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PKU Disease in Newborns

written by: Diana Cooper • edited by: Lisa Lambson • updated: 3/9/2010

Learn about PKU disease and why it is important to have your newborn tested. Understand the PKU diet and know what foods need to be avoided and limited to promote a healthy life.

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    PKU Disease

    PKU (Phenylketonuria) is a genetic disease, caused by the absence of an enzyme (phenylalanine hydroxylase) that is necessary for the metabolism of the essential amino acid phenylalanine.

    Newborns with PKU disease appear normal, most often with blond hair, blue eyes, and fair skin. Without treatment, the infant fails to thrive and develops vomiting and eczematous rashes. By about six months of age, the infant exhibits behaviors indicative of mental retardation and other central nervous system (CNS) involvement. Symptoms include hyperactivity, irritability, seizures, and unpredictable, erratic behavior. Bizarre behavior patterns are common, such as screaming episodes, disorientation, failure to respond to strong stimuli, and catatonic-like positions.

    Newborns are tested after having ingested dietary protein (breast of bottle fed) for 24-48 hours. The blood test is mandatory for all newborns in most states.

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    PKU Diet

    The main treatment for PKU disease is a strict diet with minimal intake of phenylalanine, mostly found in protein-rich foods. If treatment is begun before three months of age, CNS damage can be minimized.

    PKU diets use to be considered safe to stop in adolescence but it is now recommended to continue the diet for life.

    The amount of phenylalanine allowed differs with each person. Blood levels need to be monitored closely so only safe amounts of phenylalanine will be ingested; just enough needed for normal growth and body processes.

    Infants will need a special formula that is phenylalanine-free. A dietitian will calculate how much breast milk or infant formula can be added to their diet. As they develop into children and adults, they will continue drinking a similar formula because it provides the protein in a form that is safe for individuals with PKU disease.

    All high protein foods must be avoided. This includes meat, fish, milk products, eggs, beans, and nuts. Because only small amounts of phenylalanine are allowed in the PKU diet, foods such as bread, pasta, rice, bakery goods, and even some fruits and vegetables should be limited.

    Aspartame (NutraSweet) should be avoided because it is converted into phenylalanine in the gut. This artificial sweetener can be found in diet sodas, medications, and chewable vitamins.

    Reading food and beverage labels closely, measuring just the right portions, and keeping close records of daily phenylalanine intake is necessary for good health with those who have PKU disease. Sticking with a PKU diet can be challenging but it is not impossible.

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    Disclaimer

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