Which supplement competes with copper for absorption when given enterally?

• A. Enteral iron supplementation
• B. Enteral zinc supplementation
• C. Enteral calcium supplementation
• D. Enteral vitamin B12 supplementation

Answer: (B)

Zinc supplementation can compete with copper for absorption in the gut. When zinc intake is high, enterocytes ramp up metallothionein, a metal-binding protein. Metallothionein binds copper strongly, trapping it inside the intestinal cells and preventing it from entering the bloodstream. This reduces copper absorption and can lead to copper deficiency even if copper intake is adequate.

Other supplements don’t compete with copper in the same way. Iron, calcium, and vitamin B12 are absorbed through different pathways or mechanisms and do not cause the same enterocyte-level competition as zinc.