Get a nutritional boost with Swanson DL-Phenylalanine (DLPA)! A great source of amino acid precursors for neurotransmitters that support brain health, DL-phenylalanine is an essential amino acid that cannot be made in the body and must be supplied by food. Your body converts phenylalanine into L-tyrosine, which is then used to make dopamine, norepinephrine and adrenaline. Supplementing with phenylalanine may support a positive outlook.