Tyrosine

Overview

Tyrosine is a non-essential amino acid synthesized in the body from the essential amino acid phenylalanine. Tyrosine is the direct precursor to several neurotransmitters, including epinephrine, norepinephrine, dopamine, and L-dopa.

Dosage Info

Dosage Range

1 to 10 grams daily.

Most Common Dosage

500mg, 3 times daily.

Dosage Forms

Tablets, capsules, powder, and liquid.

Adult RDI

None established

Adult ODA

None established

RDA

• : None established

Interactions and Depletions

Depletions

• Oral contraceptives

Active Forms

L-tyrosine.

Absorption

Like other amino acids, tyrosine is absorbed from the gastrointestinal tract following protein digestion in the stomach.

Toxicities & Precautions

General

Tyrosine is generally considered to be quite safe and reports of toxicity are rare.

Side Effects

At extremely high doses, tyrosine may cause diarrhea, nausea, vomiting, or nervousness. These symptoms usually disappear when the dosage is lowered.

Functions in the Body

Clinical Applications

Depression

Because tyrosine is the precursor for dopamine and norepinephrine, it has been used with some success in the treatment of depression. (1) Some physicians also report that tyrosine can help alleviate the depression that often accompanies Parkinson’s disease and Alzheimer’s disease. (2) , (3) , (4)

PKU

This condition is a genetic inborn error of phenylalanine metabolism. Infants born with this condition have a defect in the enzyme that normally converts phenylalanine to tyrosine. Normal development is possible if the condition is caught early and a phenylalanine-elimination diet is instituted. (5) Another study involving PKU patients on an inadequate diet experienced high plasma phenylketonuria concentrations in comparison to patients on a controlled diet which could disrupt the conversion of phenylalanine to tyrosine. (6) In some cases, tyrosine supplementation helps support normal protein and catecholamine synthesis. (7) , (8)

Cocaine Addiction

Medical centers and substance abuse programs are using a formula containing tyrosine along with other supplements to treat cocaine addiction. Chronic euphoria depends on dopamine activation, which depletes brain stores of dopamine and creates the craving for more. Tyrosine helps the body synthesize more dopamine rather than relying on cocaine. (9)

Symptoms and Causes of Deficiency

Tyrosine deficiency is most frequently seen in countries where there is inadequate protein in the daily diet. However, individuals with achlorhydria or hypochlorhydria (inadequate production of hydrochloric acid) may not digest proteins properly, which could lead to amino acid status disturbances. Tyrosine can become “conditionally essential” in conditions or diseases where there is a dependence on tyrosine status for homeostasis.

Since tyrosine is a precursor for thyroid hormones, a deficiency may lead to under active thyroid or overt hypothyroidism.

Since tyrosine is the precursor for brain neurotransmitters that regulate moods and emotions, a deficiency may lead to depression, craving behavior, or other types of psychological and emotional disturbances.

Reduced conversion of phenylalanine to tyrosine caused tyrosine deficiency in patients suffering from end-stage renal disease (ESRD). Supplementation of tyrosine may be required. (10)

Dietary Sources

Dairy products, meats, fish, wheat, oats, and many other foods contain tyrosine.

References

1. View Abstract: Gelenberg AJ, Gibson CJ. Tyrosine for the treatment of depression. Nutr Health. 1984;3(3):163-73.
2. Braverman ER, et al. The Healing Nutrients Within. New Canaan, CT: Keats Publishing; 1997:59-68.
3. View Abstract: Meyer JS, et al. Neurotransmitter precursor amino acids in the treatment of multi-infarct dementia and Alzheimer’s disease. J Am Geriatr Soc. Jul1977;25(7):289-98.
4. View Abstract: Growdon JH, et al. Effects of oral L-tyrosine administration on CSF tyrosine and homovanillic acid levels in patients with Parkinson’s disease. Life Sci. Mar1982;30(10):827-32.
5. View Abstract: Mira NV, Marquez UM. Importance of the diagnoses and treatment of phenylketonuria. Rev Saude Publica. Feb2000;34(1):86-96.
6. View Abstract: Schulpis KH, Papassotiriou I, Vounatsou M, Karikas GA, Tsakiris S, Chrousos GP. Morning preprandial plasma ghrelin and catecholamine concentrations in patients with phenylketonuria and normal controls: evidence for catecholamine-mediated ghrelin regulation. J Clin Endocrinol Metab. Aug2004;89(8):3983-7.
7. View Abstract: van Spronsen FJ, van Rijn M, Bekhof J, et al. Phenylketonuria: tyrosine supplementation in phenylalanine-restricted diets. J Inherit Metab Dis. Feb2001;73(2):153-7.
8. View Abstract: Rohr FJ. Tyrosine supplementation in the treatment of maternal phenylketonuria. J Clin Nutr. Mar1998;67(3):473-6.
9. Blum K, et al. Reduction of both drug hunger and withdrawal against advice rate of cocaine abusers in a 30 day inpatient treatment program by the neuronutrient Tropamine. Curr Ther Research. 1988;43:1204.
10. View Abstract: Boirie Y, Albright R, Bigelow M, Nair KS. Impairment of phenylalanine conversion to tyrosine in end-stage renal disease causing tyrosine deficiency. Kidney Int. Aug2004;66(2):591-6.