Which statement correctly links gastrectomy to vitamin B12 deficiency?

• A. Decreased intrinsic factor production results in decreased vitamin B12
• B. Increased intrinsic factor production results in increased vitamin B12
• C. Vitamin B12 absorption is unaffected by intrinsic factor
• D. Intrinsic factor increases iron absorption

Answer: (A)

Intrinsic factor, produced by stomach parietal cells, is essential for vitamin B12 absorption in the distal ileum. When gastrectomy reduces or removes these cells, intrinsic factor levels fall, so vitamin B12 cannot be efficiently absorbed, leading to deficiency. This is why the statement that decreased intrinsic factor production results in decreased vitamin B12 is correct. If intrinsic factor were increased, B12 absorption would rise; however, gastrectomy typically lowers intrinsic factor, not raises it. Vitamin B12 absorption is not independent of intrinsic factor, and the intrinsic factor, by itself, does not affect iron absorption.