Phenylketonuria (PKU) is a rare metabolic disorder that affects the way the body breaks down protein. This is a genetic disorder. Untreated children are severely impaired in their motor and especially mental development. PKU may cause mental disorders, epileptic seizures and general irritability. In addition, pigmentation problems of the skin and eczema-like skin lesions may occur. It is routine for newborns to have the level of phenylalanine in their blood checked on their fifth day of life, in order to begin treatment of affected children early enough.
An enzyme defect is the cause of PKU
The cause of PKU is an enzyme defect that prevents excess of the amino acid phenylalanine from being converted into the amino acid tyrosine. If PKU patients receive lots of phenylalanine in their diet, the concentration of the amino acid in the blood increases sharply. Phenylalanine then reaches the brain in large quantities and can cause considerable damage to the brain's development.
The urine of PKU patients therefore typically has a nail polish-like odour. As amino acid tyrosine is a scarce commodity, it is missing, for example, to produce hormones or the pigment melanin. Hence, PKU patients are often light blonde, have light eyes and pale skin.
PKU patients receive a special diet
If the diagnosis is made, a phenylalanine or low-protein diet must be started immediately. Only then is normal physical and mental development possible. However, PKU patients do require a small amount of phenylalanine, because amino acid is essential for life.
Infants receive special bottle diets with precisely calculated amounts of phenylalanine. Affected children must give up a lot, because all protein-rich foods, such as meat, eggs, fish, milk and cheese, contain large amounts of phenylalanine. There can also be small amounts in plant foods, such as cereals, vegetables and fruit. Special diets with a phenylalanine-free, amino acid mixture, enriched with vitamins and minerals where appropriate, help the child to follow a strict diet and meet the requirements for protein, vitamins and minerals. The necessary amount of this food is calculated based on the child's age and body weight and is constantly adapted to his or her needs.
Aspartame contains phenylalanine
If you suffer from PKU, you must also avoid the sugar substitute, aspartame. This is because aspartame contains phenylalanine, as does any food that has been sweetened with this sugar substitute. You can find information regarding the addition of aspartame on the food label.
It is recommended to have a lifelong diet
It is necessary to strictly comply with the diet, especially in the first ten to twelve years of life until the brain development and the development of the central nervous system are complete. Experts even recommend a lifelong phenylalanine-free diet to prevent poor concentration, slowed responsiveness and convulsions.
If you have PKU and are planning to have a child, you should observe a particularly strict diet in order to protect the unborn child. It is best to first consult a doctor about your particular situation.