Vitamin B12 is the last vitamin discovered and is essential for nervous system and blood cell formation. Deficiency is common, affecting over 50% of women and 30% of men. It is produced by bacteria and contains cobalt. Absorption requires intrinsic factor in the stomach and occurs in the ileum. Deficiency can result from lack of intake, intrinsic factor deficiency causing pernicious anemia, or absorption issues from diseases or drugs impairing absorption. Diagnosis involves blood tests and the Schilling test to identify the cause of deficiency. Treatment involves B12 injections or high dose oral supplementation.

1. Vitamin B12
Dr. C. Taklikar
Assistant Professor
Dept. of B&N
AIIH & PH

2. Contents
• Introduction
• Prevalence
• Chemistry
• Absorption
• Storage Excretion
• Functions of VitB12
• Source
• RDA
• Deficiency
• Diagnosis and treatment

3. Introduction
• Last member of B vitamins discovered in 1948
• Simultaneously in UK and US
• US- Mary shrob
• Lactobacillus lactis Dorner
• UK-Lester Smith-purer extracts of liver for ant
pernicious activity

4. • Produced by Fungi and Bacteria
• Even millionth of a gram is active
• Only Vitamin containing cobalt

5. Prevalence
• Subclinical deficiency >50% women
• Males >30%
• School age children-45%

6. Chemistry
• Contains cyanide group and cobalt.
• Empirical formula is C63H90O14N14PCo
• Red crystalline.
• Slightly soluble in water.

7. Chemistry
• Cobalamin
• Vitamin B12a –aquacobalamin
• Vitamin B12b-hydroxycobalamin

8. Chemistry
• Adenosylcobalamin- RBC and tissues.
• Methylcobalamin-70% in liver.
• Streptomyces griseus
• Streptomyces aurofaciens

9. Absorption
• Intrinsic factor
• Glycoprotein
• 1 mg binds to 1 mcg of B12
• Parietal cells
• R protein
• Active absorption: takes place in ileum
• Passive absorption: throughout length of small intestine

10. Serum Vitamin B12
• Transcobalamin I & II
• Normal level: 200-1000Pcg/ml
• High level seen in Liver necrosis and cirrhosis

11. Storage
• Stored in the form of coenzyme.
• Total body store-2mg
• Liver stores 1 mg
• Forms- methylcobalamin, adenosylcobalamin
and hydroxycobalamin

12. Excretion
• Urine: 30 pgm/day
• Faces: 10 micrograms.
• Milk: Conc. Same as blood

13. Functions
• Adenosylcobalamin required for conversion of
homocysteine to methionine.
• Synthesis of DNA
• Act as coenzyme for methionine synthase &
methylmalonyl mutase.
• Normal functioning of Nervous system ,bone
marrow cells, and GIT

14. Sources
• Synthesized by bacteria in soil, water in human
and animal intestine.

15. Source Vit B12 mcg/100gm
Beef
Muscle
Kidney
heart
liver
2-8
20-50
25
50-130
Cheese 1.4-3.6
Chicken liver 8
Egg yolk 1.2
Fish 10-25
Lamb leg 8
Meat 3.5
Cow milk 0.2-0.6
Pork 0.1-5

16. RDA
Group VitaminB12 mcg/day
Men 1.0
Women (NPNL) 1.0
Pregnant women 1.2
Lactating Women 1.5
Infancy 0.2
Children 1-9 yrs 0.2-1.0
Adolescent 10-12 yrs 0.2-1.0
Adolescent 13-17 yrs 0.2-1.0

17. Deficiency
• 1.Lack of intake
• 2.Lack of intrinsic factor
-pernicious anemia
-Stomach resection
- Congenital abnormality

18. Contd.
• 3.Deficiency of Intestinal absorption
-T.B, sprue, resection
-Diphyllobothrium latum
-Stagnant loop syndrome
-Giardia Lamblia
-Congenital deficiency of receptors
-Transcobalamin II deficiency
-Drugs: Neomycin, colchicine,
PAS, OCP, alcohol

19. • 4. Excessive demand in pregnancy

20. Intake deficiency IF deficiency Absorption defect Excess
demand
Lack of
Animal
protein
Congenital
Pernicious anemia
Gastrectomy
Celiac
Syndrome
Sprue
Diphyllobothrium-latum
Stagnant loop
Ileal defects
Inflammation
Resection
Drugs
Malabsorption
Pregnancy

21. Diagnosis
• Hematological:
• 1. Macroytic anemia
• 2.Megaloblast in bone marrow
• 3. Average survival time of RBC reduces

22. Diagnosis
• Neurological
1.Weakness, spasticity and extensor plantar
response, loss of joint and vibration movement
2.Bilateral symmetrical tingling, numbness,
parasthesia diminished sensations in distal parts
of limbs

23. Diagnosis
• 3.Depression, paranoia and psychosis

24. • Laboratory
Schilling test:
1 mcg radioactive B12orally
1mg of normal B12 S.C inj.
Radioactive B12-10-20% excreted in urine in 24
hrs

25. Contd.
• The test is repeated after orally administering
25-100ml gastric juice from normal person with
oral B12.
• If urinary excretion increases –IF deficiency
• If No-defect in ileum absorption
• Oral tetracycline.

26. Treatment
• Pernicious anemia:
-Injection 100mcg IM 3 times/wk foe 3 wks
-Maintenance 100mcg monthly
• Sub acute combined degeneration:
- 100 mcg alternate day till
improvement