ABSTRACT
Aspartame is approximately fifty percent phenylalanine by weight. Persons with phenylketonuria (PKU) are unable to convert phenylalanine into tyrosine because of a defect in or a deficiency of the enzyme phenylalanine hydroxylase. The phenylalanine content of aspartame is of little concern in normal individuals and individuals heterozygous for PKU because of its rapid rate of metabolism. However, the amount of phenylalanine supplied by aspartame must be considered carefully in homozygous patients with classic PKU. The usual treatment for newly diagnosed PKU infants and children is a phenylalanine-restricted diet administered from infancy through childhood. The amount of phenylalanine provided by a normal diet is much larger than that likely to be ingested as aspartame. Phenylalanine and tyrosine concentrations are expressed as milligrams per deciliter, since those are the units used by most PKU patients. Aspartame ingestion for the pregnant PKU homozygous women is not recommended.
