L-tyrosine is one of the 20 amino acids required by your body to synthesize enzymes and proteins that control virtually cellular processes in your tissues and organs. While you can get L-tyrosine from dietary sources, it is considered a non-essential amino acid because it can be synthesized by your body from another similar amino acid called phenylalanine.
Biological Role of L-Tyrosine
In addition to its role in protein structure and function, L-tyrosine is also a precursor molecule for the synthesis of several neurotransmitters including dopamine and epinephrine. Neurotransmitters are chemical messengers for your nerve cells and affect many basic functions including your sense of well-being, or mood. According to the University of Maryland Medical Center (UMMC), L-tyrosine is also involved in the production of skin pigment, or melatonin, and hormone production in endocrine glands and some organs.
L-Tyrosine and Phenylketonuria
While it is rare to suffer from deficiencies in L-tyrosine, it may occur in people who suffer from phenylketonuria. This inherited disease results in the inability of an individual to metabolize the amino acid phenylalanine. Phenylketonuria can cause serious developmental defects including mental retardation, seizures, tremors and disproportionate head and limb sizes. Sufferers of phenylketonuria must avoid all dietary sources of phenylalanine and since their bodies synthesize L-tyrosine from phenylalanine, they may be L-tyrosine deficient.
Sources of L-Tyrosine
Even though L-tyrosine is considered non-essential, you should still be getting some of it through nutritional means. Since L-tyrosine is a structural component of protein, foods that are rich in protein are good sources of L-tyrosine. Healthy food choices for L-tyrosine include nuts and seeds, dairy foods, bananas, Lima beans and avocados. In addition to food sources, L-tyrosine is available as a dietary supplement. However, you should always discuss dietary supplements with your doctor prior to adding them to your diet.
Dosage and Toxicity of L-Tyrosine
According to the UMMC, recommended doses of L-tyrosine can vary between 500 to 1,000 mg, up to 3 times daily. The Material Safety Data Sheet for L-tyrosine lists the lethal dose concentration for 50 percent death in rats, also known as LD50, at over 5000 mg per kg. This means that for an average adult that weighs 165 lbs., which is roughly 75 kg, a dose of 375 g, or 375,000 mg, of L-tyrosine, might prove lethal. Overall, the toxicity of L-tyrosine appears to be fairly low. However, according to the UMCC, you should avoid L-tyrosine supplementation if you are currently taking some medications including thyroid hormone, L-dopa or monoamine oxidase inhibitors.
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