title: Low vitamin B-12 concentrations in patients without anemia: the effect of folic acid fortification of grain.
abstract: BACKGROUND
  In some patients with vitamin B-12 deficiency mistakenly treated with folic acid, anemia resolved but neurologic complications became worse (masking). Fortification of enriched cereal grains with folic acid has raised concerns that people who consume large quantities of cereal grains, particularly the elderly, may be at increased risk of masking. It is unclear, however, what proportion of people with low vitamin B-12 concentrations do not have anemia and whether the proportion is increasing.
  
  
  OBJECTIVE
  We investigated whether fortification has increased the proportion of patients with low vitamin B-12 but without anemia.
  
  
  METHODS
  We reviewed the laboratory results of every patient for whom a vitamin B-12 concentration was measured at the Veterans Affairs Medical Center in Washington, DC, between 1992 and 2000. Those with a low vitamin B-12 concentration (< 258 pmol/L) had their hematocrits and mean cell volumes checked. The proportion without anemia was examined by year before, during, and after folic acid fortification began.
  
  
  RESULTS
  There were 1573 subjects with a low vitamin B-12 concentration. The proportion without anemia did not increase significantly from the prefortification period (39.2%) to the period of optional fortification (45.5%) and the postfortification period (37.6%). These findings did not change when the analysis was limited to patients aged > 60 y or when a more conservative definition of low vitamin B-12 (< 150 pmol/L) was used.
  
  
  CONCLUSIONS
  Despite evidence that folic acid exposure has increased dramatically since food fortification began, this population showed no evidence of an increase in low vitamin B-12 concentrations without anemia. If confirmed, these results would indicate that food fortification has not caused a major increase in masking of vitamin B-12 deficiency.
authors.affiliation: Division of Epidemiology, Statistics, and Prevention Research, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA. jamesmills@nih.gov
authors.forename: James L
authors.initials: JL
authors.lastname: Mills
authors.forename: Isabelle
authors.initials: I
authors.lastname: Von Kohorn
authors.forename: Mary R
authors.initials: MR
authors.lastname: Conley
authors.forename: Jack A
authors.initials: JA
authors.lastname: Zeller
authors.forename: Christopher
authors.initials: C
authors.lastname: Cox
authors.forename: Robert E
authors.initials: RE
authors.lastname: Williamson
authors.forename: D Robert
authors.initials: DR
authors.lastname: Dufour
mesh_terms: D000368:Aged; D000740:Anemia; D002523:Edible Grain; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage*; D005527:Food, Fortified; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D014806:Vitamin B 12 Deficiency / Q000453:epidemiology*
chemical_list: D005492:Folic Acid