What is phenylalanine in pickled ginger and is it bad for you?

Amino acid, no-maybe: You need phenylalanine in your diet as it is one of the essential amino acids that you cannot make. However, in this case the reason it is likely listed on the package is because the product probably has aspartame (an artificial sweetener that contains phenylalanine) in it and by law foods with aspartame must list it to warn people with the rare disease phenylketonuria that it has phenylalanine.