Tyrosine, also known as 4-hydroxyphenylalanine or L-tyrosine, is a nonessential amino acid that the body synthesizes from another amino acid called phenylalanine. It is named from the Greek tyros , which translates to "cheese," because it is found in the casein protein in cheese and other dairy products. Other natural food sources include fish, avocados, bananas, lima beans, almonds, peanuts, and sunflower and pumpkin seeds.
This amino acid plays an important role in metabolism. On the one hand, it interacts with proteins that undergo signal transduction to initiate various cellular processes. Receptor tyrosine kinases serve as pathways for transporting phosphate compounds in a process known as phosphorylation to produce phosphotyrosine. These activities involve virtually every protein in the body and are responsible for regulating the manufacture of various enzymes. In addition, tyrosine is a precursor to several other substances, including neurotransmitter chemicals in the brain, hormones produced by the thyroid, pituitary, and adrenal glands, and the skin pigment melanin.
Specifically, tyrosine is necessary for the body to synthesize serotonin, dopamine, epinephrine, and norepinephrine. These neurotransmitters are involved with signaling between nerve cells and synapses in the brain. These agents also affect mood and libido, which is why these substances are sometimes called "feel good hormones." In fact, several studies indicate that supplementation of this amino acid can help relieve chronic stress, anxiety and mild depression.
A true tyrosine deficiency is rare, but abnormal utilization occurs in certain syndromes. For example, oculocutaneous albinism is characterized by an inability to synthesize melanin from the amino acid. Phenylketonuria is characterized by the inability to synthesize phenylalanine into tyrosine, a condition that can lead to brain damage. While this condition may constitute a deficiency, dietary phenylalanine should be strictly avoided and tyrosine supplementation should be monitored. Low levels can also equate to low levels of the thyroid hormone thyroxine, a condition that can promote hypothyroidism and impaired central nervous system function.
As there are few cases where a tyrosine supplement is needed, there are no standard dietary recommendations. However, in the absence of rare syndromes such as those listed above, a low level may be indicated by low body temperature or low blood pressure. Consultation with a qualified healthcare professional is recommended before supplementing with this amino acid.
If tyrosine supplementation is deemed necessary, it is available in tablet or capsule form in units of between 50-1,000 mg. To facilitate absorption, it is recommended to take supplements with a meal that includes carbohydrates, preferably just before bedtime. Additionally, taking vitamin B6, folic acid, or vitamin B9 as folic acid, and copper also helps increase the absorption of this amino acid.