today, scientists know what foods have phenylalanine in them, and they have created a special diet for people with pku. since they cannot use it, people with pku cannot eat foods that have a lot of phenylalanine, like eggs, meat and milk. an artificial sweetener called aspartame is also a source of phenylalanine. people with pku take a lot of vitamins to make up for the foods they cannot eat, especially vitamins b6 and b12.