The Ache: Lack of dietary iron reduces production of the blood protein hemoglobin, resulting in iron-deficiency anemia, a condition marked by extreme fatigue. While iron deficiency is more common in developing countries than in the U.S., women, children, vegetarians and blood donors are at greater risk.

The Claim: Cast-iron pots and pans release iron into your food. Cooking in them is an inexpensive and convenient way to add the mineral to your diet, some scientists say.

The Verdict: It is true that cooking with cast iron can potentially add iron to your food, but the amount transferred and how well the body can absorb it varies widely depending on the acidity of the food and the cooking time, according to scientific studies. Separately, an iron ingot in the shape of a fish, when simmered in soup, was found in a recent study to cut anemia levels in rural Cambodian women, although the researchers say those results don’t apply to cast-iron skillets.

People with an iron deficiency shouldn’t rely on cooking in cast iron, says Sara Haas, a dietitian and spokeswoman for the Academy of Nutrition and Dietetics, an organization of food and nutrition professionals. But it could be “a good way” to add iron—in addition to eating iron-rich foods— for anyone who is at risk for not getting enough, she says.

Since iron is soluble in acid, it will transfer to food more readily when cooking acidic foods, such as tomatoes or apples, says Fergus Clydesdale, a professor in the Department of Food Science at University of Massachusetts Amherst. Cooking in water will result in more iron transfer than frying in oil, he adds.

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For this reason, the fish, from Canada’s Lucky Iron Fish Inc., which has sold its fish-shaped ingot on the Web since 2014, is recommended for use in soups or boiled with drinking water. The company also advises adding acids, such as citrus juice or vinegar. In a study of 304 women in three Cambodian villages, published in 2015 in the journal Tropical Medicine & Surgery, use of the fish for a year increased hemoglobin concentration in the blood, compared with a control group that didn’t use the fish, and cut the prevalence of anemia by 46%. The fish costs $25, and for every fish purchased on its site, the company donates one to a needy community.

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