ABSTRACT
Abstract Phenylketonuria (PKU) is caused by a deficient activity of enzyme phenylalanine (Phe) hydroxylase, which results in high Phe blood concentration, which is toxic to the central nervous system. The fundamental purpose of nutritional treatment is to reduce and maintain blood Phe between 2 mg/dL (120 µmol/L) and 6 mg/dL (360 µmol/L) in order to prevent neuropathogenic complications. At the same time, nutrition support must provide enough energy and nutrients to promote normal growth and development and also to avoid vitamin and mineral deficiencies. Phenylketonuria treatment must be maintained long-life and its adherence must be frequently assessed. The amount of Phe required by patients with PKU varies throughout life and must be adjusted according to individual tolerance, residual phenylalanine hydroxylase enzymatic activity, age, sex, growth rate, protein intake, and nutritional and biochemical status among others. Treatment must be done by trained personnel. It is necessary to unify treatment criteria and further research must be done.