Which factor most affects vitamin B12 absorption in older adults?

Which factor most affects vitamin B12 absorption in older adults?

• A. Decreased intrinsic factor production due to atrophic gastritis.
• B. Reduced stomach acid alone.
• C. Decreased calcium absorption.
• D. Low dietary B12 intake.

Answer: (A)

The essential process is that vitamin B12 absorption depends on intrinsic factor produced by stomach parietal cells. In older adults, atrophic gastritis reduces the production of intrinsic factor, so the B12-IF complex cannot form efficiently and absorption in the ileum drops dramatically. This direct loss of intrinsic factor is the biggest barrier to B12 uptake, more impactful than changes in stomach acid alone, calcium absorption, or dietary intake. While lower stomach acid can hinder freeing B12 from food and high-dose B12 can be absorbed passively without IF, those factors don’t address the main bottleneck caused by IF deficiency.

The essential process is that vitamin B12 absorption depends on intrinsic factor produced by stomach parietal cells. In older adults, atrophic gastritis reduces the production of intrinsic factor, so the B12-IF complex cannot form efficiently and absorption in the ileum drops dramatically. This direct loss of intrinsic factor is the biggest barrier to B12 uptake, more impactful than changes in stomach acid alone, calcium absorption, or dietary intake. While lower stomach acid can hinder freeing B12 from food and high-dose B12 can be absorbed passively without IF, those factors don’t address the main bottleneck caused by IF deficiency.