L-tyrosine is an essential amino acid (protein building block) that the body synthesizes from phenylalanine, another amino acid. Tyrosine is important to the structure of almost all proteins in the body. It is also the precursor of several neurotransmitters, including dopamine.

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.

L-tyrosine has not been reported to cause any serious side effects. However, Vitamin B6, folic acid, and copper are necessary for conversion of L-tyrosine into neurotransmitters. A dietary deficiency of tyrosine may reduce the effectiveness of amphetamines. Adequate tyrosine intake from dietary protein or supplements is necessary in individuals taking ADD stimulant medications (amphetamines).