Intrinsic factor is required for the absorption of which vitamin?

• A. Vitamin C
• B. Vitamin D
• C. Vitamin B12
• D. Vitamin A

Answer: (C)

Intrinsic factor is essential for absorbing vitamin B12 in the terminal ileum. It is a glycoprotein produced by gastric parietal cells that binds B12 in the stomach. The B12-intrinsic factor complex is recognized by receptors in the ileum and transported into the bloodstream, allowing B12 utilization. Without intrinsic factor, B12 absorption drops dramatically, leading to deficiency and related problems like megaloblastic anemia and neuropathy. Other vitamins don’t rely on intrinsic factor: vitamin C is absorbed by specific transport mechanisms in the small intestine, while vitamins D and A are fat-soluble and absorbed with bile acids and dietary fats.