RANDOMIZED CONTROLLED TRIAL OF TYROSINE SUPPLEMENTATION ON NEUROPSYCHOLOGICAL PERFORMANCE IN PHENYLKETONURIA

Objective-To test the efficacy of tyrosine supplementation, as an adju nct to dietary treatment, on neuropsychological test performance in in dividuals with phenylketonuria. Design-A randomised controlled trial o f tyrosine supplementation using a double blind crossover procedure wi th three four week phases. Setting-The Hospital for Sick Children, Tor onto. Participants-21 individuals with phenylketonuria (ages 6 to 28 y ears, mean 11.3). Intervention-Participants were given 100 mg/kg body weight/d of L-tyrosine or L-alanine (placebo). Results-At baseline, pe rformance on several of the neuropsychological test measures was corre lated with tyrosine levels. Dietary supplements of tyrosine increased plasma tyrosine concentrations; however, no change in test performance was found across the tyrosine and placebo phases of the study, Conclu sions-Tyrosine supplementation of this type does not appear to alter n europsychological performance in individuals with phenylketonuria.