Patients with phenylketonuria usually eat low-phenylalanine foods, and foods that contain a lot of phenylalanine should be consumed in small amounts. In young children, low-phenylalanine formula is the main treatment. When the blood phenylalanine concentration is reduced to the ideal concentration, natural diet can be added gradually in small amounts, of which breast milk is preferred because the blood phenylalanine content of breast milk is only 1/3 of that of cow’s milk. Foods high in protein, such as meat, eggs and milk, nuts, seafood, beans and legumes, contain high levels of phenylalanine and should only be consumed in small amounts. Phenylalanine-free foods and low-phenylalanine foods, which are fundamental to the diet of people with phenylketonuria, make up the majority of daily dietary intake. Low-phenylalanine foods include fruits and most vegetables, among others. Dietary advice for people with phenylalanine is to follow your doctor’s instructions and seek medical attention if you are unwell.