Nutritional Consequences of Adhering to a Low Phenylalanine Diet for Late-Treated Adults with PKU : Low Phe Diet for Adults with PKU.

BACKGROUND: The main treatment for phenylketonuria (PKU) is a low phenylalanine (Phe) diet, phenylalanine-free protein substitute and low-protein special foods. This study describes dietary composition and nutritional status in late-diagnosed adult patients adhering to a PKU diet. METHODS: Nineteen patients, followed at Oslo University Hospital in Norway, participated; median age was 48 years (range 26-66). Subjects were mild to severely mentally retarded. Food intake, clinical data and blood analyses relevant for nutritional status were assessed. RESULTS: Median energy intake was 2,091 kcal/day (range 1,537-3,277 kcal/day). Carbohydrates constituted 59% (range 53-70%) of the total energy, including 15% from added sugar; 26% was from fat. The total protein intake was 1.02 g/kg/day (range 0.32-1.36 g/kg/day), including 0.74 g/kg/day (range 0.13-1.07 g/kg/day) from protein substitutes. Median dietary Phe intake was 746 mg/day (range 370-1,370 mg/day). Median serum Phe was 542 µmol/L (range 146-1,310 mg/day). Fortified protein substitutes supplied the main source of micronutrients. Iron intake was 39.5 mg/day (range 24.6-57 mg/day), exceeding the upper safe intake level. Intake of folate and folic acid, calculated as dietary folate equivalents, was 1,370 µg/day (range 347-1744 µg/day), and resulted in high blood folate concentrations. Median intake of vitamin B(12) was 7.0 µg/day (range 0.9-15.1 µg/day). CONCLUSIONS: The diet supplied adequate protein and energy. Fortification of the protein substitutes resulted in excess intake of micronutrients. The protein substitutes may require adjustment to meet nutritional recommendations for adults with PKU.

Optimising growth in phenylketonuria: current state of the clinical evidence base.

Patients with phenylketonuria (PKU) must follow a strict low-phenylalanine (Phe) diet in order to minimise the potentially disabling neuropsychological sequelae of the disorder. Research in this area has unsurprisingly focussed largely on managing blood Phe concentrations to protect the brain. Protein requirements in dietary management of PKU are met mostly from Phe-free protein substitutes with the intake of natural protein restricted to patient tolerance. Several reports have suggested that growth in early childhood in PKU is sub-optimal, relative to non-PKU control groups or reference populations. We reviewed the literature searching for evidence regarding PKU and growth as well as possible links between dietary management of PKU and growth. The search retrieved only limited evidence on the effect of PKU and its dietary management on growth. Physical development in PKU remains an under-studied aspect of this disorder.

Adjusting diet with sapropterin in phenylketonuria: what factors should be considered?

The usual treatment for phenylketonuria (PKU) is a phenylalanine-restricted diet. Following this diet is challenging, and long-term adherence (and hence metabolic control) is commonly poor. Patients with PKU (usually, but not exclusively, with a relatively mild form of the disorder) who are responsive to treatment with pharmacological doses of tetrahydrobiopterin (BH4) have either lower concentrations of blood phenylalanine or improved dietary phenylalanine tolerance. The availability of a registered formulation of BH4 (sapropterin dihydrochloride, Kuvan®) has raised many practical issues and new questions in the dietary management of these patients. Initially, patients and carers must understand clearly the likely benefits (and limitations) of sapropterin therapy. A minority of patients who respond to sapropterin are able to discontinue the phenylalanine-restricted diet completely, while others are able to relax the diet to some extent. Care is required when altering the phenylalanine-restricted diet, as this may have unintended nutritional consequences and must be undertaken with caution. New clinical protocols are required for managing any dietary change while maintaining control of blood phenylalanine, ensuring adequate nutrition and preventing nutritional deficiencies, overweight or obesity. An accurate initial evaluation of pre-sapropterin phenylalanine tolerance is essential, and the desired outcome from treatment with sapropterin (e.g. reduction in blood phenylalanine or relaxation in diet) must also be understood by the patient and carers from the outset. Continuing education and support will be required thereafter, with further adjustment of diet and sapropterin dosage as a young patient grows.

Dietary management practices in phenylketonuria across European centres.

BACKGROUND: Dietary phenylalanine restriction is the cornerstone of phenylketonuria (PKU) management. However, there are no European consensus guidelines for its optimal dietary care. METHODS: Detailed information on the routine dietary management of PKU was obtained from 10 European centres using structured questionnaires. Each centre was represented by one dietitian/nutritionist or physician (European Nutritionist Expert Panel). RESULTS: All centres screened for PKU within the first 10 days of life. PKU prevalence was highest in Turkey. The training, roles and responsibilities of dietitians and nutritionists varied widely; in some centres dietitians were responsible for managing the diet, while in others this was performed by a physician. There were marked differences in target blood phenylalanine concentrations, the dosages of protein substitutes, systems for allocating daily phenylalanine allowance, and the definition of foods that could be eaten without restriction ('free foods'). Eighty percent (n=8/10) of centres encouraged breastfeeding together with protein substitute in infants with PKU. CONCLUSIONS: Important differences exist among centres across Europe in the dietary management of PKU, and in support systems designed to assist patients in managing their diets. Further studies are needed to compare different dietary treatments with the aim of identifying best practice to optimise phenylalanine control and dietary adherence.