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Vitamin B12Aka: Cyanocobalamin, Cobalamin

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  1. Physiology
    1. B12 dependent reactions in humans
      1. Methylmalonic acid converted to succinyl-CoA
      2. Homocysteine converted to methionine
    2. Normal B12 absorption pathway
      1. Acidic stomach environment breaks down food-bound B12
        1. Insufficient acid decreases B12 absorption
        2. Proton Pump Inhibitors suppress B12 absorption
      2. Intrinsic factor (IF) binds B12 in duodenum
        1. Intrinsic factor produced in stomach parietal cells
        2. Pernicious Anemia is autoimmune parietal cell death
        3. Insufficient IF results in decreased B12 absorption
      3. Vitamin B12 with intrinsic factor absorbed in ileum
      4. Absorbed Vitamin B12 binds Transcobalamin II
    3. Alternate B12 absorption
      1. Pathway independent of intrinsic factor and ileum
      2. Absorption of up to 1% of large oral B12 dose
      3. Allows for oral B12 supplementation
  2. Signs of Deficiency
    1. See Vitamin B12 Deficiency
    2. Megaloblastic Macrocytic Anemia
  3. Sources: Animal sources only
    1. Liver
    2. Muscle Meats
    3. Fish
    4. Eggs
    5. Dairy products
    6. Vitamin B12 fortified foods (Cereals)
  4. Doses
    1. See Vitamin B12 Supplementation
    2. Recommended daily allowance: 2.4 mcg/day
    3. Elderly:
      1. B12 Fortified foods (Cereals)
      2. Daily dietary supplement
  5. References
    1. Babior in Wilson (1991) Harrisons, McGraw, p. 1523-9
    2. Oh (2003) Am Fam Physician 67(5):979

Vitamin B 12 (C0042845)

Definition (MSH)A cobalt-containing coordination compound produced by intestinal micro-organisms and found also in soil and water. Higher plants do not concentrate vitamin B 12 from the soil and so are a poor source of the substance as compared with animal tissues. INTRINSIC FACTOR is important for the assimilation of vitamin B 12.
Definition (CSP)cyanocobalamin or cobalamin derivative with similar biological activity; a water soluble hematopoietic vitamin, absorbed in the intestine after combination with intrinsic factor.
Definition (PDQ)An essential nutrient and natural water-soluble vitamin of the B-complex family that must combine with an intrinsic factor for absorption by the intestine, Vitamin B12 (cyanocobalamin) is necessary for hematopoiesis, neural metabolism, DNA and RNA production, and carbohydrate, fat, and protein metabolism. B12 improves iron functions in the metabolic cycle and assists folic acid in choline synthesis. B12 metabolism is interconnected with that of folic acid. Vitamin B12 deficiency causes pernicious anemia, megaloblastic anemia, and neurologic lesions. Check for "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=530928&idtype=1" active clinical trials or "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=530928&idtype=1&closed=1" closed clinical trials using this agent. ("http://nciterms.nci.nih.gov:80/NCIBrowser/ConceptReport.jsp?dictionary=NCI_Thesaurus&code=C939" NCI Thesaurus)
Definition (NCI)An essential nutrient and natural water-soluble vitamin of the B-complex family that must combine with an intrinsic factor for absorption by the intestine, Cyanocobalamin is necessary for hematopoiesis, neural metabolism, DNA and RNA production, and carbohydrate, fat, and protein metabolism. B12 improves iron functions in the metabolic cycle and assists folic acid in choline synthesis. B12 metabolism is interconnected with that of folic acid. Vitamin B12 deficiency causes pernicious anemia, megaloblastic anemia, and neurologic lesions. (NCI04)
ConceptsOrganic Chemical (T109) , Pharmacologic Substance (T121) , Vitamin (T127)
MSHD014805
EnglishB12 - Cyanocobalamin, B12 - Cyanocobalamin prep, B12 - Vitamin B12, B12 Vitamin, Cyanocobalamin, Cyanocobalamin preparation, Cyanocobalamin product, CYANOCOBALMIN, CYANOCOBALMIN PREPARATION, VIT B12, Vitamin B 12, VITAMIN B A 12, Vitamin B<sub>12</sub>, Vitamin B<sub>12</sub> preparation, Vitamin B>12<, Vitamin B>12< preparation, Vitamin B12, vitamin B12 compound, Vitamin B12 preparation, Vitamin-B12
SpanishB12, cianocobalamina, preparado con cianocobalamina, preparado con vitamina B<sub>12</sub>, preparado con vitamina B>12<, preparado con vitamina B12
Parent ConceptsVitamin B Complex (C0042849), Vitamin B 12 (C0042845), Cobalamins (C0086024), Corrinoids (C1256766), B Vitamin Family (C1704763), Intrinsic factor (C0021918), TO BE DELETED INGREDIENT PREPARATIONS (C1377153), Unclassified Ingredient Preparations (C1377282), Vitamin B complex preparation (C0304893), Vitamin B12 - category (C1689902), Ambiguous concept (C1274012), Duplicate concept (C1274013)
SourcesAOD, CSP, LNC, MSH, MTH, MTHSPL, NCI, NDFRT, PDQ, RXNORM, SCTSPA, SNOMEDCT, VANDF
Derived from the NIH UMLS (Unified Medical Language System)



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