L-Phenylalanine
This amino acid has been shown to have positive results in the treatment of skin disorders, pain, and depression. This amino acid is produced in part by the body, but not in sufficient amounts. It must also be obtained through plant and animal sources in the diet. The body must have L-Phenylalanine in order to create proteins and other necessary molecules, including dopamine, epinephrine, tyrosine, and norepinephrine.