title: Folate absorption in women with a history of neural tube defect-affected pregnancy.
abstract: BACKGROUND
  The risk of neural tube defects (NTDs) is significantly reduced by supplemental folic acid. NTD risk may be associated with impaired absorption of polyglutamyl folate, the primary form of naturally occurring food folate, and of folic acid in supplements or fortified food. Stable-isotope methods provide the specificity needed to test this hypothesis.
  
  
  OBJECTIVE
  We determined whether women who had an NTD-affected pregnancy had a reduced ability compared with control women to absorb polyglutamyl folate relative to folic acid.
  
  
  METHODS
  Healthy, nonpregnant women with a history of an NTD-affected pregnancy (cases; n = 11) and control women (n = 11) were administered an oral dose containing a mixture of [(2)H]pteroylpentaglutamate ([(2)H(2)]PteGlu(5); 233 nmol) and [(13)C]pteroylmonoglutamate ([(13)C(5)]PteGlu(1); 567 nmol) after a 30-d saturation protocol (2 mg unlabeled folic acid/d). Relative extents of absorption were evaluated by urinary excretion of (2)H(2)- and (13)C(5)-labeled folates 48 h postdose.
  
  
  RESULTS
  During the first 24 h postdose, cases excreted less (f1.gif" BORDER="0"> +/- SD) [(2)H(2)]PteGlu(5) (21 +/- 12% compared with 37 +/- 19%; P = 0.01) and [(13)C(5)]PteGlu(1) (17 +/- 8% compared with 31 +/- 14%; P = 0.007) than did controls. No significant differences between cases and controls were detected in the percentage of [(2)H(2)]PteGlu(5) or [(13)C(5)]PteGlu(1) excreted during the second 24 h postdose or when the data were averaged over 48 h. However, excretion of the [(2)H(2)]folates tended to be lower in cases than in controls over the 48-h period (33 +/- 13% compared with 45 +/- 26%; P = 0.21). A similar trend (P = 0.29) for lower excretion of [(13)C(5)]folates in cases was also observed (31 +/- 16% compared with 39 +/- 17%). The ratio of urinary [(2)H(2)]folates to [(13)C(5)]folates did not differ significantly between cases and controls.
  
  
  CONCLUSIONS
  These data suggest the need for a larger-scale study using stable-isotope methods to further investigate this hypothesis.
authors.affiliation: Department of Food Science and Human Nutrition, College of Agriculture, University of Florida, Gainesville, FL 32611, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Boddie
authors.forename: E R
authors.initials: ER
authors.lastname: Dedlow
authors.forename: J A
authors.initials: JA
authors.lastname: Nackashi
authors.forename: F J
authors.initials: FJ
authors.lastname: Opalko
authors.forename: G P
authors.initials: GP
authors.lastname: Kauwell
authors.forename: J F
authors.initials: JF
authors.lastname: Gregory
authors.forename: L B
authors.initials: LB
authors.lastname: Bailey
mesh_terms: D000284:Administration, Oral; D000328:Adult; D002247:Carbon Isotopes; D016022:Case-Control Studies; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D006801:Humans; D007408:Intestinal Absorption / Q000502:physiology*; D009436:Neural Tube Defects / Q000517:prevention & control*; D011624:Pteroylpolyglutamic Acids / Q000493:pharmacokinetics / Q000652:urine
chemical_list: D002247:Carbon Isotopes; D011624:Pteroylpolyglutamic Acids; D005492:Folic Acid