Vitamin C enhances the absorption of non-heme iron from the gastrointestinal tract. Which biochemical property of vitamin C is primarily responsible for this effect?

• A It converts transferrin-bound iron to free iron
• B It chelates iron in the intestinal lumen for absorption
• C It upregulates ferroportin expression on enterocytes
• D It reduces ferric iron (Fe3+) to ferrous iron (Fe2+) ✓

Explanation

Vitamin C acts as a reducing agent, converting ferric iron (Fe3+) to the more soluble ferrous form (Fe2+), which is the form absorbed by the divalent metal transporter 1 (DMT1) on duodenal enterocytes. This is the primary mechanism by which vitamin C enhances non-heme iron absorption. The other options describe mechanisms not involving vitamin C, making them plausible but incorrect distractors.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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