What vitamin absorption is most likely to be impaired with chronic use of proton pump inhibitor therapy?

• A. Vitamin B12
• B. Vitamin A
• C. Vitamin C
• D. Vitamin B6

Answer: (A)

Chronic proton pump inhibitor use lowers gastric acidity, and that acidic environment is essential to release vitamin B12 from dietary protein so it can bind to intrinsic factor for absorption later in the small intestine. When acid is suppressed, less B12 is freed, fewer B12–intrinsic factor complexes form, and overall absorption of B12 decreases. B12 stores can last for years, so deficiency may develop gradually with long-term therapy. The other vitamins listed don’t rely on stomach acid to the same extent for their absorption—B6 is absorbed mainly in the small intestine, vitamin C uses intestinal transporters, and vitamin A absorption depends more on fat digestion and bile. Thus vitamin B12 is the vitamin most likely to be impaired with chronic PPI use.