Protein recommendations are adjusted for the protein source. The results of dietary therapy in children with PKU are impressive. While discontinuation of dietary therapy by the age of six to 10 years was once considered safe, this approach is no longer advocated. Although most PKU clinics recommend treatment into adulthood, some patients may prematurely discontinue the dietary restrictions. Phenylalanine-restricted diets are difficult to administer and maintain, especially during adolescence.
Adherence is understandably difficult, and teenagers sometimes resist treatment.
In other cases, physicians operating under earlier treatment recommendations may prematurely discontinue therapy. Their mean IQ on the Wechsler Adult Intelligence Scale was 83, probably because some were not identified on newborn screening and did not receive the benefit of early intervention and because the majority had discontinued dietary therapy between six to 10 years of age. Women with a history of PKU must continue dietary therapy during pregnancy to prevent fetal damage. With current awareness of the need to adhere to dietary therapy during pregnancy, women are more likely to continue treatment. 5,14 Adults who have severe mutations in the phenylalanine hydroxylase gene should definitely remain on dietary therapy for life.