Are there effective alternative therapies for pku?

No: The only way to treat pku or rather to prevent symptoms of this disease is proper diet eliminating certain aminoacids from the diet. To prevent malnutrition you need to discuss this diet with specialist in metabolic diseases and dietitian.

Diet: Treatment for pku is based on diet. There are no 'natural' remedies. Treatment involves a diet that is extremely low in phenylalanine, particularly when the child is growing. The diet must be strictly followed.

No: I am not sure I understand your question. If you neglect the special PKU diet, your child will pay for your mistake by getting permanent brain damage. Anyone telling you otherwise is your worst enemy. There are a variety of complementary treatments that have been offered for brain-damaged children from whatever cause; I can't address whether any of them work. Please be careful.