L-Tyrosine

L-tyrosine is a nonessential amino acid that the body makes from phenylalanine. Tyrosine is important to the structure of almost all proteins in the body. It is also the precursor of several neurotransmitters, including L-dopa, dopamine, noradrenaline, and adrenaline.
L-tyrosine, through its effect on neurotransmitters, may affect several health conditions, including Parkinson's disease, depression, and other mood disorders. Studies have suggested that tyrosine may help people with depression. Preliminary findings indicate a beneficial effect of tyrosine, along with other amino acids, in people affected by dementia, including Alzheimer's disease. Due to its role as a precursor to noradrenaline and adrenaline (two of the body's main stress-related hormones) tyrosine may also ease the adverse effects of environmental, psychosocial, and physical stress.
L-tyrosine is converted by skin cells into melanin, the dark pigment that protects against the harmful effects of ultraviolet light. Thyroid hormones, which have a role in almost every process in the body, also contain tyrosine as part of their structure.
People born with the genetic condition phenylketonuria (PKU) are unable to metabolize the amino acid phenylalanine. Mental retardation and other severe disabilities can result. While dietary phenylalanine restriction prevents these problems, it also leads to low tyrosine levels in many (but not all) people with PKU. Tyrosine supplementation may be beneficial in some people with PKU, though the evidence is conflicting.
Dairy products, meats, fish, wheat, oats, and most other protein-containing foods contain tyrosine.
L-tyrosine has been used in connection with the following conditions: Depression, phenylketonuria (for deficiency), alcohol withdrawal support, Parkinson's disease.
Some people affected by PKU are deficient in tyrosine. Tyrosine levels are occasionally low in depressed people. Any person losing large amounts of protein, such as those with some kidney diseases, may be deficient in several amino acids, including tyrosine.
Some human research with people suffering from a variety of conditions used 100 mg of L-tyrosine per 2.2 pounds of body weight, equivalent to about 7 grams per day for an average-sized person. The appropriate amount to use in people with PKU is not known, therefore, the monitoring of blood levels by a physician is recommended.
L-tyrosine has not been reported to cause any serious side effects. However, it is not known whether long-term use of L-tyrosine, particularly in large amounts (such as more than 1,000 mg per day) is safe. For that reason, long-term use of L-tyrosine should be monitored by a doctor.
Vitamin B6, folic acid, and copper are necessary for conversion of L-tyrosine into neurotransmitters.