What vitamin is primarily absorbed in the ileum?

Vitamin B12 is primarily absorbed in the ileum, which is the final section of the small intestine. The absorption of this vitamin is a complex process that requires intrinsic factor, a protein produced by the stomach that binds to vitamin B12. This vitamin is crucial for numerous bodily functions, including DNA synthesis, red blood cell formation, and maintaining healthy nerve cells.

While vitamins A, C, and D are also essential for various physiological functions, they are absorbed in different parts of the gastrointestinal tract. For instance, vitamin A, which is fat-soluble, is primarily absorbed in the small intestine along with dietary fats. Vitamin C, a water-soluble vitamin, is absorbed in the small intestine as well and does not require specific transport mechanisms like intrinsic factor. Vitamin D is primarily absorbed in the small intestine but is dependent on the presence of fat for its absorption.

Thus, the unique requirement of intrinsic factor for the absorption of vitamin B12 and its specific site of absorption in the ileum distinguish it as the correct answer to the question.