How is vitamin B12 absorbed?

Answer 1

The process of B12 may be complex but it follows a straightforward progression:

1: B12 and R protein (produced in Salivary Glands) travel from the mouth to the stomach unbound

2: In the Stomach, R Protein binds to B12 to protect it from degradation. Stomach releases intrinsic factor from parietal cells to travel with bound R/B12 into the small intestine

3: Enzymes from the pancreas cleave R protein from B12, B12 then binds to intrinsic factor

4: Bound Intrinsic/B12 travels to ileum where it is absorbed and transported all over the body

If I remember correctly it should take 3-5 hours depending on efficiency of parietal cells in the stomach, and exposure time on the brush border.

Answer 2

B12 is absorbed in the intestines by way of something called the intrinsic factor(released bu the stomach). That is why when someone has a surgery such as gastric bypass or gastric sleeve- disease such as celiac disease or malabsorption syndrome they are at risk for pernicious anemia(anemia caused by b12 deficiency). Though b12 is absorbed in the stomach it is also stored on the liver. It is the only b vitamin stored in the body.