title: Daily intake of 4 to 7 microg dietary vitamin B-12 is associated with steady concentrations of vitamin B-12-related biomarkers in a healthy young population.
abstract: BACKGROUND
  Studies have questioned whether the current Recommended Dietary Allowance (RDA) of 2.4 microg vitamin B-12/d is adequate.
  
  
  OBJECTIVE
  We examined the association between dietary vitamin B-12 intake and biomarkers of vitamin B-12 status.
  
  
  METHODS
  Dietary vitamin B-12 intake was estimated, and biomarkers of vitamin B-12 status were measured, in healthy men and women (n = 299; age range: 18-50 y) who were recruited from a Florida community. The National Cancer Institute Diet History Questionnaire was used. Plasma cobalamin, total transcobalamin, holo-transcobalamin, methylmalonic acid (MMA), total homocysteine (tHcy), and autoantibodies against intrinsic factor (IF) and Helicobacter pylori were analyzed in blood samples.
  
  
  RESULTS
  Antibodies to H. pylori were detected in 12% of subjects (35/299), and negative results for IF antibodies were obtained for all subjects. The intake of vitamin B-12 correlated significantly with cobalamin, holo-transcobalamin, MMA, and tHcy. Subjects were divided into quintiles on the basis of their dietary vitamin B-12 intake (range: 0.42-22.7 microg/d), and biomarkers of vitamin B-12 status were plotted against estimated dietary vitamin B-12 intake. All biomarkers appeared to level off at a daily dietary vitamin B-12 intake between 4.2 and 7.0 microg.
  
  
  CONCLUSIONS
  In persons with normal absorption, our data indicate that an intake of 4-7 microg vitamin B-12/d is associated with an adequate vitamin B-12 status, which suggests that the current RDA of 2.4 microg vitamin B-12/d might be inadequate for optimal biomarker status even in a healthy population between 18 and 50 y of age.
authors.affiliation: Department of Clinical Biochemistry, AS Aarhus University Hospital, Aarhus, Denmark. vakbor@yahoo.com
authors.forename: Mustafa Vakur
authors.initials: MV
authors.lastname: Bor
authors.forename: Kristina M
authors.initials: KM
authors.lastname: von Castel-Roberts
authors.forename: Gail Pa
authors.initials: GP
authors.lastname: Kauwell
authors.forename: Sally P
authors.initials: SP
authors.lastname: Stabler
authors.forename: Robert H
authors.initials: RH
authors.lastname: Allen
authors.forename: David R
authors.initials: DR
authors.lastname: Maneval
authors.forename: Lynn B
authors.initials: LB
authors.lastname: Bailey
authors.forename: Ebba
authors.initials: E
authors.lastname: Nexo
mesh_terms: D000293:Adolescent; D000328:Adult; D000907:Antibodies, Bacterial / Q000097:blood*; D001323:Autoantibodies / Q000097:blood; D015415:Biomarkers / Q000097:blood; D004032:Diet; D004305:Dose-Response Relationship, Drug; D005260:Female; D016480:Helicobacter pylori / Q000276:immunology; D006710:Homocysteine / Q000097:blood; D006801:Humans; D007437:Intrinsic Factor / Q000276:immunology; D008297:Male; D008764:Methylmalonic Acid / Q000097:blood; D008875:Middle Aged; D018673:Nutrition Policy; D009751:Nutritional Requirements; D009752:Nutritional Status; D012016:Reference Values; D014805:Vitamin B 12 / Q000008:administration & dosage* / Q000097:blood; D014803:Vitamin B Complex / Q000008:administration & dosage* / Q000097:blood; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial; D001323:Autoantibodies; D015415:Biomarkers; D006710:Homocysteine; D014803:Vitamin B Complex; D008764:Methylmalonic Acid; D007437:Intrinsic Factor; D014805:Vitamin B 12