Cooking acidic foods like tomatoes in copper cookware poses health and toxicity risks due to the accelerated leaching of copper into the food under low-pH conditions.
The claim is specific and testable. Paper [7] directly demonstrates that acidic environments (such as citric or malic acid, which mimic the acidity of foods like tomatoes) drastically increase the rate at which copper ions leach from unlined or commercial copperware. Paper [5] notes that copper cookware contains heavy metal contaminants and that acidic foods promote metal leaching into food. Therefore, the claim is supported by direct experimental evidence on pH-dependent copper release.