To Your Health

Does dairy consumption at a meal interfere with iron absorption?

Q. I've read that using dairy products at a meal can interfere with iron absorption. Is this true?

A. It is true that milk and some other dairy products tend to interfere with iron absorption, but this is more like the beginning of the story rather than the end. Iron is one of the nutrients that we must maintain tight control over, and the manner in which the body extracts the correct amount of iron we need from the food we eat is a rich tapestry of interactions.

Your body's ability to absorb iron is increased when iron is deficient, which is fortunate because, worldwide, iron-deficiency anemia is a serious problem. To an even greater extent, iron-absorption capacity is decreased when there is a danger of iron overload, which is even more fortunate for us. Here in America the risk of iron overload, especially among men and postmenopausal women, is a growing concern. Certain inherited conditions can result in dangerous accumulations of iron. Also, the standard medical treatment for some medical conditions results in iron overload due to frequent blood transfusions. In these conditions it is essential for the body to reduce absorption of iron from dietary sources.

There are certain foods and food supplements that enhance iron absorption and others that inhibit it. Children and women in their childbearing years need enhanced iron absorption, so combining iron-rich foods with high-acid foods in a meal in order to improve absorption makes sense. The fermentation of milk produces lactic acid and other organic acids that increase the absorption of iron, so for these people there are benefits to a meal that combines yogurt or buttermilk with foods rich in iron or an iron supplement. Vitamin C will enhance the absorption of iron when both vitamin C and iron are present together in the intestine, so drinking orange juice with your iron-fortified cereal is a good idea when you need to increase your iron absorption.

If you are among those who risk iron overload, you should avoid combining high-acid foods and iron-rich foods. Instead, choose foods that are generally lower in iron and combine these with foods that inhibit iron absorption such as milk and cheese. In addition, substances found in beans and cereal foods and the tannins in tea can interfere with iron absorption. Some spices, oregano for instance, decrease iron absorption.

There are two kinds of dietary iron: the iron which is present in red meat, known as heme iron, and the greater amount of iron found in vegetables, fruits, and cereals. Only about one-fifth of the iron in the American diet comes from meat. About 15% of heme iron in a meal is absorbed, and although much less nonheme iron is absorbed, there is more of this iron in our food, and the amount absorbed may vary more than 20-fold depending on the composition of a meal. You can greatly influence your total iron intake through your food choices.

Iron deficiency can rob you of stamina, but excessive iron absorption can decrease your ability to fight infections and increase your risk of cardiovascular disease and even cancer. If in doubt, blood tests to verify iron stores (ferritin) will help you adapt the absorption of iron from your food to fit your individual needs.

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