Final answer:
Phenylketonurics: Contains Phenlalanine __ mg label is required on products that contain aspartame due to difficulties in phenylalanine metabolism for individuals with PKU.
Step-by-step explanation:
Phenylketonurics: Contains Phenlalanine __ mg label is required on products that contain aspartame because people with phenylketonuria (PKU) are unable to properly break down phenylalanine. PKU is a metabolic disorder where individuals lack sufficient activity of the enzyme phenylalanine hydroxylase. Phenylalanine can accumulate in the body and cause damage to the central nervous system and brain if not properly managed.