Iron is a mineral that is found in every living cell. Iron exists in two forms—heme and nonheme. Heme iron is part of the hemoglobin and myoglobin molecules in animal tissues. About 40% of the iron in meat is in the heme form. Nonheme iron comes from animal tissues other than hemoglobin and myoglobin and from plant tissues. It is found in meats, eggs, milk, vegetables, grains, and other plant foods. The body absorbs heme iron much more efficiently than nonheme iron. Much of the iron in our diet comes from foods, such as breads and cereals that are fortified with this mineral. Worldwide, iron deficiency anemia is the most common form of malnutrition.
Iron's functions include:
Iron needs are greatest during times of rapid growth—childhood, adolescence, and pregnancy. Also, women have higher requirements than men, to replace the iron that is lost with monthly menstruation.
Groups of people who are susceptible to being iron deficient are:
There are no symptoms of iron deficiency unless you become anemic. If not corrected, iron deficiency can progress to anemia. Symptoms of anemia include:
Iron-deficiency anemia is usually treated by increasing iron intake through dietary sources and iron supplementation.
At high levels, iron is toxic. And since the body has no effective means of excreting excess iron, it is possible, although not very common, for iron to accumulate. Iron pills and supplements containing iron that are designed for adults can cause poisoning in children.
Symptoms of iron toxicity include:
Major Food Sources
Food Sources of Mostly Heme Iron
Food Sources of Nonheme Iron
Other Health Implications Related to Iron
People with the genetic disease hemochromatosis absorb excessive amounts of iron. This leads to a buildup of iron in the bloodstream and in certain organs, including the liver, muscles, pancreas, and heart. Signs and symptoms of disease usually do not appear until midlife. People of Northern European descent and men are at higher risk. Without treatment, high levels of iron can damage these organs. Treatment involves eating a diet low in iron and donating blood regularly.
Heart Disease and Cancer
Some research has suggested that excess levels of iron in the body may lead to an increased risk for heart disease or cancer. These effects may be due to how the body metabolizes iron, as opposed to how much iron is in the diet. However, the research in these areas is still inconclusive.
Tips for Increasing Your Iron Intake
The amount of iron your body absorbs varies depending on several factors. For example, your body will absorb more iron from foods when your iron stores are low and will absorb less when stores are sufficient.
In addition, certain dietary factors affect absorption:
To increase your intake and absorption of dietary iron, try the following:
Academy of Nutrition and Dietetics
Vegetarian Resource Group
Dietitians of Canada
Centers for Disease Control and Prevention. Recommendations to prevent and control iron deficiency in the United States. Morbidity and Mortality Weekly Report. 1998;47:1-32. Available at: http://wonder.cdc.gov/wonder/PrevGuid/m0051880/m0051880.asp .
Duyff R. The American Dietetic Association's Complete Nutrition Guide . Chronimed Publishing; 1998.
Dietary supplement fact sheet: iron. Office of Dietary Supplements website. Available at: http://ods.od.nih.gov/factsheets/iron.asp. Accessed August 1, 2012.
Pennington J. Bowes & Church's Food Values of Portions Commonly Used . 17th ed. Lippincott Williams & Wilkins; 1998.
Wardlaw G, Insel P. Perspectives in Nutrition . 2nd ed. Mosby Year Book, Inc.; 1993.
Last reviewed August 2012 by Brian Randall, MD