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Home > Living Well > Health Library > Phenylketonuria (Holistic)
Take a daily supplement containing 500 mg for every 8.8 pounds of body weight to prevent deficiencies caused by the PKU diet
Prevent vitamin and mineral deficiencies caused by the PKU diet by taking supplements that provide the daily value of L-tyrosine, vitamin K, vitamin B12, and selenium
Under a healthcare provider's supervision, improve mental functioning by adding amino acid supplements to each meal and at bedtime; take 150 mg per 2.2 pounds (1 kg) of body weight each of valine and isoleucine, and 200 mg per 2.2 pounds (1 kg) of body weight of leucine
Work with your healthcare provider and a nutritionist to maintain a phenylalanine-restricted diet that is nutritionally adequate
Help prevent increased phenylalanine intake by steering clear of soft drinks, candy, and other foods and drinks sweetened with aspartame (Nutrasweet)
Phenylketonuria (PKU) is a rare genetic disorder that results in excessive accumulation of the amino acid, phenylalanine, and reduced
levels of the amino acid, L-tyrosine, in the blood.1
If untreated, high levels of phenylalanine can cause severe mental retardation, behavioral disturbances,
and other brain and nerve problems. Fortunately, newborn screening programs now identify most cases of PKU in
the United States and other countries. Early diagnosis and treatment is the key to reducing or preventing
PKU-related conditions.2 Gene therapy is currently being researched as a possible cure.3, 4 Research
is also being conducted on methods to decrease levels of phenylalanine in the blood through the use of
certain enzymes5 and amino acids.6
Infants with PKU may be lethargic, feed poorly, and have a "mousy" odor from their sweat and urine. Eczema, sensitivity to sunlight, and light skin are also characteristic of PKU. Symptoms of children with untreated PKU include significantly diminished mental capacity, hyperactivity, and seizures.
Access to PKU resource/support groups, and education of family members may help simplify the complex dietary restrictions and improve one's ability to follow them.7, 8, 9
PKU during pregnancy (maternal PKU) is of particular concern. Excessively high or low levels of phenylalanine may occur during pregnancy, both of which may adversely affect the fetus.10 Maternal PKU can lead to fetal malformations, including small head size (microcephaly), heart abnormalities, failure to grow properly in the uterus (called intrauterine growth retardation), and mental retardation.11 Adverse effects on the offspring can be reduced and by careful dietary control both prior to and during pregnancy.12, 13, 14Consultation and follow-up visits with medical and nutritional specialists are necessary for effective monitoring and dietary guidance in people with PKU.
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. 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.
PKU can be controlled by a diet low in phenylalanine. The greatest benefits are achieved when the diet is started in the first few days of life, although later treatment will still help to reduce the severity of PKU-related conditions. Maintaining low phenylalanine levels through dietary control improves muscle control and behavioral and intellectual function.
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, this has not been found to be true in all studies. Therefore, more research is needed to resolve this issue. In a survey of 111 PKU treatment centers, 87% favored lifelong dietary restriction of phenylalanine.The 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. 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. 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.
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People with PKU may be deficient in several nutrients, due to the restricted diet which is low in protein and animal fat. Deficiencies of long-chain polyunsaturated fatty acids (LC-PUFAs),selenium,vitamin B12, and vitamin K may develop on this diet.
Selenium is important for normal antioxidant function. Research suggests that selenium deficiency and decreased antioxidant activity may contribute to the brain and nerve disorders associated with PKU. In two preliminary studies involving selenium-deficient people with PKU, supplementation with selenium in the form of sodium selenite corrected the deficiency, whereas supplementation with selenium in the form of selenomethionine did not.
Because the PKU diet is low in animal products, fat intake is also significantly reduced. The results of a preliminary study of children with PKU suggested that the low-fat PKU diet intake may impair the absorption of vitamin K, a fat-soluble vitamin, from the diet, possibly resulting in a vitamin K deficiency. In that study, children with PKU on a strict diet had low levels of certain vitamin K-dependent proteins needed for normal blood clotting.
1. Diamond A. Evidence for the importance of dopamine for prefrontal cortex functions early in life. Philos Trans R Soc Lond B Biol Sci 1996;351:1483-93 [review].
2. Cabalska MB, Nowaczewska I, Sendecka E, Zorska K. Longitudinal study on early diagnosis and treatment of phenylketonuria in Poland. Eur J Pediatr 1996;155 Suppl 1:S53-5.
3. Eisensmith RC, Woo SL. Gene therapy for phenylketonuria. Eur J Pediatr 1996;155 Suppl 1:S16-9 [review].
4. Lin CM, Tan Y, Lee YM, et al. Expression of human phenylalanine hydroxylase activity in T lymphocytes of classical phenylketonuria children by retroviral-mediated gene transfer. J Inherit Metab Dis 1997;20:742-54.
5. Sarkissian CN, Shao Z, Blain F, et al. A different approach to treatment of phenylketonuria: phenylalanine degradation with recombinant phenylalanine ammonia lyase. Proc Natl Acad Sci 1999;96:2339-44.
6. Pietz J, Kreis R, Rupp A, et al. Large neutral amino acids block phenylalanine transport into brain tissue in patients with phenylketonuria. J Clin Invest 1999;103:1169-78.
7. Waisbren SE, Rokni H, Bailey I, et al. Social factors and the meaning of food in adherence to medical diets: results of a maternal phenylketonuria summer camp. J Inherit Metab Dis 1997;20:21-7.
8. Scheibenreiter S, Tiefenthaler M, Hinteregger V, et al. Austrian report on longitudinal outcome in phenylketonuria. Eur J Pediatr 1996;155 Suppl 1:S45-9.
9. Weglage J, Funders B, Ullrich K, et al. Psychosocial aspects in phenylketonuria. Eur J Pediatr 1996;155 Suppl 1:S101-4.
10. Brenton DP, Lilburn M. Maternal phenylketonuria. A study from the United Kingdom. Eur J Pediatr 1996;155 Suppl 1:S177-80.
11. Levy HL, Ghavami M. Maternal phenylketonuria: a metabolic teratogen. Teratology 1996;53:176-84 [review].
12. Cechak P, Hejcmanova L, Rupp A. Long-term follow-up of patients treated for phenylketonuria (PKU). Results from the Prague PKU Center. Eur J Pediatr 1996;155 Suppl 1:S59-63.
13. Cipcic-Schmidt S, Trefz FK, Funders B, et al. German Maternal Phenylketonuria Study. Eur J Pediatr 1996;155 Suppl 1:S173-6.
14. Rouse B, Azen C, Koch R, et al. Maternal Phenylketonuria Collaborative Study (MPKUCS) offspring: facial anomalies, malformations, and early neurological sequelae. Am J Med Genet 1997;69:89-95.
Last Review: 06-08-2015
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