Plasma amino acid levels after single-dose aspartame consumption in phenylketonuria, mild hyperphenylalaninemia, and heterozygous state for phenylketonuria.

Aspartame (N-aspartyl-phenylalanine methyl ester), a widely used artificial sweetener, is hydrolyzed in the intestinal lumen to methanol and to its constituent amino .acids phenylalanine and aspartic acid. Ingestion of this sweetener causes a sharp increase in plasma phenylalanine I vels in normal persons. and in patients with phenylketonu ia.2The label on aspartame-containing products includes a warning to patients with PKU, but no information on the a tual sweetener content, and there is concern that aspart me ingestion by those who do not have PKU could p oduce phenylalanine levels sufficiently high to harm the b ain, especially among the estimated 2% of the general pulation who carry the gene for PKU and thus have a r~uced capacity for phenylalanine metabolism. Studies in rAtsshow that elevations of plasma phenylalanine levels, as