What does the phenylketonuria warning label on products containing aspartame mean?

Prof. Walker: Phenylketonuria (PKU) is a rare hereditary disease where affected individuals lack the enzyme to properly metabolise phenylalanine, an amino acid. People suffering from phenylketonuria need to restrict their intake of phenylalanine from all sources including common protein foods such as meat and milk, and products containing aspartame. The labelling informs PKU sufferers of the presence of phenylalanine in the product. The wording of the label varies by country. In countries such as Canada, the European Union and Japan, the label is written as "aspartame, contains a source of phenylalanine", and in the United States the label is written as "Phenylketonurics: contains phenylalanine." Why was cyclamate banned in the United States? Prof. Walker: Cyclamate was banned in the United States after a study showed that some rats developed bladder cancer when fed extremely high amounts of a cyclamate and sodium saccharin mixture. Several further studies in rats and mice have since ... more