Miracon Science

L-Tyrosine

Synonym(s): tyrosine
Nutrient group: Amino acids

Sources and physiological effects

Dietary sources
L-tyrosine is one of the conditionally essential amino acids. In addition to external supply, it can also be synthesized endogenously from phenylalanine by hydroxylation. Under certain metabolic situations or certain liver diseases, this amino acid becomes essential. Various high-protein foods contain higher amounts of L-tyrosine. These include meat, salmon and chicken eggs as well as pumpkin seeds, walnuts, peanuts and unhulled rice. Cheese and curd cheese also contain L-tyrosine, especially in the casein component.  First isolated from cheese, L-tyrosine was also namend after it (Greek. "Tyros", „cheese“).
Physiological effects
Thyroid
  • Hormone synthesis of thyroxine and triiodothyronine 
Nervous system
  • Neurotransmitter synthesis (dopamine, norepinephrine and adrenaline) 
Skin
  • Precursor for the skin pigment melanin 

Recommended intake

Requirement
Recommended intake Adults: 13.7 mg/kg bw daily
Infants: 68 mg/kg bw daily 
Increased demand Newborns
Recommended intake according to the food labelling regulations 
(= 100 % TB marking on label)		  
  N/A  
Nutrient safety  
UL Long-term daily intake, at which no negative health effects are to be expected 150 mg/kg bw (according to Gröber: micronutrients 2011)
NOAEL Maximum intake, with no observed adverse effect  N/A

Detailed information

Physiological functions of L-tyrosine
As a precursor of the neurotransmitters dopamine, noradrenaline and adrenaline as well as the thyroid hormones thyroxine and triiodthyronine, it is involved in neurovegetative processes as well as in all metabolic processes.
L-tyrosine in depression and PMS
The substitution of L-tyrosine shows therapeutic benefits in depressive patients and in patients with Parkinson's disease. This appears to be caused by a direct effect on neurotransmitter activity. This correlation also explains the use of tyrosine and its precursor phenylalanine in pain conditions (1) and in PMS. (2)
L-tyrosine promotes stress resistance
Another indication area is in acute and chronic stress conditions. Here L-tyrosine can counteract a decrease in mental and physical performance and promote attention, vigilance and stress resistance. (3)
In chronic stress, norepinephrine levels are also lowered. This hormone, formed from tyrosine is an effective neurotransmitter of the sympathetic system and therefore an important substance for the avoidance of stress-induced damage. (3) Cognitive abilities can also be positively influenced by L-tyrosine, especially in stressful situations. (4)(5)
Performance in sport
L-tyrosine is used in sports to promote a healthy state of tension in the athlete before the competition (arousal state) (3). The stimulating effect is also used by healthy people to improve drive and performance and to promote concentration and alertness.

Deficiency symptoms

Impact on Symptoms
General well-being Diminished stress resistance, depressive moods, weakness
Nervous system Disturbed neurotransmitter synthesis (dopamine), reduced cognitive performance

Administration

General mode of administration
 
When		 L-tyrosine should be taken 30 minutes before a meal within the first half of the day.
  Notes:
  • Preventive: 400 – 800 mg 30 minutes before high mental or stress-related demands. For depression and pain the combination with L-tryptophan is suitable. Since the two amino acids have an opposite mechanism of action, L-tyrosine is recommended in the first half of the day, L-tryptophan in the second half of the day and before bed.
Side effects
In rare cases sleep disturbances occur.
Contraindications
Pregnancy and lactation

Interactions

Drug interactions
Antiparkinson medication
(L-dopa, carbidopa)		 Reduced absorption of L-dopa and L-tyrosine when administered simultaneously.
Thyroid hormones
(L-thyroxine)		 Can increase the effect of L-thyroxine as thyroid hormone precursor.
Estrogens / progestogen
(oral contraceptives)		 Combination of estrogens with progestogens may reduce plasma levels of tyrosine.
Nutrient interactions
Amino acids L-tryptophan, tyrosine, phenylalanine, valine, leucine and isoleucine hinder transport through the blood-brain barrier.
Phenylalanine and tyrosine show synergistic effects; high doses should nevertheless be avoided.

Description and related substances

Description
Proteinogenic, non-essential amino acids
Related substances
L-Tyrosine

References

References

1) Gröbe, U. 2002. Orthomolekulare Medizin. Ein Leitfaden für Apotheker und Ärzte.
2) Burgerstein, L. 2002. Handbuch der Nährstoffe.
3) Liebermann, H. R. 2003. Nutrition, brain function and cognitive performance. Appetite. 40(3):245-54.
4) Wiesel, F. A. et al. 2005. Kinetics of tyrosine transport and cognitive functioning in schizophrenia. Schizophr Res. 74:81-9.
5) O'Brien, C. et al. 2007. Dietary tyrosine benefits cognitive and psychomotor performance during body cooling. Physiol Behav. 90(2-3):301-7.

References Interactions
Stargrove, M. B. et al. Herb, Nutrient and Drug Interactions: Clinical Implications and Therapeutic Strategies, 1. Auflage. St. Louis, Missouri: Elsevier Health Sciences, 2008.
Gröber, U. Mikronährstoffe: Metabolic Tuning –Prävention –Therapie, 3.
Auflage. Stuttgart: WVG Wissenschaftliche Verlagsgesellschaft Stuttgart, 2011.
Gröber, U. Arzneimittel und Mikronährstoffe: Medikationsorientierte Supplementierung, 3. aktualisierte und erweiterte Auflage. Stuttgart: WVG Wissenschaftliche Verlagsgesellschaft Stuttgart, 2014.
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