Does cast-iron cookware add iron to foods?
Marni writes: “I have heard that cooking in cast-iron pans can increase the iron content of some foods. Is this a safe source of iron and are there any foods that I shouldn’t cook in cast-iron?
You heard correctly, Marni. Acidic foods like tomatoes can react with the metal in a cast-iron skillet and absorb iron molecules from the pan. The greater the acidity of the food and the longer you cook it, the more iron is transferred to the food. In addition, foods that contain more water also seem to absorb more iron.
How much iron does food absorb from cast-iron cookware?
How much of a difference does this make in the iron content of your meal? Potentially, a lot. Researchers cooked several foods in new cast-iron skillets and found, for example, that the amount of iron in spaghetti sauce increased from less than 1 milligram to almost 6 mg per serving. (For reference, the recommended daily intake for adult women is 18 mg per day.) Applesauce absorbed even more, going from less than half a milligram to more than 7 mg per serving. Scrambling eggs in a new iron skillet increased the iron content from 1.5 mg to almost 5 mg. But you probably won't be adding quite as much iron to your foods as the researchers in this study because they were using new pans.
Older cast-iron pans, which have become well-seasoned through use, tend to transfer less iron to food. This isn't because the iron in the pan has been used up; it's because a well-seasoned cast-iron pan has a thin coating that is formed when fat is heated to high temperatures in the pan. This coating makes the pan less reactive with the acid in foods. Cast-iron pans that are coated with enamel, by the way, will not add iron to foods.