title: Folic acid source, usual intake, and folate and vitamin B-12 status in US adults: National Health and Nutrition Examination Survey (NHANES) 2003-2006.
abstract: BACKGROUND
  US adults have access to multiple sources of folic acid. The contribution of these sources to usual intakes above the tolerable upper intake level (UL) (1000 microg/d) and to folate and vitamin B-12 status is unknown.
  
  
  OBJECTIVE
  The objective was to estimate usual folic acid intake above the UL and adjusted serum and red blood cell folate, vitamin B-12, methylmalonic acid, and homocysteine concentrations among US adults by 3 major folic acid intake sources-enriched cereal-grain products (ECGP), ready-to-eat cereals (RTE), and supplements (SUP)-categorized into 4 mutually exclusive consumption groups.
  
  
  METHODS
  We used data from the National Health and Nutrition Examination Survey (NHANES) 2003-2006 (n = 8258).
  
  
  RESULTS
  Overall, 2.7% (95% CI: 1.9%, 3.5%) of adults consumed more than the UL of folic acid. The proportions of those who consumed folic acid from ECGP only, ECGP+RTE, ECGP+SUP, and ECGP+RTE+SUP were 42%, 18%, 25%, and 15%, respectively. Of 60% of adults who did not consume supplements containing folic acid (ECGP only and ECGP+RTE), 0% had intakes that exceeded the UL. Of 34% and 6% of adults who consumed supplements with an average of < or = 400 and >400 microg folic acid/d, <1% and 47.8% (95% CI: 39.6%, 56.0%), respectively, had intakes that exceeded the UL. Consumption of RTE and/or supplements with folic acid was associated with higher folate and vitamin B-12 and lower homocysteine concentrations, and consumption of supplements with vitamin B-12 was associated with lower methylmalonic acid concentrations (P < 0.001).
  
  
  CONCLUSIONS
  At current fortification levels, US adults who do not consume supplements or who consume an average of < or =400 microg folic acid/d from supplements are unlikely to exceed the UL in intake for folic acid.
authors.affiliation: Office of Public Health Genomics, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. qay0@cdc.gov
authors.forename: Quanhe
authors.initials: Q
authors.lastname: Yang
authors.forename: Mary E
authors.initials: ME
authors.lastname: Cogswell
authors.forename: Heather C
authors.initials: HC
authors.lastname: Hamner
authors.forename: Alicia
authors.initials: A
authors.lastname: Carriquiry
authors.forename: Lynn B
authors.initials: LB
authors.lastname: Bailey
authors.forename: Christine M
authors.initials: CM
authors.lastname: Pfeiffer
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Berry
mesh_terms: D000328:Adult; D000368:Aged; D003710:Demography; D004032:Diet; D019587:Dietary Supplements; D002149:Energy Intake; D005006:Ethnicity; D005260:Female; D005492:Folic Acid / Q000097:blood* / Q000378:metabolism*; D006306:Health Surveys; D006710:Homocysteine / Q000097:blood; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008568:Memory; D008875:Middle Aged; D009749:Nutrition Surveys; D044469:Racial Groups; D014481:United States; D014805:Vitamin B 12 / Q000097:blood*; D055815:Young Adult
chemical_list: D006710:Homocysteine; D005492:Folic Acid; D014805:Vitamin B 12