What does “Phenylketonurics: Contains Phenylalanine” mean?

Some food products include the warning: Phenylketonurics: Contains Phenylalanine. If you have seen a nutrition label with these scary words and wondered what they mean exactly, this quick post is for you!

Phenylketonurics: Contains Phenylalanine

The warning contains three words, two of which are not in most peoples’ everyday language: Phenylketonurics and phenylalanine. What do they mean? Simply put, “Phenylketonurics” means “People who suffer from Phenylketonuria”, whilst “phenylalanine” is the name of a particular essential amino acid which cannot be made in the human body. Phenylketonuria, commonly known as PKU, is a genetic disease. People with PKU have difficulty in metabolising phenylalanine.

The warning is directed at this unfortunate group of people, because they need to limit their intake of phenylalanine. If you don’t have PKU, there is no need to be concerned about it.

PKU Symptoms and Treatment

PKU is an incurable condition which when untreated can result in microcephaly (abnormally small head) and many mental disorders and intellectual disabilities. There are a couple of different types of PKU, and if you had it you would probably already know about it. Newborn babies in Australia are screened for it soon after birth, so that sufferers can be treated as soon as possible. The treatment rests on strictly controlling the amount of phenylalanine intake. This is achieved through diet formulations, protein supplements, and enzyme substitutions.

Foods containing Phenylalanine

Phenylalanine is found in a large number of foods, including chicken, eggs, milk, beef, soybeans, and pork. These natural sources are well known so people with PKU (Phenylketonurics) know to avoid and regulate their diets around them. For this reason, there is no need to include food warnings on every carton of eggs and every block of tofu. However, for foods which are artificially formulated with phenylalanine-containing ingredients, it becomes necessary to give Phenylketonurics the heads-up.

Aspartame breaks down to Phenylalanine

The main reason foods carry the PKU warning is our old friend aspartame, which we’ve written about here and here and elsewhere. When aspartame metabolises (as your body digests it), it forms phenylalanine. The unwanted build-up of phenylalanine in the bodies of Phenylketonurics may be significantly worsened by the unknowing consumption of aspartame-sweetened products like diet coke. Hence the warning!