Where is vitamin B12 absorbed in the digestive system?

Vitamin B12, also known as cobalamin, is primarily absorbed in the ileum, which is the final section of the small intestine. This absorption process involves specialized receptors called cubulin that are located on the surface of the enterocytes (intestinal cells) in the ileum.

During digestion, vitamin B12 is released from food proteins in the acidic environment of the stomach and then binds to a protein called intrinsic factor, which is secreted by parietal cells in the stomach. Intrinsic factor protects B12 and facilitates its transport to the ileum. Once in the ileum, the B12-intrinsic factor complex binds to cubulin receptors on the enterocytes, allowing the vitamin to be absorbed into the bloodstream.

This process is crucial for the proper absorption of vitamin B12, as deficiencies can lead to severe neurological issues and megaloblastic anemia. Understanding the specific role of the ileum and the interaction with cubulin receptors is vital for grasping how the body utilizes this essential nutrient.