Copper

What Is Copper?

Copper is an essential trace mineral that functions primarily as a cofactor for enzymes that catalyze oxidation-reduction reactions. An adult body contains approximately 75-100 mg of copper, distributed in the liver (~10%), brain, kidney, heart, muscle, and bone. The liver is the primary organ for copper storage and regulation; it secretes copper into bile for elimination and into blood bound to the protein ceruloplasmin.

Key Functions

• Antioxidant defense: Copper-zinc superoxide dismutase (Cu/Zn-SOD) is one of the body's primary antioxidant enzymes, neutralizing superoxide radicals.
• Iron metabolism: Ceruloplasmin (the main copper transport protein) has ferroxidase activity — it oxidizes ferrous iron to ferric iron, enabling iron to be loaded onto transferrin for transport. Copper deficiency can therefore cause anemia even when iron stores are adequate.
• Connective tissue synthesis: Lysyl oxidase, a copper enzyme, cross-links collagen and elastin fibers, giving them tensile strength. Deficiency causes weakened connective tissue, vascular fragility, and skeletal abnormalities.
• Neurotransmitter synthesis: Dopamine beta-hydroxylase requires copper to convert dopamine to norepinephrine.
• Melanin production: Tyrosinase, a copper enzyme, catalyzes the first step in melanin biosynthesis, determining skin, hair, and eye pigmentation.
• Energy production: Cytochrome c oxidase (Complex IV), the final enzyme in the mitochondrial electron transport chain, contains two copper atoms essential for its function.

Dietary Reference Values and Food Sources

The RDA for copper is 900 mcg (0.9 mg) per day for adults. The UL is 10,000 mcg/day. Rich food sources include:

• Beef liver (3 oz): ~12,400 mcg
• Oysters (3 oz): ~4,850 mcg
• Shiitake mushrooms, cooked (1 cup): ~1,300 mcg
• Cashews (1 oz): ~630 mcg
• Dark chocolate (1 oz): ~500 mcg
• Sunflower seeds (1 oz): ~519 mcg

Deficiency and Toxicity

Copper deficiency is uncommon but can result from malabsorption, excessive zinc supplementation (zinc competes with copper for absorption via metallothionein), gastric bypass surgery, or exclusively formula-fed premature infants. Symptoms include anemia, neutropenia, bone abnormalities, neurological dysfunction, and depigmentation. Wilson's disease is a genetic disorder causing toxic copper accumulation in the liver and brain. Menkes disease is a fatal X-linked disorder of copper transport causing severe copper deficiency in affected infants.