Tyrosine

Latest Edit: Iva Lloyd, ND 2017-05-05 (EDT)

Tyrosine is a conditionally essential amino acid which is also synthesized by phenylalanine. Tyrosine becomes essential during times when hepatic conversion of L-phenylalanine to L-tyrosine is impaired such as during infection, trauma, chronic illness, liver disease, and other forms of severe stress.

Food Sources

The following foods have the highest concentration of Tyrosine.

The following is a list of some of the uses for tyrosine. ^[1]

Neurotransmitter function: L-tyrosine is important because it is the precursor for many neurotransmitters in the central nervous system such as L-dopa, dopamine, norepinephrine, and epinephrine. Vitamin B6, copper, and folic acid are needed for these conversions.
Hormone function: Tyrosine also has adaptogenic qualities because it is the precursor to epinephrine and norepinephrine. Furthermore, tyrosine is the precursor to thyroid hormone, enkephalins (analgesic peptides), melanin (the pigment responsible for skin colour), and many other substances in the body.
Thyroid function: Tyrosine is necessary to convert T4 to T3 via the liver. Also helpful in the conversion of rT3 back to T3.
Tyrosine is also considered a mild antioxidant.
Alcohol withdrawal support
Phenylketonuria: PKU can often lead to a deficiency of tyrosine and therefore individuals with this conditions are often supplemented with tyrosine.

Deficiency may lead to: ^[1]

impaired thyroid function: tyrosine is a precursor to thyroid hormone
low adrenal function: tyrosine is a precursor to catecholamines which are produced by the adrenals
low levels of tyrosine may be present in individuals with depression
predisposition to skin cancer due to a lack of melanin
tyrosine deficiency can develop during an extended period of protein loss (such as with nephrotic syndrome)

Excessive levels of tyrosine may lead to: ^[1]

Tyrosine is available in capsules, powder, and tablets.
The only established RDA is for adults at 1 gm. To determine what your specific requirements are talk to your naturopathic doctor or other trained medical professional.

General Adverse Effects: nausea, diarrhea, vomiting, nervousness
Pregnancy and Breastfeeding: Evidence is lacking to confirm lack of adverse effects to fetus or breastfeeding infants.
Adverse effects in specific populations: hyperthyroidism, Tourette's syndrome, schizophrenia; exogenous tyrosine could also promote cancer cell division in susceptible individuals.
Contraindications: migraine; in individuals with inborn errors of metabolism, alkaptonuria and tyrosinemia types I and II; tyrosine and phenylalanine should be avoided in cancer (especially pigmented melanoma); hypersensitivity to tyrosine

Drug Interactions include:^[1]

Imipramine and Related Tricyclic Antidepressants - Co-administration may facilitate withdrawal in cocaine addiction.
Levodopa and Related Antiparkinsonian Medications - L-tyrosine may be beneficial however, limited knowledge regarding potential issues of competition in absorption, transport system, and brain uptake; more research is warranted.
Levothyroxine and Related Thyroid Hormones - additive interaction is probable with co-administration but possibly with minimal effect in individuals whose thyroid gland has atrophied from chronic use of synthetic thyroid medication.

Amphetamines and Related Stimulant Medications - Co-administration may reverse or prevent tyrosine depletion caused by drug and support activity of drug therapy by enhancing precursor availability.
Oral Contraceptives - Drug can decrease plasma tyrosine levels, alter neurotransmitter levels, and potentially contribute to or exacerbate OC adverse effects.

Monoamine Oxidase (MAO) Inhibitors - Avoid concomitant use due to risk of hypertensive crisis. Also avoid L-tryptophan, 5-HTP, and phenylalanine.

Nutrient interactions include:^[1]

5-Hydroxytryptophan (5-HTP) - Tyrosine and 5-HTP may be beneficial together in the treatment of depression.
Branched-Chain Amino Acids - Branched-chain amino acids compete with tyrosine for transport across the blood-brain barrier. Separate intake of tyrosine and other amino acids and high-protein meals by at least 2 hours.
Iodine - Tyrosine and iodine have been used to support the synthesis of thyroid hormones but sufficient evidence of its efficacy is lacking.
Phenylalanine - Because of the possible additive effect, avoid unmonitored concomitant administration in the treatment of depression. Food sources containing both are generally considered safe at usual levels of intake.