EFFECT OF GRADUAL LIBERALIZATION OF DIET ON COGNITIVE FUNCTIONS AND BEHAVIOR IN PKU

Abstract

The question of if, when and how dietary therapy can be stopped in PKU patients is still controversial. A gradual increase in natural protein was introduced with the aim to stop dietary liberalization when the serum Phe exceeded 20 mg/100 ml. Twenty three patients aged 10 - 14 years with classical PKU (serum Phe > 20 mg/100 ml) were studied with WISC, neuropsychological tests and standard questionnaires to parents and teachers before and 3 (2) years after liberalization of diet. About one fifth of the patients could normalize the diet completely, one fifth tolerated only a small increase in natural protein while the rest fell in between these two extremes. The compliance was good in all but two. There were no significant changes in IQ, neuropsychological tests or in behavior problems during the observation period. The data suggest that a gradual increase in natural protein may disclose patients at risk, and that serum Phe levels below 20 mg/100 do not harm cognitive functions or cause behavioral problems in PKU teenagers.