Which of the following is the main site of absorption of vitamin B12?
Most vitamins are absorbed in the upper small intestine, but vitamin B12 is absorbed in the ileum. This vitamin binds to intrinsic factor, a protein secreted by the parietal cells of the stomach, and the complex is absorbed across the ileal mucosa. Vitamin B12 absorption and folate absorption are Na+-independent. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 26. Digestion, Absorption, & Nutritional Principles. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.
Duodenum
Jejunum
Ileum
Colon