Vitamin B12: Physiology, Dietary Sources, and Requirements

Research output: Chapter in Book/Report/Conference proceedingChapter

5 Scopus citations


Vitamin B12, a cobalamin, is required for only two enzyme reactions in humans and animals: The conversion of methylmalonyl CoA to succinyl CoA and addition of a methyl group to homocysteine to form methionine. Vitamin B12 does not occur in plants, and the only natural sources are animal source foods, a low intake of which can cause deficiency. Vitamin B12 release from food and its subsequent absorption are complex processes, which can be impaired by many factors leading to depletion of body stores over time. Several laboratory tests can be used to assess vitamin B12 status but the mechanisms underlying the neurological and cognitive symptoms of deficiency are not yet understood.

Original languageEnglish (US)
Title of host publicationEncyclopedia of Human Nutrition
PublisherElsevier Inc.
Number of pages6
ISBN (Electronic)9780123848857
ISBN (Print)9780123750839
StatePublished - Jan 1 2012


  • Anemia
  • Cobalamin
  • DNA
  • Folate
  • Haptocorrin
  • Homocysteine
  • Intrinsic factor
  • Macrocytosis
  • Megaloblastic anemia
  • Methionine
  • Methylmalonic acid
  • Myelin
  • S-adenosyl methionine
  • Transcobalamin
  • Vitamin B

ASJC Scopus subject areas

  • Medicine(all)


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