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:
In hemoglobin, carrying oxygen to cells throughout the body
In myoglobin, holding oxygen within the cells, especially heart and skeletal muscle cells
Forming collagen, which is the major protein that makes up connective tissue, cartilage, and bone
Helping fight infection by synthesizing certain enzymes needed for immune function
Helping convert beta carotene to vitamin A
Helping make amino acids, which are the building blocks of protein
Aiding drug detoxification pathways in the liver
Forming part of an enzyme that is essential for the production of several neurotransmitters
Synthesizing cellular components that are important to metabolism
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.
Recommended Dietary Allowance
Adequate Intake (AI) = 0.27
Adequate Intake (AI) = 0.27
Lactation, equal to or less than 18 years
Lactation, 19-50 years
Groups of people who are susceptible to being iron deficient are:
Women of childbearing years
Infants (depending on their diet)
People with Crohn’s disease or celiac disease—Iron is absorbed from a small intestine, and diseases affecting it may lead to poor absorption from food sources.
There are no symptoms of iron deficiency unless you become anemic. If not corrected, iron deficiency can progress to anemia. Symptoms of
Fatigue: feeling tired all the time or getting tired easily with activities you used to be able to do without difficulty
Shortness of breath
Lightheadedness or dizziness, especially as you stand up
Heart palpitations: a pounding or racing heart when you exert yourself or even at rest
Pale skin, especially the pink lining to your lower eyelids, under your fingernails, or your gums
Unusual cravings for substances like ice, dirt, etc. (called pica)
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.
Other effects of too much iron include:
Damage to the liver and other tissues
Reduced ability to use other trace minerals (zinc, iodine, and selenium)
Major Food Sources
Food Sources of Mostly Heme Iron
Chicken liver, cooked
Oysters, breaded and fried
Beef, chuck, lean only, braised
Clams, breaded, fried
Beef, tenderloin, roasted
Turkey, dark meat, roasted
Beef, eye of round, roasted
Turkey, light meat, roasted
Chicken, leg, meat only, roasted
Tuna, fresh bluefin, cooked, dry heat
Chicken, breast, roasted
Halibut, cooked, dry heat
Crab, blue crab, cooked, moist heat
Pork, loin, broiled
Tuna, white, canned in water
Shrimp, mixed species, cooked, moist heat
Food Sources of Nonheme Iron
Ready-to-eat cereal, 100% iron fortified
Oatmeal, instant, fortified, prepared with water
Soybeans, mature, boiled
Beans, kidney, mature, boiled
Beans, lima, large, mature, boiled
Beans, navy, mature, boiled
Ready-to-eat cereal, 25% iron fortified
Beans, black, mature, boiled
Beans, pinto, mature, boiled
Tofu, raw, firm
Spinach, boiled, drained
Spinach, canned, drained solids
Black-eyed peas (cowpeas), boiled
Spinach, frozen, chopped, boiled
Grits, white, enriched, quick, prepared with water
Raisins, seedless, packed
Whole wheat bread
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:
Heme iron is absorbed more efficiently than nonheme iron.
Heme iron enhances the absorption of nonheme iron.
Vitamin C enhances the absorption of nonheme iron.
Some substances decrease the absorption of nonheme iron:
Oxalic acid, found in spinach and chocolate (However, oxalic acid is broken down with cooking.)
Phytic acid, found in wheat bran and beans (legumes)
Tannins, found in tea
Polyphenols, found in coffee
Note: Consuming heme iron and/or
with nonheme can help compensate for these decreases.
To increase your intake and absorption of dietary iron, try the following:
Combine heme and nonheme sources of iron.
Eat foods rich in vitamin C with nonheme iron sources. Good sources of vitamin C include:
Oranges and orange juice
Tomatoes and tomato juice
Spinach and collard greens
If you drink coffee or tea, do so between meals rather than with a meal.
Cook acidic foods in cast iron pots. This can increase iron content up to 30 times.
Please be aware that this information is provided to supplement the care
provided by your physician. It is neither intended nor implied to be a
substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER
IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the
advice of your physician or other qualified health provider prior to
starting any new treatment or with any questions you may have regarding a