There are two forms of dietary iron: heme and nonheme. Heme iron is derived from hemoglobin, the protein in red blood cells that delivers oxygen to cells. Heme iron is found in animal foods that originally contained hemoglobin, such as red meats, fish, and poultry. Iron in plant foods such as lentils and beans is arranged in a chemical structure called nonheme iron.1 This is the form of iron added to iron-enriched and iron-fortified foods. Heme iron is absorbed better than nonheme iron, but most dietary iron is nonheme iron.2 A variety of heme and nonheme sources of iron are listed in Tables 1 and 2.

Table 1: Selected Food Sources of Heme Iron3

Food Milligramsper serving % DV*
Chicken liver, cooked, 3½ ounces 12.8 70
Oysters, breaded and fried, 6 pieces 4.5 25
Beef, chuck, lean only, braised, 3 ounces 3.2 20
Clams, breaded, fried, ¾ cup 3.0 15
Beef, tenderloin, roasted, 3 ounces 3.0 15
Turkey, dark meat, roasted, 3½ ounces 2.3 10
Beef, eye of round, roasted, 3 ounces 2.2 10
Turkey, light meat, roasted, 3½ ounces 1.6 8
Chicken, leg, meat only, roasted, 3½ ounces 1.3 6
Tuna, fresh bluefin, cooked, dry heat, 3 ounces 1.1 6
Chicken, breast, roasted, 3 ounces 1.1 6
Halibut, cooked, dry heat, 3 ounces 0.9 6
Crab, blue crab, cooked, moist heat, 3 ounces 0.8 4
Pork, loin, broiled, 3 ounces 0.8 4
Tuna, white, canned in water, 3 ounces 0.8 4
Shrimp, mixed species, cooked, moist heat, 4 large 0.7 4

Table 2: Selected Food Sources of Nonheme Iron [10]

Food Milligramsper serving % DV*
Ready-to-eat cereal, 100% iron fortified, ¾ cup 18.0 100
Oatmeal, instant, fortified, prepared with water, 1 cup 10.0 60
Soybeans, mature, boiled, 1 cup 8.8 50
Lentils, boiled, 1 cup 6.6 35
Beans, kidney, mature, boiled, 1 cup 5.2 25
Beans, lima, large, mature, boiled, 1 cup 4.5 25
Beans, navy, mature, boiled, 1 cup 4.5 25
Ready-to-eat cereal, 25% iron fortified, ¾ cup 4.5 25
Beans, black, mature, boiled, 1 cup 3.6 20
Beans, pinto, mature, boiled, 1 cup 3.6 20
Molasses, blackstrap, 1 tablespoon 3.5 20
Tofu, raw, firm, ½ cup 3.4 20
Spinach, boiled, drained, ½ cup 3.2 20
Spinach, canned, drained solids ½ cup 2.5 10
Black-eyed peas (cowpeas), boiled, 1 cup 1.8 10
Spinach, frozen, chopped, boiled ½ cup 1.9 10
Grits, white, enriched, quick, prepared with water, 1 cup 1.5 8
Raisins, seedless, packed, ½ cup 1.5 8
Whole wheat bread, 1 slice 0.9 6
White bread, enriched, 1 slice 0.9 6

*DV = Daily Value. DVs are reference numbers developed by the Food and Drug Administration (FDA) to help consumers determine if a food contains a lot or a little of a specific nutrient. The FDA requires all food labels to include the percent DV (%DV) for iron. The percent DV tells you what percent of the DV is provided in one serving. The DV for iron is 18 milligrams (mg). A food providing 5% of the DV or less is a low source while a food that provides 10-19% of the DV is a good source. A food that provides 20% or more of the DV is high in that nutrient. It is important to remember that foods that provide lower percentages of the DV also contribute to a healthful diet. For foods not listed in this table, please refer to the U.S. Department of Agriculture's Nutrient Database Web site: http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl.

Iron absorption refers to the amount of dietary iron that the body obtains and uses from food. Healthy adults absorb about 10% to 15% of dietary iron, but individual absorption is influenced by several factors.4 5 6 7 8 9 10 11

Storage levels of iron have the greatest influence on iron absorption. Iron absorption increases when body stores are low. When iron stores are high, absorption decreases to help protect against toxic effects of iron overload.12 13 Iron absorption is also influenced by the type of dietary iron consumed.

Absorption of heme iron from meat proteins is efficient. Absorption of heme iron ranges from 15% to 35%, and is not significantly affected by diet.14 In contrast, 2% to 20% of nonheme iron in plant foods such as rice, maize, black beans, soybeans and wheat is absorbed.15 Nonheme iron absorption is significantly influenced by various food components.16 17 18 19 20 21 22

Meat proteins and vitamin C will improve the absorption of nonheme iron.23 24 25

Tannins (found in tea), calcium, polyphenols, and phytates (found in legumes and whole grains) can decrease absorption of nonheme iron.26 27 28 29 30 31 32 Some proteins found in soybeans also inhibit nonheme iron absorption.33 34 It is most important to include foods that enhance nonheme iron absorption when daily iron intake is less than recommended, when iron losses are high (which may occur with heavy menstrual losses), when iron requirements are high (as in pregnancy), and when only vegetarian nonheme sources of iron are consumed.

Iron is found in both animal and plant foods, but in different forms. Beef and turkey are good sources of heme iron while beans and lentils are high in nonheme iron. In addition, many foods, such as ready-to-eat cereals, are fortified with iron.

According to the 2005 Dietary Guidelines for Americans, "Nutrient needs should be met primarily through consuming foods. Foods provide an array of nutrients and other compounds that may have beneficial effects on health. In certain cases, fortified foods and dietary supplements may be useful sources of one or more nutrients that otherwise might be consumed in less than recommended amounts. However, dietary supplements, while recommended in some cases, cannot replace a healthful diet." It is important for anyone who is considering taking an iron supplement to first consider whether their needs are being met by natural dietary sources of heme and nonheme iron and foods fortified with iron, and to discuss their potential need for iron supplements with their physician.

The Dietary Guidelines for Americans describes a healthy diet as one that:

  • emphasizes a variety of fruits, vegetables, whole grains, and fat-free or low-fat milk and milk products;
  • includes lean meats, poultry, fish, beans, eggs, and nuts;
  • is low in saturated fats, trans fats, cholesterol, salt (sodium), and added sugars; and
  • stays within your daily calorie needs.

For more information about building a healthful diet, refer to the Dietary Guidelines for Americans (http://www.health.gov/dietaryguidelines/) and the U.S. Department of Agriculture's food guidance system, MyPyramid (http://www.mypyramid.gov/).

Related Links: What is iron? | What foods provide iron? | How much iron do I need? | What happens if I do not get enough iron? | Do I need extra iron? | What are some of the current issues and controversies about iron? |

Iron and Total Iron Binding Blood Test Iron and Total Iron Binding Blood Test  Iron and Total Iron Binding This test is used in the detection of anemia. TIB levels are often used to monitor the course of individuals receiving hyperalimentation.

Disclaimer

Reasonable care has been taken in preparing this document and the information provided herein is believed to be accurate. However, this information is not intended to constitute an "authoritative statement" under Food and Drug Administration rules and regulations.

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The mission of the Office of Dietary Supplements (ODS) is to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, stimulating and supporting research, disseminating research results, and educating the public to foster an enhanced quality of life and health for the U.S. population.

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Health professionals and consumers need credible information to make thoughtful decisions about eating a healthful diet and using vitamin and mineral supplements. These Fact Sheets provide responsible information about the role of vitamins and minerals in health and disease. Each Fact Sheet in this series received extensive review by recognized experts from the academic and research communities.

The information is not intended to be a substitute for professional medical advice. It is important to seek the advice of a physician about any medical condition or symptom. It is also important to seek the advice of a physician, registered dietitian, pharmacist, or other qualified health professional about the appropriateness of taking dietary supplements and their potential interactions with medications.

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Footnotes

  1. Hurrell RF. Preventing iron deficiency through food fortification. Nutr Rev 1997;55:210-22. PubMed abstract [↩]
  2. Miret S, Simpson RJ, McKie AT. Physiology and molecular biology of dietary iron absorption. Annu Rev Nutr 2003;23:283-301. [↩]
  3. U.S. Department of Agriculture, Agricultural Research Service. 2003. USDA Nutrient Database for Standard Reference, Release 16. Nutrient Data Laboratory Home Page, http://www.nal.usda.gov/fnic/foodcomp. [↩]
  4. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
  5. Bothwell TH, Charlton RW, Cook JD, Finch CA. Iron Metabolism in Man. St. Louis: Oxford: Blackwell Scientific, 1979. [↩]
  6. Miret S, Simpson RJ, McKie AT. Physiology and molecular biology of dietary iron absorption. Annu Rev Nutr 2003;23:283-301. [↩]
  7. Uzel C and Conrad ME. Absorption of heme iron. Semin Hematol 1998;35:27-34. [PubMed abstract] [↩]
  8. Sandberg A. Bioavailability of minerals in legumes. British J of Nutrition. 2002;88:S281-5. [PubMed abstract] [↩]
  9. Davidsson L. Approaches to improve iron bioavailability from complementary foods. J Nutr 2003;133:1560S-2S. [PubMed abstract] [↩]
  10. Hallberg L, Hulten L, Gramatkovski E. Iron absorption from the whole diet in men: how effective is the regulation of iron absorption? Am J Clin Nutr 1997;66:347-56. [PubMed abstract] [↩]
  11. Monson ER. Iron and absorption: dietary factors which impact iron bioavailability. J Am Dietet Assoc. 1988;88:786-90. [↩]
  12. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
  13. Bothwell TH, Charlton RW, Cook JD, Finch CA. Iron Metabolism in Man. St. Louis: Oxford: Blackwell Scientific, 1979. [↩]
  14. Monson ER. Iron and absorption: dietary factors which impact iron bioavailability. J Am Dietet Assoc. 1988;88:786-90. [↩]
  15. Tapiero H, Gate L, Tew KD. Iron: deficiencies and requirements. Biomed Pharmacother. 2001;55:324-32. [PubMed abstract] [↩]
  16. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
  17. Bothwell TH, Charlton RW, Cook JD, Finch CA. Iron Metabolism in Man. St. Louis: Oxford: Blackwell Scientific, 1979. [↩]
  18. Uzel C and Conrad ME. Absorption of heme iron. Semin Hematol 1998;35:27-34. [PubMed abstract] [↩]
  19. Sandberg A. Bioavailability of minerals in legumes. British J of Nutrition. 2002;88:S281-5. [PubMed abstract] [↩]
  20. Davidsson L. Approaches to improve iron bioavailability from complementary foods. J Nutr 2003;133:1560S-2S. [PubMed abstract] [↩]
  21. Hallberg L, Hulten L, Gramatkovski E. Iron absorption from the whole diet in men: how effective is the regulation of iron absorption? Am J Clin Nutr 1997;66:347-56. [PubMed abstract] [↩]
  22. Monson ER. Iron and absorption: dietary factors which impact iron bioavailability. J Am Dietet Assoc. 1988;88:786-90. [↩]
  23. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
  24. Hunt JR, Gallagher SK, Johnson LK. Effect of ascorbic acid on apparent iron absorption by women with low iron stores. Am J Clin Nutr 1994;59:1381-5. [PubMed abstract] [↩]
  25. Siegenberg D, Baynes RD, Bothwell TH, Macfarlane BJ, Lamparelli RD, Car NG, MacPhail P, Schmidt U, Tal A, Mayet F. Ascorbic acid prevents the dose-dependent inhibitory effects of polyphenols and phytates on nonheme-iron absorption. Am J Clin Nutr 1991;53:537-41. [PubMed abstract] [↩]
  26. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
  27. Samman S, Sandstrom B, Toft MB, Bukhave K, Jensen M, Sorensen SS, Hansen M. Green tea or rosemary extract added to foods reduces nonheme-iron absorption. Am J Clin Nutr 2001;73:607-12. [PubMed abstract] [↩]
  28. Brune M, Rossander L, Hallberg L. Iron absorption and phenolic compounds: importance of different phenolic structures. Eur J Clin Nutr 1989;43:547-57. [PubMed abstract] [↩]
  29. Hallberg L, Rossander-Hulthen L, Brune M, Gleerup A. Inhibition of haem-iron absorption in man by calcium. Br J Nutr 1993;69:533-40. [PubMed abstract] [↩]
  30. Hallberg L, Brune M, Erlandsson M, Sandberg AS, Rossander-Hulten L. Calcium: effect of different amounts on nonheme- and heme-iron absorption in humans. Am J Clin Nutr 1991;53:112-9. [PubMed abstract] [↩]
  31. Minihane AM, Fairweather-Tair SJ. Effect of calcium supplementation on daily nonheme-iron absorption and long-term iron status. Am J Clin Nutr 1998;68:96-102. [PubMed abstract] [↩]
  32. Cook JD, Reddy MB, Burri J, Juillerat MA, Hurrell RF. The influence of different cereal grains on iron absorption from infant cereal foods. Am J Clin Nutr 1997;65:964-9. [PubMed abstract] [↩]
  33. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
  34. Lynch SR, Dassenko SA, Cook JD, Juillerat MA, Hurrell RF. Inhibitory effect of a soybean-protein-related moiety on iron absorption in humans. Am J Clin Nutr 1994;60:567-72. [PubMed abstract] [↩]

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