Copper

Copper is an essential cofactor for enzymes involved in iron metabolism, connective tissue and antioxidant defence. Outright deficiency is uncommon but can arise from malabsorption or, notably, from taking high-dose zinc for a long time, which blocks copper absorption.

For most people diet supplies enough, and the main practical point is balance: if you supplement zinc heavily, you may need some copper to avoid a deficiency. Standalone high-dose copper is rarely necessary and is toxic in excess.

Sources

• PubMed: copper supplementation deficiency zinc balance (research overview)