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Treatments and drugs
By Mayo Clinic staffThe main phenylketonuria treatment is a strict diet with very limited intake of phenylalanine, which is mostly found in protein-rich foods. Doctors used to believe it was OK for a person with PKU to stop the diet in adolescence, but today, doctors recommend sticking to the diet for life.
A safe amount of phenylalanine differs for each person. Your doctor will determine a safe amount through regular review of diet records, growth charts and blood levels of phenylalanine. Frequent blood tests will monitor PKU levels as they change over time, especially during childhood growth spurts and pregnancy. In general, the idea is to consume only the amount of phenylalanine that's necessary for normal growth and body processes, but no more.
Which foods to avoid
Because the amount of phenylalanine adults can safely eat is so low, it's crucial they avoid all high-protein foods, including:
- Milk
- Eggs
- Cheese
- Nuts
- Soybeans
- Beans
- Chicken
- Steak and other beef products
- Fish
- Chocolate
- Peas
Children and adults should also avoid foods, including many diet sodas, and medications made with aspartame (NutraSweet, Equal). Aspartame, found in many artificial sweeteners, releases phenylalanine when digested.
Adults and children with PKU also have to limit foods, such as:
- Pasta
- Rice
- Bread
- Cookies
- Certain fruits and vegetables
Too much of a good thing can sometimes be harmful. Even if you're eating approved foods, eating too many at one time can be dangerous. Consider the total amount of phenylalanine in all the foods you eat when planning your diet.
Formula for babies
You might wonder how someone, particularly a baby, can get all of the necessary nutrition with these dietary limitations. The answer is a formula — a special nutritional drink or supplement for people with PKU. The phenylalanine-free formula provides protein and other essential nutrients in a form that is safe for people with PKU.
Because regular infant formula and breast milk contain phenylalanine, babies with PKU need to have their diets substituted with a phenylalanine-free infant formula. A dietitian will carefully calculate a sparing amount of breast milk or regular formula to be mixed with the phenylalanine-free formula. Parents introduce solid foods with low levels of phenylalanine to children with PKU on the same schedule used for other infants. These foods replace the phenylalanine a baby has been receiving from breast milk or formula and need to be precisely figured into the daily phenylalanine intake.
Formula for older children and adults
Older children and adults continue to drink several glasses of formula each day, as directed by a doctor or dietitian. The formula for older kids and adults is not the same as the one used for infants, but it works on the same principle. It acts as a nutritional substitute and is continued for life.
The need for a nutritional supplement, especially if your child doesn't find it palatable, and the limited food choices can make the PKU diet challenging. But, it's the only way to prevent the serious health problems people with PKU can develop. Families need to commit to this lifestyle change wholeheartedly, realizing that it may be difficult but not impossible.
PKU medication
The Food and Drug Administration (FDA) has approved the drug sapropterin (Kuvan) for treatment of some people with PKU. The drug is for use in combination with a PKU diet. In approving the drug, the FDA directed that studies continue regarding the drug's efficacy and long-term safety.
- Bodamer OA. Overview of phenylketonuria. http://www.uptodate.com/home/index.html. Accessed Aug. 18, 2009.
- Phenylketonuria. Genetics Home Reference. http://ghr.nlm.nih.gov/condition=phenylketonuria. Accessed Aug. 27, 2009.
- PKU (Phenylketonuria). March of Dimes. http://www.marchofdimes.com/professionals/14332_1219.asp. Accessed Aug. 24, 2009.
- Longo Nicola. Inherited disorders of amino acid metabolism in adults. In: Fauci AS, et al. Harrison's Principles of Internal Medicine. 17th ed. New York, N.Y.: McGraw Hill Medical; 2008. http://www.accessmedicine.com/content.aspx?aID=2882866. Accessed Aug. 27, 2009.
- Amino acid and organic acid metabolism disorders. The Merck Manuals: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/print/sec19/ch296/ch296c.html. Accessed Aug. 27, 2009.
