Copper has been used for cooking vessels and drinking mugs for centuries, valued for its superior heat conductivity and attractive appearance. Whether it is safe to eat off copper depends entirely on the item’s construction and use. Safety requires a non-reactive barrier to prevent the metal from interacting directly with food. When properly lined, copper is safe; otherwise, it poses a risk.
Understanding Copper Toxicity
Copper is an essential trace mineral required for various functions, including energy production and iron metabolism. The body tightly controls copper levels, primarily excreting excess amounts through bile. Toxicity occurs when copper intake overwhelms these homeostatic controls, leading to a buildup in the body.
Uncoated copper surfaces leach copper ions into food, especially when exposed to heat or moisture. This excessive intake causes acute copper poisoning, known as copper toxicosis. Immediate reactions often include gastrointestinal distress, such as nausea, vomiting, and diarrhea. Chronic exposure to excessive amounts can damage organs like the liver and kidneys over time.
Identifying Safe and Unsafe Copper Cookware
The distinction between safe and unsafe copper items rests on the presence and integrity of a protective lining. Modern, food-grade copper cookware uses a non-reactive metal to cover the interior cooking surface. The most common lining materials are durable stainless steel or traditional tin, which acts as a barrier between the copper and the food.
Stainless steel linings are favored for durability, resistance to scratching, and ability to withstand high heat. Tin is also a non-reactive metal, historically used for centuries, but it is softer and has a lower melting point of approximately 450°F (232°C). Unlined copper items are considered unsafe for general food preparation.
Unsafe items include decorative copper pots, vintage cookware with worn linings, and unlined drinking vessels like Moscow Mule mugs. When the lining is scratched, worn, or absent, the reactive copper surface is exposed. Using these vessels for direct food contact or prolonged holding of beverages presents a risk of copper leaching.
Guidelines for Safe Food Preparation and Storage
The primary rule for safe copper use is to strictly limit contact between food and unlined copper surfaces, especially with acidic ingredients. Highly acidic foods, such as tomatoes, vinegars, citrus juices, and wine, dramatically accelerate copper leaching. The Food and Drug Administration (FDA) suggests avoiding copper use for foods with a pH below 6.0 unless a protective lining is present.
Even with lined cookware, care must be taken to maintain the integrity of the inner barrier. Abrasive cleaning tools or metal utensils can scratch the lining, particularly softer tin, exposing the reactive copper beneath. For tin-lined pots, using only soft utensils like wood or silicone is advisable to prevent premature wear.
Copper should never be used for long-term food storage, even if lined. Prolonged contact time increases the opportunity for copper ions to dissolve into the contents. Meals should be transferred to non-reactive containers immediately after cooking. Beverages should also not be left sitting in unlined copper mugs for extended periods, as continuous contact increases the potential for ingesting excessive copper.