Mechanistically, how can high dietary iron intake reduce copper absorption in the intestine?

• A. Iron increases gut motility so dramatically that copper-containing foods pass too quickly through the intestine to be digested and absorbed, and this is the primary reason copper decreases.
• B. High iron intake stimulates bile synthesis that binds copper and sends it back to the liver for storage, thereby increasing apparent copper absorption while actually decreasing functional copper status.
• C. Iron and copper share some intestinal transport pathways and competitive uptake mechanisms; when luminal iron is high, it competes for absorption and can reduce copper uptake through shared transporters.
• D. High iron intake chemically converts copper into an insoluble polymer in the stomach which is then excreted and cannot be absorbed, a process unique to iron that does not involve transporters.

Answer: (C)