Dietary Management of Phenylketonuria

Phenylketonuria (PKU) is the most prevalent inborn error of amino acid metabolism in newborns. Complete or partial enzyme deficiency causes accumulation of phenylalanine (Phe) and its metabolites in blood and if left untreated causing detrimental effects on brain development and function.Lifelong low-Phe diet is the mainstay of treatment. Complete adherence to diet leads to blood level Phe control between 120–360 μmol/L for individuals aged 0–12 years and for maternal PKU, and 120–600 μmol/L for non-pregnant individuals older than 12 years.Dietary treatment consists of a severe restriction of dietary Phe; replacement of non-Phe amino acids with a protein substitute commonly supplemented with essential fatty acids and other micronutrients combined with low-protein foods from fruits, some vegetables, sugars, fats and oil and special low-protein foods.The quality and composition of the diet is scheduled according to gender, age, weight, enzyme deficiency level. For each patient energy, protein, Phe, tyrosine and water requirements should measure individually.In infancy and early childhood, phe-free AA formula provides most of the protein, energy and nutrient needs for growth. Dietary phe requirements are met by small amounts of breast milk or infant formula in this age. As feeding skills develop, phe requirements are met through small amounts of rice cereal, fruits and vegetables. Frequent consumption of AA formula throughout the day results in stable plasma phe concentrations and higher phe tolerance as protein retention and synthesis improve in adulescence.Nutritional, clinical, and biochemical follow-up is necessary for all patients, regardless of therapy.