Final answer:
People with PKU should avoid aspartame sweetener due to the risk of phenylalanine build up.
Step-by-step explanation:
People with PKU should avoid aspartame sweetener.
Aspartame is broken down by the body into three molecules: aspartic acid, phenylalanine, and methanol. Individuals with PKU lack the enzyme needed to metabolize phenylalanine, which is released when aspartame is broken down. Therefore, consuming aspartame can be harmful to people with PKU as it can cause phenylalanine to build up to toxic levels in the body.