Zinc and copper are trace minerals needed for various functions. Zinc plays a role in numerous enzymatic reactions, DNA expression, and immune system function. Copper is involved in energy production, iron metabolism, connective tissue formation, and nerve function. An imbalance, particularly excessive zinc intake, can disrupt copper status.
How Zinc Affects Copper Absorption
High zinc intake can significantly interfere with the body’s ability to absorb copper from the diet. This interaction occurs in intestinal cells, where a protein called metallothionein plays a central role. Metallothionein binds to various metals, including zinc and copper.
When zinc intake increases, the body produces more metallothionein proteins within intestinal cells. Copper has a stronger binding affinity for metallothionein than zinc. As a result, newly synthesized metallothionein preferentially binds to copper, trapping it within the intestinal cells. This trapped copper cannot be absorbed into the bloodstream and is excreted as intestinal cells are shed. This explains why chronic excessive zinc can lead to copper deficiency.
Signs of Copper Deficiency
Copper deficiency can manifest through various signs and symptoms affecting several bodily systems. Common indications include hematological issues like anemia (unresponsive to iron supplementation) and neutropenia (reduced white blood cells). These blood abnormalities can impair oxygen transport and immune defense.
Neurological problems, such as myelopathy (affecting the spinal cord) and neuropathy (damaging peripheral nerves), can also arise. Individuals might experience gait disturbances, numbness, or tingling. Bone abnormalities like osteoporosis (weak, brittle bones) may also develop. A compromised immune system, leading to increased susceptibility to infections, is another consequence.
Safe Zinc Levels and At-Risk Groups
Copper deficiency is typically caused by chronic zinc intake significantly above recommended levels. For adults, the Recommended Dietary Allowance (RDA) for zinc is 11 mg per day for men and 8 mg per day for women. The Tolerable Upper Intake Level (UL) for adults, the maximum daily intake unlikely to cause adverse health effects, is 40 mg per day.
Copper deficiency is generally observed with prolonged zinc supplementation exceeding the UL, often at doses of 50 mg per day or more. Chronic intake of 150-300 mg daily, typically from high-dose supplements, has been reported to cause deficiencies. Higher risk groups include individuals using high-dose zinc supplements for immune support or cold remedies over several months. People with certain medical conditions affecting nutrient absorption or those using zinc-containing denture creams are also at increased risk.
Preventing and Addressing Copper Deficiency
Preventing zinc-induced copper deficiency involves mindful zinc intake, especially from supplements. It is advisable to avoid exceeding the Tolerable Upper Intake Level (UL) of 40 mg per day for adults without direct medical supervision. Relying on a balanced diet rich in zinc from food sources (e.g., meat, nuts, legumes) is safer than consistent high-dose supplementation, as dietary amounts are unlikely to cause an imbalance.
If copper deficiency is suspected due to excessive zinc, the typical approach involves discontinuing high-dose zinc supplements. Copper supplementation may be recommended, but only under healthcare professional guidance. A doctor can diagnose through blood tests and determine the appropriate course, monitoring levels to restore balance safely.