LowproteinLIVING

What is Phenylketonuria (PKU)?

PKU is an inherited disorder that affects about 1 in every 10,000 people. A person with PKU cannot break down the protein from food in the usual way. 

Protein is made up of separate “building blocks” called amino acids. One of these amino acids is called phenylalanine.  Protein is needed for cells in the body to grow, repair and function.

Phenylalanine is also involved in brain growth and sending nerve signals around the body.  A person with PKU does not produce the chemical needed to break down phenylalanine. As a result the level of phenylalanine builds up in their blood.  In a baby these high levels would result in brain damage.

Since 1969 all babies in the UK have their blood tested for phenylalanine in the first weeks of life. Infants found to have PKU are immediately started on a special diet to bring the blood levels down. This prevents any damage to the brain and enables normal development.

What is the PKU diet?

The only way to treat PKU is to restrict the amount of phenylalanine entering the blood. A PKU diet avoids food and drink that contain large amounts of phenylalanine.

Which foods must be avoided?

These are the foods that are high in protein. All meat, poultry, fish, eggs, cheese, pulses (beans and lentils), meat substitutes (e.g. soya products and Quorn™) and nuts must be avoided.

Where do people with PKU get their protein?

Protein in the PKU diet comes mainly from a special supplement drink or bar taken with a meal. The diet also contains weighed amounts of moderate protein foods called exchanges. Examples of exchange foods are potato, cereals and rice.

Which foods can be eaten freely?

Most fruits, some vegetables, salad, sugar, spices, herbs, oil, margarine and butter. Special low protein foods such as bread, pasta and biscuits can be prescribed by doctors and used in the normal way.

SHS International would like to thank Susan Durham-Shearer, Maggie Lilburn and Dr Philip Lee with the support of PKU patients at the Metabolic Clinic, University College London Hospital. First published in the PKU FiloFax 2001

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Series 2 - Understanding your PKU Diet