How are vitamins B12 and folate absorbed differently?

• A. Both absorbed exclusively in stomach
• B. Folate is absorbed in the duodenum mostly via active transport
• C. B12 absorption occurs in the ileum with intrinsic factor; folate absorbed mainly in proximal small intestine via active transport
• D. Folate requires intrinsic factor; B12 does not

Answer: (C)

Vitamins B12 and folate are absorbed in different parts of the gut and by different mechanisms, which is why their handling in the intestine is distinct. B12 absorption hinges on intrinsic factor, a protein produced by stomach cells. The B12-intrinsic factor complex travels to the ileum, where it binds to specific receptors and is taken into the enterocytes. This makes its absorption strongly dependent on intrinsic factor and localized to the distal small intestine.

Folate is absorbed predominantly earlier in the small intestine, in the proximal portion (duodenum and jejunum), mainly through active transport using folate-specific transporters such as the proton-coupled folate transporter. It does not require intrinsic factor, though at very high concentrations some folate can be absorbed by passive diffusion.

So the correct idea is that B12 is absorbed in the ileum with intrinsic factor, while folate is absorbed mainly in the proximal small intestine via active transport. The other statements misstate either the sites or the need for intrinsic factor.