Scientific Name(s): 4-hydroxyphenylalanine, C9H11NO3
Common Name(s): L-tyrosine, Tyrosine
Drug class: Oral nutritional supplements
Medically reviewed by Drugs.com. Last updated on Dec 31, 2020.
There is no evidence to support the use of tyrosine in the metabolic genetic disorder phenylketonuria. Some evidence for improved cognitive performance in conditions of stress, including sleep deprivation, exists. Clinical trial data for other conditions is limited and does not support tyrosine supplementation, including for the enhancement of sports performance.
Limited clinical studies use 100 to 150 mg/kg per day. Manufacturers commonly recommend 500 to 1,500 mg/day, and dosages of more than 12 g/day are not recommended.
Tyrosine is contraindicated in hyperthyroidism or Graves disease because it may increase levels of thyroid hormone. Coadministration of tyrosine with monoamine oxidase inhibitors (MAOIs) is contraindicated.
Information regarding safety and efficacy in pregnancy and lactation is lacking.
Coadministration of tyrosine and MAOIs is contraindicated. Tyrosine could increase levels of thyroid hormone and levodopa.
Information is limited. Tyrosine supplementation may trigger migraine.
Information is limited.
Tyrosine is made endogenously from phenylalanine and can be found in soy products, milk, cheese, yogurt, chicken, turkey, fish, peanuts, almonds, bananas, lima beans, avocado, pumpkin seeds, and sesame seeds.Zimmermann 2001
The name tyrosine is derived from the Greek tyri, meaning "cheese." Tyrosine was first identified in cheese protein casein in 1846 by German chemist Justus von Liebig.
Tyrosine is a nonessential, yet indispensable, amino acid made endogenously and eaten in a usual diet. It is a fundamental building block for proteins, specifically for neurotransmitters. Tyrosine is converted to L-dopa, dopamine, epinephrine, norepinephrine, triiodothyronine (T3), thyroxine (T4), and melanin.
Uses and Pharmacology
Research reveals no recent animal data regarding the use of supplemental tyrosine for use in depression.
Despite a theoretical basis for the use of tyrosine in depression, studies conducted in the 1980s using small sample sizes did not show any benefit.Meyers 2000, Parker 2011 More recent studies focused on serotonin precursors, revealing little evidence of a place in therapy for tyrosine.Meyers 2000, Parker 2011, Fernstrom 2000
Research reveals no recent animal data regarding the use of supplemental tyrosine for the use of performance enhancement.
Limited clinical studies provide equivocal data on the effects of supplemental tyrosine in exercise,Chinevere 2002, Tumilty 2011 with older studies conducted in the 1980s reporting more positive findings. Among 8 cyclists exercising in heat, tyrosine 150 mg/kg appeared to improve endurance,Tumilty 2011 while a similar trial also conducted among cyclists resulted in increased plasma tyrosine levels but not improved performance; however, tyrosine may have altered their perception of fatigue.Chinevere 2002
The effect of tyrosine on core cognitive-control performance, as measured by stopping overt responses, was investigated in a small double-blind, randomized, placebo-controlled cross-over study in 22 young healthy female adults. One hour after administration of L-tyrosine 2 g (in 400 mL orange juice), participants were observed to more efficiently inhibit unwanted actions compared to the placebo phase (P<0.05). Response execution was not affected and no significant changes were found in physiological parameters (eg, blood pressure, heart rate) or mood.Colzato 2014
Tyrosine hydroxylase is the rate-limiting step in the production of L-dopa and dopamine, forming the basis for the use of supplemental tyrosine. However, clinical trial data supporting a place in therapy are lacking.Fernstrom 2000, Feve 2012
Tyrosine deficiency is rare, but possible among people with phenylketonuria because of their avoidance of phenylalanine-containing foods such as milk, eggs, and meat. Tyrosinemia is also rare.Glaeser 1979
Research reveals no recent animal data regarding the use of supplemental tyrosine in phenylketonuria.
A Cochrane meta-analysis of 6 trials with a total of 56 patients found that increased blood tyrosine levels result from supplementation. However, this does not translate to improvement in any outcome measures, including intelligence, neurophysiological performance, growth, nutritional status, quality of life, or mortality.Posner 2009 A case study suggests a role for tyrosine supplementation in patients with attention deficit hyperactivity disorder symptoms who also have phenylketonuria.Webster 2013
Research reveals no recent animal data regarding the use of supplemental tyrosine for the use of stress prevention. Tyrosine has been shown to impair enzymes of energy metabolism in the cerebral cortex of rats, but the implications of this finding are unclear.de Andrade 2012
Studies evaluating supplemental tyrosine's role in mitigating the effects of stress on cognitive performance and memory deficit have generally found positive, but limited, effects (and lesser than for amphetamine).Deijen 1999, Fernstrom 2000 Among military cadets (N = 21), cognitive performance was supported by tyrosine 10 g/day during physical and psychological training.Deijen 1999 Tyrosine 300 mg/kg in 2 divided doses mitigated the stress-related decrease in cognitive performance induced by cold immersion in another small study.Mahoney 2007 Following sleep deprivation, tyrosine 150 mg/kg improved some aspects of cognitive and motor performance in another small study.Magill 2003 At a dose of 100 mg/kg, L-tyrosine administered 90 minutes prior to heat exposure (45°C x 90 minutes) in 10 healthy young males from the Indian military mitigated the reduction in information processing and cognitive decline seen during the placebo phase of a double-blind, randomized, cross-over study. Tyrosine was also observed to increase plasma norepinephrine levels compared to placebo.Kishore 2013
Tyrosine is unable to cross the blood-brain barrier, despite brain tyrosine levels being dependent on plasma concentrations.Glaeser 1979 An alternative form, N-alpha-linolenoyl tyrosine, has been developed to overcome this issue.Yehuda 2002 Coadministration of tyrosine with vitamin B6, folate, and copper could enhance conversion of tyrosine to brain neurotransmitters.
Manufacturers commonly recommend 500 to 1,500 mg/day, and dosages of more than 12 g/day are not recommended.
Pregnancy / Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking.
Case reports are lacking; however, tyrosine is contraindicated in patients taking MAOIs, including isocarboxazid, phenelzine, tranylcypromine, and selegiline. Because tyrosine could increase levels of thyroid hormone and levodopa, caution is warranted.
Case reports are lacking; however, higher plasma tyrosine levels have been noted in cases of chronic migraine.D'Andrea 2013
Symptoms associated with hereditary tyrosinemia, including the development of skin and eye lesions, were apparent at plasma levels 10 times of that found following administration of tyrosine 150 mg/kg in clinical trials.Glaeser 1979 L-tyrosine has been safely used as an adjuvant in vaccine preparation.Baldrick 2002
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