title: Moderately low vitamin B12 does not compromise transmethylation in adults on a free diet: implications for assessment of vitamin B12 status.
abstract: Lower reference limits for vitamin B12 are often defined solely in relation to haematological criteria. This may be misleading and there is evidence indicating that biochemical anomalies should also be considered. In 50 patients we measured creatine, as the major product of B12-mediated remethylation, to see if this helps the definition of the B12 reference interval and to investigate the possible effect of low B12 on essential transmethylation. Vitamin B12 values were grouped into six fractiles covering the range 50-500 ng/L; the corresponding creatine results were assessed by analysis of variance giving F = 0.94 and a significance of 0.466. Although no correlation between B12 and creatine was found, and therefore no obvious effect on transmethylation of low B12 concentration, this must be interpreted with respect to methionine availability. Other factors indicate that biochemical perturbations should be taken into account when defining vitamin B12 reference intervals.
authors.affiliation: Department of Clinical Biochemistry, University College of London Hospitals, at The National Hospital for Neurology and Neurosurgery, UK.
authors.forename: N
authors.initials: N
authors.lastname: Patel
authors.forename: A
authors.initials: A
authors.lastname: Briddon
mesh_terms: D000704:Analysis of Variance; D003401:Creatine / Q000097:blood*; D004044:Dietary Proteins; D006710:Homocysteine / Q000097:blood; D006801:Humans; D008715:Methionine / Q000097:blood; D008745:Methylation; D012016:Reference Values; D013223:Statistics as Topic; D014805:Vitamin B 12 / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004044:Dietary Proteins; D006710:Homocysteine; D008715:Methionine; D003401:Creatine; D014805:Vitamin B 12