Which vitamin is primarily absorbed in the ileum?

Vitamin B12 is primarily absorbed in the ileum, which is the final section of the small intestine. This absorption process is facilitated by intrinsic factor, a protein secreted by the stomach that binds to vitamin B12 and protects it from digestive enzymes. As the complex travels through the intestines, it reaches the ileum where specialized receptors allow for the absorption of this vitamin into the bloodstream.

Other vitamins mentioned have different absorption sites; for instance, vitamin A is primarily absorbed in the duodenum and jejunum, vitamin C is absorbed mostly in the jejunum, and vitamin D, which is a fat-soluble vitamin, is absorbed in the ileum as well, but its absorption is closely associated with other mechanisms involving dietary fats and the overall fat absorption process. Vitamin B12, however, is unique in its requirement for intrinsic factor and absorption at the ileal sites, which is critical for maintaining adequate levels necessary for red blood cell production and neurological function.