The competitive interaction between zinc and copper occurs when zinc is taken through which route?

• A. Intravenous zinc
• B. Through the gastrointestinal tract
• C. Subcutaneous zinc
• D. Intramuscular zinc

Answer: (B)

Zinc and copper compete for absorption mainly in the gut. When zinc is taken orally in high amounts, the enterocytes lining the small intestine upregulate metallothionein, a protein that binds copper. The bound copper is trapped in these cells and shed when the cells turn over, reducing copper entering the bloodstream and potentially leading to copper deficiency. Because this competition occurs at the site of intestinal absorption, routes that bypass the gastrointestinal tract—such as intravenous, subcutaneous, or intramuscular administration—don’t trigger the same intestinal competition. Therefore, the competitive interaction between zinc and copper occurs when zinc is taken through the gastrointestinal tract.