Cooking canned food directly in the can is not recommended, even though it’s a common practice in camping and emergency situations. The main concerns are chemical leaching from the can’s interior lining, increased metal migration into your food, and the physical danger of heating a sealed container. While eating food heated briefly in a can once or twice is unlikely to cause immediate harm, making it a habit introduces unnecessary chemical exposure that’s easy to avoid.
What’s Inside the Can Besides Food
Most metal food cans aren’t bare metal on the inside. They’re coated with a thin layer of epoxy resin or another polymer lining designed to prevent the food from reacting with the metal. Many of these linings contain bisphenol A (BPA), a synthetic compound that acts as an endocrine disruptor at certain exposure levels. BPA-based epoxy resins have been one of the most common can lining materials for decades, and the FDA still permits their use in food cans for adults, though it banned BPA-based linings in infant formula packaging.
Some manufacturers have switched to “BPA-free” alternatives, but the replacement compounds aren’t necessarily safer when heated. These linings were designed to protect food during shelf storage at room temperature or mild pasteurization during the canning process. They were not engineered for stovetop, oven, or campfire temperatures. Polymer linings can begin to soften and degrade at temperatures well below the boiling point of many cooking applications, with some common plastics showing degradation starting around 120°C (248°F). When you heat a can on a burner or over coals, you can easily exceed these thresholds, accelerating the release of chemicals from the lining into your food.
Metal Migration Gets Worse With Heat and Acidity
Even if the lining holds up, the metal itself becomes a concern. Research on aluminum cookware shows that metal migration into food increases dramatically with both temperature and acidity. When researchers heated acidic solutions (just 0.5% citric acid, roughly equivalent to a mild tomato sauce) in aluminum at 160°C for two hours, aluminum concentrations reached 638 mg/L, exceeding the European safety transfer limit by more than 100 times. With plain water under the same conditions, concentrations stayed far lower at around 0.7 mg/L.
Most food cans are made of steel, sometimes with a tin coating, rather than aluminum. But the principle holds: acidic foods like tomatoes, beans in tomato sauce, fruits, and anything with vinegar or citrus will pull more metal into solution when heated. In one striking example, fish patties prepared with a lemon juice marinade in aluminum pans picked up 74.6 mg/L of aluminum, exceeding the safety limit by a factor of 15. The combination of heat plus acid is what makes metal migration particularly aggressive, and canned foods tend to be on the acidic side.
The Sealed Can Problem
If you’re thinking of heating a can without opening it first, that’s a genuinely dangerous idea. As the contents heat up, pressure builds inside the sealed container with no way to escape. The can can rupture or explode, sending hot food and sharp metal in all directions. This isn’t a theoretical risk. Always open a can before heating its contents, regardless of the method you choose.
Lead Solder Is No Longer a Concern
One piece of good news: if you’re using cans manufactured in the United States, lead isn’t an issue. The U.S. canned food industry stopped using lead-soldered seams in 1991, and the FDA formally banned lead solder in all food cans, including imports, in 1995. Modern cans are welded shut at the seams and may have an enamel or vinyl protective coating on the interior. If you’re dealing with very old cans or cans from countries with less stringent manufacturing standards, lead could still be a factor, but for typical grocery store products it’s not.
What to Do Instead
The simplest fix is to transfer the food to a pot, pan, or microwave-safe dish before heating it. This eliminates the lining degradation issue, reduces metal migration, and gives you better temperature control. The whole process takes about five extra seconds.
If you’re camping or in a survival situation where you have no other cookware, heating food in an opened can over low heat for a short time is a reasonable compromise. Keep the temperature as low as possible, stir frequently, and remove the can from the heat source as soon as the food is warm. Avoid doing this with highly acidic foods like tomato-based soups or fruit, since acidity accelerates chemical and metal leaching. And treat it as an occasional workaround, not a regular cooking method.
For anyone heating canned food at home on a regular basis, there’s simply no reason to leave it in the can. The linings weren’t tested for direct cooking temperatures, the metal migration data is clear about the risks of combining heat with acidic foods, and transferring to proper cookware costs you nothing.