and oral supplementation of tyrosine has been shown to improveworkingmemory and information processing during demanding situations in healthy human adults [39].”
BackgroundLongo, N., Dimmock, D., Levy, H. L., Viau, K., Bausell, H., Bilder, D. A., Burton, B. K., Gross, C., Northrup, H., Rohr, F., et al. (2018) · Genetics in Medicine · doi:10.1038/s41436-018-0403-z · Cited by 87 · see citing works
Li, Z., Hong, T., Shen, G., Gu, Y., Guo, Y., & Han, J. (2022) · Nutrients · doi:10.3390/nu14193887 · Cited by 76 · see citing works
“Leu can promote the synthesis of skeletal muscle protein and enhance human immunity [60].”
BackgroundKühn, S., Düzel, S., Colzato, L. S., Norman, K., Gallinat, J., Brandmaier, A. M., Lindenberger, U., & Widaman, K. F. (2017) · Psychological Research · doi:10.1007/s00426-017-0957-4 · Cited by 73 · see citing works
“Previous studies on the effects of a single dose of tyrosine supplements revealed short-term benefits on working memory performance and executive functions (Jongkees et al., 2015; Hase et al., 2015; van de Rest et al., 2013).”
BackgroundChen, S., & Luo, X. (2024) · Applied Food Research · doi:10.1016/j.afres.2024.100459 · Cited by 41 · see citing works
Marcolini, F., Ravaglia, A., Valenta, S. T., Bosco, G., Marconi, G., Ronchi, D. D., & Atti, A. R. (2024) · Journal of Eating Disorders · doi:10.1186/s40337-024-01006-y · Cited by 29 · see citing works
“Apparently, tyrosine supplementation affects memory-related performance, as similar studies that administered tyrosine to healthy subjects have found [61].”
Influence of nutritional tyrosine on cognition and functional connectivity in healthy old humans
Hensel, C., Becker, M., Düzel, S., Demuth, I., Norman, K., Steinhagen‐Thiessen, E., Gallinat, J., Lindenberger, U., & Kühn, S. (2019) · NeuroImage · doi:10.1016/j.neuroimage.2019.03.005 · Cited by 28 · see citing works
Regulatory mechanisms of amino acids in ferroptosis
Yao, H., Jiang, W., Liao, X., Wang, D., & Zhu, H. (2024) · Life Sciences · doi:10.1016/j.lfs.2024.122803 · Cited by 27 · see citing works
Chaudhari, K., Savjani, J., Savjani, K. T., & Shah, H. S. (2021) · Drug Development and Industrial Pharmacy · doi:10.1080/03639045.2022.2042553 · Cited by 24 · see citing works
Effects of Hypoxemia by Acute High-Altitude Exposure on Human Intestinal Flora and Metabolism
Qi, P., Lv, J., Bai, L.-H., Yan, X.-D., & Zhang, L. (2023) · Microorganisms · doi:10.3390/microorganisms11092284 · Cited by 24 · see citing works
“…the two groups, among which tyrosine was the most significantly different metabolite between the two groups. intestinal [22]. cognitive function, and it can prevent its decline associated with stress in the short term, such as cold and high-altitude stresses (that is, mild hypoxia stress) [23,24].”
BackgroundProduction of Toxins by the Gut Microbiota: The Role of Dietary Protein
Alvarenga, L., Kemp, J. A., Baptista, B. G., Ribeiro, M. M., Lima, L. S., & Mafra, D. (2024) · Current Nutrition Reports · doi:10.1007/s13668-024-00535-x · Cited by 21 · see citing works
“Tyrosine intake has behavioral and cognitive implications because catecholamines are synthesized from tyrosine [60].”
Serum tyrosine is associated with better cognition in Lewy body dementia
McCann, A., Aarsland, D., Ueland, P. M., Solvang, S.-E. H., Nordrehaug, J. E., & Giil, L. M. (2021) · Brain Research · doi:10.1016/j.brainres.2021.147481 · Cited by 18 · see citing works
Sun, Y., Zhou, L., Shan, X., et al. (2022) · LWT · doi:10.1016/j.lwt.2022.114334 · Cited by 19 · see citing works
Umeda, K., Shindo, D., Somekawa, S., Nishitani, S., Sato, W., Toyoda, S., Karakawa, S., Kawasaki, M., Mine, T., & Suzuki, K. (2022) · Nutrients · doi:10.3390/nu14112357 · Cited by 18 · see citing works
Mathar, D., Abdoust, M. E., Marrenbach, T., Tuzsus, D., & Peters, J. (2022) · PLoS Computational Biology · doi:10.1371/journal.pcbi.1010785 · Cited by 20 · see citing works
“Following previous tyrosine administration studies [6,9], participants were administered a dosage of 2 g tyrosine (supplied by The Hut.”
BackgroundMethodHypoaminoacidemia Characterizes Chronic Traumatic Brain Injury
Durham, W. J., Foreman, J., Randolph, K. M., Danesi, C. P., Spratt, H. M., Masel, B. D., Summons, J. R., Singh, C. K., Morrison, M. A., Robles, C., et al. (2016) · Journal of Neurotrauma · doi:10.1089/neu.2015.4350 · Cited by 18 · see citing works
“…TBI patients may negatively impact attention, 11,13 connectivity, 23–25 and other aspects of cognitive function, brain structure, and mood, 26–30 as tryptophan is a precursor of the neurotransmitter serotonin and phenylalanine and tyrosine are precursors for dopamine, norepinephrine, and…”
Suttiwan, P., Yuktanandana, P., & Ngamake, S. T. (2018) · Nutrients · doi:10.3390/nu10070845 · Cited by 17 · see citing works
“In healthy adults, tyrosine improved cognitive performance, especially in stressful conditions [48,49] and histidine shortened reaction time on a working memory task [50].”
BackgroundHu, C., Li, H., Wu, L., Ke, J.-Q., Yu, X.-C., Xiong, Y., & Tang, X. (2021) · Human & Experimental Toxicology · doi:10.1177/09603271211006167 · Cited by 14 · see citing works
“the precursor to the catecholamine neurotransmitters dopamine and norepinephrine, which can regulate the nervous system and accelerate metabolism.(33) The disorder of tyrosine metabolism can lead to a variety of genetic diseases, such as tyrosinemia(34) and phenylketonuria.”
BackgroundAlterations of amino acids in older adults with Alzheimer’s Disease and Vascular Dementia
Ma, X., Wang, X.-M., Tang, G.-Z., Wang, Y., Liu, X., Wang, S.-D., Peng, P., Qi, X.-H., Qin, X., Wang, C., et al. (2025) · Amino Acids · doi:10.1007/s00726-024-03442-1 · Cited by 14 · see citing works
“Increasing the intake of tyrosine can ameliorate cognitive decline (Hase et al. 2015; McCann et al. 2021).”
Phenylketonuria as an Adherence Disease
Reach, G. (2025) · Patient Preference and Adherence · doi:10.2147/ppa.s512719 · Cited by 15 · see citing works
“A meta-analysis 103 has shown that tyrosine supplementation can prevent declines in cognitive task performance, particularly under physically or mentally demanding conditions.”
Psychophysiology of sport, exercise, and performance: Past, present, and future.
Cooke, A., & Ring, C. (2019) · Sport Exercise and Performance Psychology · doi:10.1037/spy0000156 · Cited by 13 · see citing works
A review on finger millet properties, processing, health benefits, and applications
Ashik Somarajan, K., & Morya, S. (2022) · The Pharma Innovation · doi:10.22271/tpi.2022.v11.i7aq.14538 · Cited by 14 · see citing works
Ab initio study of molecular properties of l-tyrosine
Boča, R., Štofko, J., & Imrich, R. (2023) · Journal of Molecular Modeling · doi:10.1007/s00894-023-05648-8 · Cited by 11 · see citing works
Tyrosine intake and cardiovascular responses in a motivated performance situation.
Hase, A., Gorrie-Stone, T. J., & Freeman, P. B. (2018) · Sport Exercise and Performance Psychology · doi:10.1037/spy0000144 · Cited by 10 · see citing works
“As tyrosine has been found to be most effective in situations with high cognitive load or strong environmental stressors (Hase et al., 2015), it may be that stronger effects would be found in future studies that impose more cognitive load or stress on participants than the current study did,…”
BackgroundSelf-citationLi, M., Hua, S., Huang, X. H., et al. (2021) · Journal of Separation Science · doi:10.1002/jssc.202100376 · Cited by 10 · see citing works
Ren, J., Li, P., Yan, D., Li, M., Qi, J., Wang, M., Zhong, G., & Wu, M. (2021) · Journal of Microbiology and Biotechnology · doi:10.4014/jmb.2104.04038 · Cited by 10 · see citing works
Shao, P., Sha, Y., Liu, X., He, Y., Wang, F., Hu, J., Wang, J., Li, S., Chen, X., Yang, W., et al. (2024) · Animals · doi:10.3390/ani14050788 · Cited by 9 · see citing works
“An increase in the tyrosine concentration promotes the synthesis of dopamine (DA) as well as norepinephrine [34] because tyrosine is catalyzed by tyrosine hydroxylase to produce the precursor of DA, dihydroxyphenylalanine, i.e., DOPA.”
BackgroundMetabolomic profiling of cannabis use and cannabis intoxication in humans
Madrid-Gambín, F., Haro, N., Mason, N. L., Mallaroni, P., Theunissen, E. L., Toennes, S. W., Pozo, Ó. J., & Ramaekers, J. G. (2025) · Neuropsychopharmacology · doi:10.1038/s41386-025-02082-7 · Cited by 7 · see citing works
“For instance, tyrosine is known as a precursor of the neurotransmitter dopamine [52, 53], while isoleucine and leucine transamination may contribute to glutamate synthesis [54, 55].”
L-Tyrosine Limits Mycobacterial Survival in Tuberculous Granuloma
Gao, Y., Li, J., Guo, X., Guan, L., Wang, J., Huang, X., Wang, W., & Yang, H. (2023) · Pathogens · doi:10.3390/pathogens12050654 · Cited by 7 · see citing works
UHPLC-QQQ-MS/MS method for the simultaneous quantification of 18 amino acids in various meats
Wang, M. Z., Guo, J., Lin, H., et al. (2024) · Frontiers in Nutrition · doi:10.3389/fnut.2024.1467149 · Cited by 6 · see citing works
Multi-omics signature of healthy versus unhealthy lifestyles reveals associations with diseases
Fu, G., Rushing, B. R., Graves, L. M., Nieman, D. C., Pellegrini, M. A., Soldano, M., Thompson, M. J., Sakaguchi, C. A., Pathmasiri, W., & Sumner, S. (2025) · Human Genomics · doi:10.1186/s40246-025-00817-7 · Cited by 6 · see citing works
“Nicotine in tobacco use has also been found to lead to an increase in dopamine levels [147].”
Peel, J., McNarry, M. A., Heffernan, S. M., Nevola, V. R., Kilduff, L. P., & Waldron, M. (2025) · American Journal of Physiology-Regulatory, Integrative and Comparative Physiology · doi:10.1152/ajpregu.00186.2024 · Cited by 6 · see citing works
Smid, D. J., Klous, L., Ballak, S. B., Catoire, M., de Hoogh, I. M., & Hoevenaars, F. P. M. (2025) · Frontiers in Physiology · doi:10.3389/fphys.2025.1539615 · Cited by 6 · see citing works
“Increasing tyrosine levels could increase brain catecholamine synthesis and thereby lead to improved cognitive performance and mood, especially under stressful conditions during which brain catecholamine levels may be reduced (Hase et al., 2015).”
Li, Y., Zheng, H., Chen, X., Zhu, B., Liu, T., & Yang, J. H. (2023) · Plants · doi:10.3390/plants12040875 · Cited by 6 · see citing works
“for human adults, while Arg has a beneficial effect on the regulation of nutrient metabolism to enhance lean tissue deposition and insulin resistance in humans [32,33].”
Li, Y., Bansal, S., Singh, B. B., et al. (2024) · Antioxidants · doi:10.3390/antiox14010024 · Cited by 5 · see citing works
“…in vivo, affecting several essential biochemical pathways that rely on tyrosine, including the synthesis of thyroid hormones [22], melanin, and several key neurotransmitters such as L-DOPA, dopamine, adrenaline, and noradrenaline, in line with physiological and cognitive changes [23,24].”
Smart Drugs in Cognitive Disorders
Phogat, J., Bali, A., & Kapoor, N. (2023) · Advances in bioinformatics and biomedical engineering book series · doi:10.4018/978-1-6684-6577-6.ch010 · Cited by 4 · see citing works
Plini, E. R. G., Melnychuk, M. C., Harkin, A., Dahl, M. J., McAuslan, M. J., Kühn, S., Boyle, R. T., Whelan, R., Andrews, R., Düzel, S., et al. (2023) · The journal of nutrition health & aging · doi:10.1007/s12603-023-2005-y · Cited by 5 · see citing works
“Remarkably, these effects were mostly appreciable under stressful conditions (i.e. cold exposure [58], extended wakefulness (59) and working memory load and task-switching (60, 61) – a comprehensive revision of this topic is beyond the scope of this work, for reviews please refer to (55-57).”
InfluentialPharmacological Strategies to Improve Mental Performance
Cutsem, J. V., & Pattyn, N. (2024) · Routledge eBooks · doi:10.4324/9781003378969-8 · Cited by 4 · see citing works
Mathar, D., Abdoust, M. E., Tuszus, D., Marrenbach, T., & Peters, J. (2022) · bioRxiv (Cold Spring Harbor Laboratory) · doi:10.1101/2022.02.09.479693 · Cited by 4 · see citing works
Liu, T., Fan, H., Lin, R.-X., et al. (2025) · Phytomedicine · doi:10.1016/j.phymed.2025.157601 · Cited by 3 · see citing works
Exploring the intersecting paths between metabolic disorders and neurological manifestations
Eissa, N., Chkier, D., Ahmed, A., Attia, R. T., Zia, M., Beiram, R., & Sadek, B. (2026) · Heliyon · doi:10.1016/j.heliyon.2026.e44658 · Cited by 3 · see citing works
Chang, R., Yan, J., Li, Y., Zhang, Y., Wu, K., & Yang, Y. (2023) · Microbial Pathogenesis · doi:10.1016/j.micpath.2023.106487 · Cited by 3 · see citing works
Hudson, B. T., Dubrof, S. T., Settles, S. E., Park, H. J., & Filipov, N. M. (2024) · Nutritional Neuroscience · doi:10.1080/1028415x.2024.2344138 · Cited by 3 · see citing works
“Additionally, tyrosine, an essential amino acid found in eggs, is a DA precursor; thus enhanced neurotrans-mission of dopamine following supplementation that contained egg yolk could be associated with its tyrosine content [35,36].”
Au@Ag nanoparticles: an analytical tool to study the effect of tyrosine on dopamine levels
Minj, A., Sahu, S., Tanwar, L. K. S., & Ghosh, K. K. (2024) · RSC Advances · doi:10.1039/d4ra01872a · Cited by 3 · see citing works
Parthimos, T. P., Schulpis, K. H., Karousi, A. D., Loukas, Y. L., & Dotsikas, Y. (2022) · Applied Neuropsychology Adult · doi:10.1080/23279095.2022.2043327 · Cited by 3 · see citing works
“Previous research has mentioned short-term improvements in working memory, response inhibition, task switching, and executive functions after supplementation with Tyr (Hase et al., 2015; Jongkees et al., 2015).”
The Effects of Postpartum Yak Metabolism on Reproductive System Recovery
Shu, S., Fu, C., Wang, G., & Peng, W. (2022) · Metabolites · doi:10.3390/metabo12111113 · Cited by 3 · see citing works
“Trp is converted to pyruvate, which decarboxylates to produce acetoacetic acid [47]; Tyr synthesizes fumaric acid and acetoacetic acid through an oxidation and hydrolysis [48,49].”
BackgroundCai, Y., Deng, Z., Yang, Q., Pan, G., Liang, Z., Yang, X., Song, J., Xiao, X., & Li, S. (2024) · Frontiers in Immunology · doi:10.3389/fimmu.2024.1335042 · Cited by 3 · see citing works
Li, J., Mei, P.-C., An, N., Fan, X., Liu, Y., Zhu, Q., & Feng, Y. (2025) · Metabolites · doi:10.3390/metabo15030179 · Cited by 3 · see citing works
“These molecules play essential roles in regulating mood, cognitive functions, and stress responses [65–67].”
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- Authors
- Hase, A., Jung, S. E., & aan het Rot, M.
- Affiliations
- University of Groningen (NL)
- Corresponding author
- Hase, Adrian
- ORCID
- Hase, Adrian
- Venue
- Pharmacology Biochemistry and Behavior
- Publisher
- Elsevier BV
- Published
- 2015-06
- Volume
- 133
- Pages
- 1-6
- ISSN
- 0091-3057 (ISSN-L)
- OpenAlex
- W2064512986
- Cited by
- 91
- References
- 37
- Citations by year
- 2026: 12 · 2025: 23 · 2024: 17 · 2023: 11 · 2022: 9 · 2021: 7 · 2020: 1 · 2019: 3 · 2018: 3 · 2017: 3 · 2016: 1
- FWCI
- 1.46
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Pharmacology Biochemistry and Behavior (publishedVersion)
- PubMed (publishedVersion)
- University of Groningen research database (University of Groningen / Centre for Information Technology) (publishedVersion, other-oa)
- University of Groningen research database (University of Groningen / Centre for Information Technology) (submittedVersion, other-oa)
- Funders
- Netherlands Organization for Scientific Research (451-09-013)
- Topics
- Health Sciences › Medicine › Physiology › Adipose Tissue and Metabolism
- Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neurotransmitter Receptor Influence on Behavior
- Life Sciences › Neuroscience › Behavioral Neuroscience › Stress Responses and Cortisol
- Keywords
- tyrosine, catecholamines, dopamine, norepinephrine, working memory, cognitive load, exercise performance, acute supplementation
- MeSH terms
- Brain, Cognition, Emotions, Exercise Test, Humans, Norepinephrine
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