title: A daily intake of approximately 6 microg vitamin B-12 appears to saturate all the vitamin B-12-related variables in Danish postmenopausal women.
abstract: BACKGROUND
  Recommended daily intakes of vitamin B-12 vary between 2 and 6 microg.
  
  
  OBJECTIVE
  The objective was to examine the associations between vitamin B-12 intake and markers of vitamin B-12 deficiency.
  
  
  METHODS
  We studied 98 Danish postmenopausal women aged 41-75 y. Serum cobalamin, transcobalamin (TC) saturated with vitamin B-12 (holo-TC), TC saturation (holo-TC/total TC), methylmalonic acid (MMA), and total homocysteine (tHcy) were measured to assess vitamin B-12 status. Dietary intakes of vitamin B-12 were determined from 7-d weighed food records. Gastric pH measurement and the alkali-challenge test were performed with the use of Heidelberg radiotelemetric capsules.
  
  
  RESULTS
  The total intake of vitamin B-12 ranged from 1.2 to 23.9 microg/d. All vitamin B-12-related variables, except gastric pH, correlated significantly with total vitamin B-12 intake. Those taking supplements (54%) had higher circulating concentrations of cobalamin and TC saturation and lower concentrations of MMA and tHcy than did those not taking supplements. All subjects were divided into quintiles according to their total vitamin B-12 intake. For all the variables analyzed, the curves appeared to level off at a daily vitamin B-12 intake of approximately 6 microg; the median (and 25th-75th percentiles) for cobalamin was 380 (270-480) pmol/L, for holo-TC was 119 (92-162) pmol/L, for MMA was 0.12 (0.14-0.17) micromol/L, and for tHcy was 9.75 (8.3-11.40) micromol/L (n = 58).
  
  
  CONCLUSIONS
  A daily vitamin B-12 intake of 6 microg appeared to be sufficient to correct all the vitamin B-12-related variables measured in the postmenopausal Danish women in this study.
authors.affiliation: Department of Clinical Biochemistry, Nørrebrogade Section, Aarhus Hospital, Aarhus, Denmark. vakurbor@hotmail.com
authors.forename: Mustafa Vakur
authors.initials: MV
authors.lastname: Bor
authors.forename: Eva
authors.initials: E
authors.lastname: Lydeking-Olsen
authors.forename: Jan
authors.initials: J
authors.lastname: Møller
authors.forename: Ebba
authors.initials: E
authors.lastname: Nexø
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000368:Aged; D003718:Denmark; D004032:Diet; D015930:Diet Records; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D005260:Female; D006710:Homocysteine / Q000097:blood; D006801:Humans; D008764:Methylmalonic Acid / Q000097:blood; D008875:Middle Aged; D009752:Nutritional Status; D017698:Postmenopause / Q000097:blood / Q000378:metabolism*; D018709:Statistics, Nonparametric; D014155:Transcobalamins / Q000378:metabolism; D014805:Vitamin B 12 / Q000008:administration & dosage* / Q000097:blood* / Q000378:metabolism; D014806:Vitamin B 12 Deficiency / Q000097:blood* / Q000517:prevention & control; D014803:Vitamin B Complex / Q000008:administration & dosage* / Q000097:blood / Q000378:metabolism
chemical_list: D014155:Transcobalamins; D006710:Homocysteine; D014803:Vitamin B Complex; D008764:Methylmalonic Acid; D014805:Vitamin B 12