VITAMIN B12 (CYANOCOBALAMIN)
- Water soluble vitamin
- Found in meat, fish and animal products (milk, eggs)
- Not found in vegetables.
- Stored in the body mainly in the liver (2-3 mg) which is enough for more than 2 yrs.
Absorption & Transport of B12
- B12 in the food comes in the stomach & is released from the food by gastric acid.
- Free B12 binds with a substance called “intrinsic factor” in the stomach (which is secreted by parietal cells)
- This intrinsic factor & B12 complex reaches the terminal ileum
- B12 is then released from I.F. & absorbed in the terminal ileum & is carried to all the tissues
- Some B12 is absorbed in the duodenum without intrinsic factor (direct absorption)
IMPORTANT CAUSES OF B12 DEFICIENCY
- Decreased intake (eg. in vegetarians)
- Decreased gastric acid (PPIs, old age);
- Loss of intrinsic factor; Gastrectomy & Pernicious anemia
- Chronic pancreatitis
- Terminal ileal disease (Crohn’s Disease, surgery, celiac)
- Metformin (decreases absorption)
- Infection by Diphyllobothrium latum (fish latum)