Tyrosine is an amino acid found in meat proteins. Your body uses it as a starting material to make several neurotransmitters (chemicals that help the brain and nervous system function). Based on this fact, tyrosine has been proposed as a treatment for various conditions in which mental function is impaired or slowed down, such as fatigue and depression. It has also been tried for attention deficit disorder (ADD).

Your body makes tyrosine from another common amino acid, phenylalanine, so deficiencies are rare; however, they can occur in certain forms of severe kidney disease as well as in phenylketonuria (PKU), a metabolic disorder that requires complete avoidance of phenylalanine.

Good sources of tyrosine include dairy products, meats, fish, and beans.