So that’s what iron does, and why we need it. How do cast iron pans play into the story?

Cottage cooking lore has us believe that the iron in the pan transfers to the food it cooks, which we then eat. For example, a food naturally low in iron — say, a carrot — could deliver more of the mineral if it picks up the available iron from the cast iron skillet it’s roasted in. Sounds great, right? Well, only if the science is there to back up the theory.

The science behind cast iron mineral transfer

Before we go any further, here’s the brass tacks (iron tacks?): Cooking with cast iron will transfer a small amount of the mineral from the pan to your food to your body. Unfortunately, the amount of mineral transfer is so small, it’s hard to make a case for the skillets and pans as an important source of iron.

Here’s what #science has to say about it: A 2003 study tried to determine whether cast iron food prep could help mitigate anemia in developing countries, but found there to be no conclusive evidence in support of the skillets. Although the study’s authors found promising results, they ultimately concluded that further evidence was needed to make greater claims about the efficacy of cast iron in mineral transfer for anemia. In other words, hemoglobin production did increase in some individuals, but not in a systematic or data-driven, reliable pattern.

There’s another crucial element in iron transfer: The need for an acidic component to strip the pan of its iron! A Korean study completed in 2020 showed that acidic agents were the catalyst to pulling minerals from cast iron cookware. Conversely, the study also revealed that oiling cast iron reduced acid-induced mineral leaching.

So what does this mean? If you’re not cooking with acidic ingredients (and ideally, high heat), you won’t be pulling iron, or any other minerals, from the pan into your food. According to the authors, “the release of toxic metals was highly dependent on pH.” Acidic foods are slightly corrosive, and will “strip” the pan of microscopic layers of its coating. In other words, you’re more likely to absorb a skillet’s iron through a meal cooked in it than you are from licking the pan straight out of the cupboard (which would be weird).

As you may have already guessed, here’s the sticky wicket: If you want your cast iron skillet to be truly nonstick, it won’t transfer much, if any, iron to your food. The very thing that makes a cast iron pan great for searing and sautéing — that oil and fat buildup known as “seasoning” — is what hinders iron transfer. But as a reminder, even if you were cooking everything in vinegar and tomatoes, the acidic stripping would pull negligible amounts of iron from the pan (certainly not enough to see a quantifiable difference in your body’s mineral makeup).

What about other pans?

Cast iron pans aren’t unique in their ability to transfer minerals to the food they cook. A 1992 study showed that stainless steel pans can do the same. The study created an acidic environment in stainless steel cookware (you do the same thing every time you make tomato sauce) and brought it to boiling temperature. The result was that a variety of minerals did seep into the food at a small level. Unfortunately, iron wasn’t the only mineral — nickel and chromium were also absorbed; and these minerals are thought to be harmful to humans. We should note here that once again, the amount of mineral transfer wasn’t large enough to be worrisome. So don’t go hurling your favorite stainless steel saucepan out the window anytime soon.

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