Explanation

Phenylketonuria (PKU) is a problem with your metabolism, in which your body cannot process a substance called phenylalanine (Phe) properly. Phe is a substance that is found in a lot of foods. Your body needs it to work properly, but too much of it can be harmful.

If you have PKU, you don't have enough of the enzyme that breaks down Phe. This means that too much Phe builds up in your body, especially in your brain, where it can cause very serious and permanent damage.

Phe is found in all foods that contain protein, like meat, eggs, and nuts. It is also found in most foods that contain wheat, like pasta and bread, and some fruit, like oranges and cherries.