[High plasma folate in patients with phenylketonuria].

Unlabelled: Phenylketonuria is an inborn error of metabolism treated with a closely monitored low phenylalanine diet. Protein substitutes used for treatment are supplemented with vitamins and micronutrients.

Aim: The aim of this study was to investigate plasma folic acid concentrations in children with phenylketonuria.

Materials And Methods: Retrospective analysis of medical records of 73 patients with phenylketonuria and 28 with mild hyperphenylalaninemia (on normal diet) was carried out. Intake of folic acid was calculated on the basis of protein substitute intake. Folate concentrations were analyzed according to their intake, and concentration of homocysteine and phenylalanine.

Results: In 76.7% patients with phenylketonuria intake of folic acid exceeded recommended dietary allowance. Serum folic acid concentrations above upper reference level were detected in 75.3% patients with phenylketonuria and only in 25% patients with hyperphenylalaninemia (p<0.0001). Strong positive correlation between daily intake of folic acid (with protein substitute) and concentration plasma folic acid (corr=0.55, p<0.0001) has been observed.

Conclusions: Low phenylalanine diet using protein substitutes currently available in Poland predisposes to high concentration of plasma folic acid. The security of folic acid hipersupplementation in patients with phenylketonuria requires further detailed research.