Phenylketonuria

The right diet is the key to managing many diseases and to improving general quality of life. For this condition, scientific research has found benefit in the following healthy eating tips.

• Aspartame

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  Avoid phenylalanine by steering clear of soft drinks, candy, and other foods and drinks sweetened with aspartame (NutraSweet).

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  Aspartame

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  There is debate about whether it is safe for people with PKU to consume aspartame, a low-calorie sweetener that contains about 50% phenylalanine. In one study, blood levels of phenylalanine increased only slightly after people with PKU ingested a 12-ounce soft drink sweetened with aspartame.³⁰ However, that study did not address long-term effects of regular aspartame consumption. Until more is known, it is prudent for people with PKU to completely avoid aspartame-containing beverages and foods.

• Phenylalanine

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  Work with your healthcare provider and a nutritionist to maintain a nutritious phenylalanine-restricted diet, which usually means eliminating high-protein foods, such as dairy products, eggs, fish, meats, poultry, legumes, and nuts.

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  Phenylalanine

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  PKU can be controlled by a diet low in phenylalanine.³¹ The greatest benefits are achieved when the diet is started in the first few days of life,³² although later treatment will still help to reduce the severity of PKU-related conditions.^33,34,35 Maintaining low phenylalanine levels through dietary control improves muscle control and behavioral and intellectual function.^36,37

  The effects of elevated phenylalanine appear to be less severe in older children and adults than in newborns and young children, in whom the nervous system is still developing. This, combined with the difficulties inherent in following a strict lifelong diet, have caused researchers to examine whether the dietary regimen may be relaxed as children get older. While some research suggests that relaxation of dietary measures may not be harmful,^38,39,40 this has not been found to be true in all studies.⁴¹ Therefore, more research is needed to resolve this issue.^38,43 In a survey of 111 PKU treatment centers, 87% favored lifelong dietary restriction of phenylalanine.⁴⁴The PKU diet is strict, and should be undertaken with the help of a nutritionist and a physician.

  A PKU diet is low in protein, providing no more than the minimum amount of phenylalanine needed by the body. All high-protein foods, such as dairy products, eggs, fish, meats, poultry, legumes, and nuts, are usually eliminated.⁴⁵ Lower protein foods, such as fruits, vegetables and some grain products, are allowed in measured amounts, along with specially prepared phenylalanine-free or nearly phenylalanine-free foods. This diet is supplemented with an amino acid formula to increase protein intake without adding more phenylalanine than is nutritionally required.

  Phenylalanine levels fluctuate as a consequence of changes in diet, health, and growth; therefore, levels must be checked regularly.³⁶ A nutrition specialist can also provide information on homemade and specially prepared foods for people with PKU, including infant formulas, low protein pastas, breads, crackers, and other foods.

  People with PKU who are not following the PKU diet can become deficient in biotin, a water-soluble B vitamin. This is because phenylalanine blocks biotin metabolism. In a controlled study of children with PKU, elevated phenylalanine levels resulted in seborrheic dermatitis caused by biotin deficiency, which was corrected by a return to the phenylalanine-restricted diet.⁴⁷