Abstract
Background: PKU patients on a strict low protein diet get most of their folic acid intake from protein substitute. Several protein substitutes contain high amounts of this vitamin. Concern has been raised about the safety of high levels of folic acid, especially in relation to cancer risk.
Methods: This cross-sectional study included 34 children and 22 adults with PKU. A dietary interview was performed and intake of folic acid and vitamin B12 from protein substitute was calculated for patients compliant with their protein substitute. Intakes of folic acid and vitamin B12 were compared with plasma levels of folate, vitamin B12, and homocysteine.
Results: Children aged 2–9 years had the highest intake of folic acid according to RDI (449 %), and children aged 7–10 years had the highest intake of folic acid according to UL (155 %). Median plasma folate level in PKU children was two times the upper reference level and in PKU adults well above. Children between 10 and 13 years had the highest level of plasma folate. Young children had both a high intake and high plasma levels of vitamin B12. Homocysteine levels were low or in the lower part of the normal reference range in most patients.
Conclusion: Children with PKU are at a particular risk of receiving folic acid high above RDI and many children with PKU receive doses above the UL. Many PKU patients have a very high level of plasma folate related to a very high content of folic acid in many of their protein substitutes.
Competing interests: None declared
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Acknowledgments
The authors would like to thank the National Neonatal Screening Unit for the analysis of serum phenylalanine. We would also like to thank Cathrine Åkre Strandskogen for help with revising the manuscript.
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Communicated by: Nenad Blau, PhD
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Take-Home Message
Several protein substitutes for PKU contain high levels of folic acid giving rise to intakes above European Tolerable Upper Intake Levels and high plasma folate levels. Children are at a particular risk.
Contributions of Individual Authors
Linn Helene Stølen: conception and design of the study, collection of data, analysis of data and interpretation of data, drafting the article
Rina Lilje: conception and design of the study, collection and interpretation of data, revision of the manuscript
Jens Veilemand Jørgensen: contributed in discussion of design, acquisition of data, and revision of the manuscript
Yngve Thomas Bliksrud: contributed in discussion of design, responsible for biochemical analyses, participated in writing and revision of the manuscript
Runar Almaas: conception and design of the study, interpretation of data, participated in writing and revision of manuscript
Guarantor: Linn Helene Stølen
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Conflict of Interest
Linn Helene Stølen has received travel grants/accommodation/meeting expenses from Nutricia and Vitaflo.
Rina Lilje has received travel grants/accommodation/meeting expenses from Nutricia and Vitaflo.
Jens V. Jørgensen has received travel grants/accommodation/meeting expenses from Nutricia.
Yngve Thomas Bliksrud has received travel grants/accommodation/meeting expenses from Nutricia.
Runar Almaas has received travel grants/accommodation/meeting expenses from Nutricia.
The project has been initiated and performed by the authors. Nutricia and Vitaflo have not been involved in the project neither with respect to initiation, funding, organization of the study, interpretation of data, nor writing of the paper. Nutricia and Vitaflo have not read the submitted paper.
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All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000. Informed consent was not required from the institutional review board at the time of the study, since the study included only routine data.
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Stølen, L.H., Lilje, R., Jørgensen, J.V., Bliksrud, Y.T., Almaas, R. (2013). High Dietary Folic Acid and High Plasma Folate in Children and Adults with Phenylketonuria. In: Zschocke, J., Gibson, K., Brown, G., Morava, E., Peters, V. (eds) JIMD Reports - Case and Research Reports, Volume 13. JIMD Reports, vol 13. Springer, Berlin, Heidelberg. https://doi.org/10.1007/8904_2013_260
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DOI: https://doi.org/10.1007/8904_2013_260
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