title: Adult patients with well-controlled phenylketonuria tolerate incidental additional intake of phenylalanine.
abstract: OBJECTIVE
  In patients with phenylketonuria (PKU), target ranges of blood phenylalanine (Phe) concentrations have been tightened in order to improve long-term outcomes. We investigated day-to-day and week-to-week variations in blood Phe concentration and the effect of an additional Phe load.
  
  
  METHODS
  We performed a longitudinal study in 6 adult PKU patients. The study was divided in five 7-day periods: 1 period without any intervention (period I) and 4 periods with a Phe load on day 3 equivalent to 100% (periods II and III) and to 200% (periods IV and V) of each patient's individual daily Phe intake. Phe loading was given as encapsulated L-Phe. Blood spots to measure blood Phe concentration were taken each morning before breakfast in all periods.
  
  
  RESULTS
  Day-to-day and week-to-week blood Phe concentrations varied considerably with and without intervention in Phe intake. Equal loads of Phe did not result in comparable effects in blood Phe concentrations in all patients. In periods II-IV, mean blood Phe concentrations of days 1-3 (pre-load) were not significantly different from days 4-7 (post-load). The 200% load resulted in a significantly larger variation.
  
  
  CONCLUSIONS
  These results showed that patients with well-controlled PKU can incidentally tolerate 100% - and in some cases 200% - of their normal daily Phe intake.
authors.affiliation: Section of Metabolic Diseases, Beatrix Children's Hospital, University Medical Centre of Groningen, University of Groningen, Groningen, The Netherlands. G.van.Rijn@fd.umcg.nl
authors.forename: Margreet
authors.initials: M
authors.lastname: van Rijn
authors.forename: Marieke
authors.initials: M
authors.lastname: Hoeksma
authors.forename: Pieter J J
authors.initials: PJ
authors.lastname: Sauer
authors.forename: Pim
authors.initials: P
authors.lastname: Modderman
authors.forename: Dirk-Jan
authors.initials: DJ
authors.lastname: Reijngoud
authors.forename: Francjan J
authors.initials: FJ
authors.lastname: van Spronsen
mesh_terms: D000293:Adolescent; D000328:Adult; D000596:Amino Acids / Q000627:therapeutic use; D002214:Capsules; D015930:Diet Records; D019587:Dietary Supplements; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D010349:Patient Compliance; D010649:Phenylalanine / Q000008:administration & dosage* / Q000009:adverse effects* / Q000097:blood; D010661:Phenylketonurias / Q000097:blood / Q000178:diet therapy*; D017410:Practice Guidelines as Topic; D013997:Time Factors; D055815:Young Adult
chemical_list: D000596:Amino Acids; D002214:Capsules; D010649:Phenylalanine