Phenylketonuria is a common amino acid metabolic disorder. It primarily occurs because the patient's liver lacks phenylalanine hydroxylase, leading to the inability of phenylalanine to convert into tyrosine. This causes phenylalanine to accumulate in large amounts in the body, and it cannot be excreted through urine, presenting some corresponding clinical symptoms. The diet for phenylketonuria mainly involves avoiding high-protein foods, such as dairy, eggs, and soy products. Additionally, spicy, raw, and greasy foods should be avoided as they can negatively impact the health of the child. It is also beneficial to include starch-rich foods in the diet, such as potato starch, vermicelli, pumpkin, and Chinese yam, as these foods are low in phenylalanine and high in carbohydrates. Furthermore, vitamin C can be consumed without restrictions in cases of phenylketonuria, and it should be taken in moderation.