Abstract
Accumulating evidence suggests that hyperphenylalaninemia in phenylketonuria (PKU) can cause neuropsychological and psychosocial problems in diet-off adult patients, and that such symptoms improve after resumption of phenylalanine-restricted diet, indicating the need for lifetime low-phenylalanine diet. While limiting protein intake, dietary therapy should provide adequate daily intake of energy, carbohydrates, fat, vitamins, and microelements. We evaluated nutrient balance in 14 patients with classical PKU aged 4–38years. Approximately 80–85% of the recommended dietary allowance (RDA) of protein in Japanese was supplied through phenylalanine-free (Phe-free) milk and Phe-free amino acid substitutes. Nutritional evaluation showed that the calorie and protein intakes were equivalent to the RDA. Phenylalanine intake was 9.8±2.2mg/kg of body weight/day, which maintained normal blood phenylalanine concentration by the 80% Phe-free protein rule. The protein, fat, and carbohydrate ratio was 9.5:23.9:66.6% with relative carbohydrate excess. Phe-free milk and amino acid substitutes provided 33.7% of carbohydrate, 82.1% of protein, and 66.7% of fat intake in all. Selenium and biotin intakes were 25.0% and 18.1% of the RDA and adequate intake (AI) for Japanese, respectively; both were not included in Phe-free milk. PKU patients showed low serum selenium, low urinary biotin, and high urinary 3-hydroxyisovaleric acid in this study. The intakes of magnesium, zinc, and iodine were low (71.5%, 79.5%, and 71.0% of the RDA, respectively) and that of phosphorus was 79.7% of the AI, although they were supplemented in Phe-free milk. PKU patients depend on Phe-free milk and substitutes for daily requirement of microelements and vitamins as well as protein and fat. Development of low-protein food makes it possible to achieve the aimed phenylalanine blood level, but this lowers the intake of microelements and vitamins from natural foods. The dietary habits vary continuously with age and environment in PKU patients. We recommend the addition of selenium and biotin to Phe-free milk in Japan and the need to review the composition of microelements and vitamins in A-1 and MP-11 preparations.
Highlights
Phenylketonuria (PKU) is an autosomal recessive disorder caused by deficiency in hepatic phenylalanine hydroxylase and is usually diagnosed early in life
We demonstrate that 80 to 85% of daily protein intake should be from Phe-free milk, A-1, and MP-11 in PKU patients
Six PKU patients aged b 10 years could be treated with Phe-free milk alone
Summary
Phenylketonuria (PKU) is an autosomal recessive disorder caused by deficiency in hepatic phenylalanine hydroxylase and is usually diagnosed early in life. Unless the affected child is maintained on a strict low-phenylalanine diet, PKU leads to mental retardation, seizures, behavioral difficulties, and other neurological symptoms [1]. Restriction of phenylalanine intake was thought to be necessary for brain development in infants and children with PKU. Accumulating evidence in the last several years suggested that hyperphenylalaninemia can cause neuropsychological and psychosocial problems in diet-off adults, and that such symptoms improved after resumption of phenylalanine-restricted diet [2,3,4,5]. Diet therapy is necessary and important over the lifetime of patients with PKU. PKU patients and intake of Phe-free milk and A-1/MP-11 in the nutritional evaluation.
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