Fundamental to an understanding of the dietary treatment of PKU is a comprehension of normal nutritional requirements in health. Published recommended daily dietary allowances give a guide to the macro and micro nutrient requirements for normal healthy children and with the use of food composition data, diets can be constructed to meet these requirements.
For individuals with a genetic defect affecting metabolism, dietary allowances and food composition data can be used to manipulate the dietary intake to limit the consumption of affected nutrients, for example phenylalanine in the case of PKU, while meeting nutritional needs for normal growth and development. Special diets of this complexity are usually designed by a paediatric dietitian.
Such diets need to take into account other genetic, social and environmental influences on food intake and the recommendations for different types of food needed at various ages.