A 40-year-old woman with a history of Roux-en-Y gastric bypass surgery 3 years ago presents with fatigue, pallor, and pica. Peripheral smear shows microcytic hypochromic anemia with pencil cells. Serum ferritin is 6 ng/mL. Which dietary factor most significantly impairs non-heme iron absorption in this patient's postsurgical anatomy?

• A Accelerated intestinal transit reducing contact time with the jejunal mucosa
• B Bacterial overgrowth in the blind loop consuming dietary iron
• C Reduced gastric acid secretion and bypass of the duodenum, the primary site of non-heme iron absorption ✓
• D Loss of intrinsic factor secretion preventing iron-B12 complex formation

Explanation

Non-heme iron (Fe3+) requires gastric acid for solubilization and reduction to Fe2+ by duodenal cytochrome B (DcytB) before uptake by DMT1 on duodenal enterocytes. Gastric bypass reduces acid production and bypasses the duodenum and proximal jejunum, the primary absorptive sites. This is the dominant mechanism of post-bypass iron deficiency. Option B is a distractor; bacterial overgrowth can cause B12 deficiency, not iron deficiency. Option A is less relevant because iron absorption is primarily duodenal, not jejunal. Option D is wrong because intrinsic factor binds B12, not iron.

Reference: Bailey and Love's Short Practice of Surgery, 28th ed.

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Written and medically reviewed by the StethoPrep medical team.