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Vitamin B 12

Smith, A. David and Warren, Martin J. and Refsum, Helga (2018) Vitamin B 12. In: Eskin, N.A. Michael, ed. New Research and Developments of Water-Soluble Vitamins. Advances in Food and Nutrition Research . Elsevier, pp. 215-279. ISBN 978-0-12-811803-0. (doi:10.1016/bs.afnr.2017.11.005) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided) (KAR id:66524)

The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided. (Contact us about this Publication)
Official URL
https://doi.org/10.1016/bs.afnr.2017.11.005

Abstract

The biosynthesis of B12, involving up to 30 different enzyme-mediated steps, only occurs in bacteria. Thus, most eukaryotes require an external source of B12, and yet the vitamin appears to have only two functions in eukaryotes: as a cofactor for the enzymes methionine synthase and methylmalonylCoA mutase. These two functions are crucial for normal health in humans, and in particular, the formation of methionine is essential for providing methyl groups for over 100 methylation processes. Interference with the methionine synthase reaction not only depletes the body of methyl groups but also leads to the accumulation of homocysteine, a risk factor for many diseases. The syndrome pernicious anemia, characterized by lack of intrinsic factor, leads to a severe, sometimes fatal form of B12 deficiency. However, there is no sharp cutoff for B12 deficiency; rather, there is a continuous inverse relationship between serum B12 and a variety of undesirable outcomes, including neural tube defects, stroke, and dementia. The brain is particularly vulnerable; in children, inadequate B12 stunts brain and intellectual development. Suboptimal B12 status (serum B12 < 300 pmol/L) is very common, occurring in 30%–60% of the population, in particular in pregnant women and in less-developed countries. Thus, many tens of millions of people in the world may suffer harm from having a poor B12 status. Public health steps are urgently needed to correct this inadequacy.

Item Type: Book section
DOI/Identification number: 10.1016/bs.afnr.2017.11.005
Uncontrolled keywords: Cobalamin, Homocysteine, Methylmalonic acid, Memory, Cognition, Elderly, Children, Pregnancy, Brain
Subjects: Q Science
Divisions: Faculties > Sciences > School of Biosciences
Depositing User: Sue Davies
Date Deposited: 23 Mar 2018 13:52 UTC
Last Modified: 23 Jan 2020 04:14 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/66524 (The current URI for this page, for reference purposes)
Warren, Martin J.: https://orcid.org/0000-0002-6028-6456
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