title: Evidence from a Randomized Trial That Exposure to Supplemental Folic Acid at Recommended Levels during Pregnancy Does Not Lead to Increased Unmetabolized Folic Acid Concentrations in Maternal or Cord Blood.
abstract: BACKGROUND
  Exposure to higher intakes of folic acid (FA) from fortified foods and supplements, although largely considered beneficial, is associated with unmetabolized FA in the circulation, which has raised some health concerns.
  
  
  OBJECTIVE
  The effect of supplemental FA at a dose of 400 μg/d during pregnancy on unmetabolized FA concentrations in maternal plasma and newborn cord blood plasma was investigated.
  
  
  METHODS
  A new analysis was performed of blood samples from participants in a randomized trial in pregnancy. Women aged 18-35 y, who had taken 400 μg FA/d as recommended in the first trimester, were recruited at the start of trimester 2 and randomly allocated to receive either 400 μg FA/d (n = 59) or a placebo (n = 67) throughout the second and third trimesters until delivery. Unmetabolized FA concentrations in maternal and cord blood samples were measured by LC-tandem MS analysis.
  
  
  RESULTS
  In response to the intervention from gestational week 14 through delivery, a higher proportion of women in the FA compared with the placebo group had detectable FA (≥0.27 nmol/L) in plasma, but the difference in concentrations was not statistically significant (mean ± SD: 0.44 ± 0.80 compared with 0.13 ± 0.49 nmol/L, P = 0.38). FA treatment throughout pregnancy resulted in higher cord blood plasma total folate (50.6 ± 20.1 compared with 34.5 ± 14.4 nmol/L; P = 0.004) and 5-methyltetrahydrofolate (50.4 ± 20.3 compared with 34.5 ± 14.4 nmol/L; P = 0.005) concentrations, but FA was detected only in 8 of 53 available cord blood samples, and the proportion of samples with detectable FA concentrations was similar in FA-treated and placebo groups.
  
  
  CONCLUSIONS
  Plasma concentrations of unmetabolized FA arising from supplemental FA at a dose of 400 μg/d, in addition to FA from fortified foods, were low or undetectable in mothers and newborns. The benefits for mothers and offspring of continuing FA supplementation beyond the first trimester of pregnancy can be achieved without posing any risk of increasing unmetabolized circulating FA, even in those already exposed to FA from fortified foods.
authors.affiliation: Northern Ireland Centre for Food & Health (NICHE), School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland; k.pentieva@ulster.ac.uk.
authors.forename: Kristina
authors.identifier: http://orcid.org/0000-0003-2059-534X
authors.initials: K
authors.lastname: Pentieva
authors.affiliation: Vitamin Metabolism and Aging Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA;
authors.forename: Jacob
authors.initials: J
authors.lastname: Selhub
authors.affiliation: Vitamin Metabolism and Aging Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA;
authors.forename: Ligi
authors.initials: L
authors.lastname: Paul
authors.affiliation: School of Medicine and.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Molloy
authors.affiliation: School of Agriculture & Food Science, University College Dublin, Dublin, Ireland;
authors.forename: Breige
authors.initials: B
authors.lastname: McNulty
authors.affiliation: Northern Ireland Centre for Food & Health (NICHE), School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland;
authors.forename: Mary
authors.identifier: http://orcid.org/0000-0001-6470-1728
authors.initials: M
authors.lastname: Ward
authors.affiliation: Causeway Hospital, The Northern Health and Social Care Trust, Coleraine, Northern Ireland;
authors.forename: Barry
authors.initials: B
authors.lastname: Marshall
authors.affiliation: Royal-Jubilee Maternity Service, Belfast, Northern Ireland;
authors.forename: James
authors.identifier: http://orcid.org/0000-0001-6862-8556
authors.initials: J
authors.lastname: Dornan
authors.affiliation: Northern Ireland Centre for Food & Health (NICHE), School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland;
authors.forename: Rosie
authors.initials: R
authors.lastname: Reilly
authors.affiliation: School of Biotechnology, Dublin City University, Dublin, Ireland; and.
authors.forename: Anne
authors.initials: A
authors.lastname: Parle-McDermott
authors.affiliation: Frontier Science (Scotland), Kincraig, Scotland.
authors.forename: Ian
authors.initials: I
authors.lastname: Bradbury
authors.affiliation: School of Biotechnology, Dublin City University, Dublin, Ireland; and.
authors.forename: Mari
authors.initials: M
authors.lastname: Ozaki
authors.affiliation: School of Biochemistry and Immunology, Trinity College, Dublin, Ireland;
authors.forename: John M
authors.initials: JM
authors.lastname: Scott
authors.affiliation: Northern Ireland Centre for Food & Health (NICHE), School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland;
authors.forename: Helene
authors.initials: H
authors.lastname: McNulty
mesh_terms: D000293:Adolescent; D000328:Adult; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D005260:Female; D005312:Fetal Blood / Q000737:chemistry*; D005492:Folic Acid / Q000008:administration & dosage* / Q000097:blood* / Q000378:metabolism; D005527:Food, Fortified; D006801:Humans; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000097:blood; D011110:Polymorphism, Genetic; D011247:Pregnancy; D055815:Young Adult
chemical_list: D005492:Folic Acid; C573423:MTHFR protein, human; D042965:Methylenetetrahydrofolate Reductase (NADPH2)
keywords: folic acid fortified foods; folic acid supplementation; maternal and cord blood; plasma; pregnancy; unmetabolized folic acid and total folate