Iron is a metal that is essential for life. It is a part of proteins and enzymes found throughout your body, including hemoglobin and myoglobin, both of which help carry oxygen in the blood. Iron is an important component of your muscles, and it helps regulate the growth of cells. Iron comes from foods you eat and any excess iron is stored for future use.
Iron in foods comes in two forms: heme and nonheme. Heme iron is found in animal foods that originally contained hemoglobin and myoglobin, such as red meat, fish and poultry. Nonheme iron is found in plants, such as lentils and other beans. Nonheme iron is the form of iron added to iron-enriched and iron-fortified foods.
Healthy adults absorb about 10 to 15 percent of the iron in foods, but several factors can affect the actual amount absorbed. One factor is the type of iron. Heme iron is absorbed more efficiently than nonheme (up to 35 percent is absorbed) and its absorption is not affected by other nutrients in food. From 2 to 20 percent of nonheme iron is absorbed from food. These nutrients decrease the amount of nonheme absorbed: tannins (found in tea), calcium, polyphenols, phytates (found in legumes and whole grains), and some soybean proteins. Adding meat and vitamin C to your meals will improve the absorption of nonheme iron.
Another factor that affects absorption of iron from food is the amount of iron stored in your body. If you have enough iron stored, you absorb less from food. This protects you from the toxic effects of too much iron.
How much iron?
The dietary reference intake (DRI) for iron for healthy adults is based on your age and gender. Menstruating women need more iron because some iron is lost in menstrual periods. Women who are breastfeeding also need slightly more iron. Pregnant women need about twice the daily iron as women who aren't pregnant. If you are pregnant, follow your health care provider's recommendation on iron intake.
DRI for iron for children and adults
9 to 13 years
14 to 18 years
19 to 50 years
Source: Office of Dietary Supplements, National Institutes of Health
If you don't get enough iron from the food you eat, your body will use the iron it has stored. If your diet continues to be deficient in iron, your body will eventually use up all the stored iron, and it won't be able to maintain hemoglobin at a normal level. This condition is called iron deficiency anemia. Other factors that can lead to iron deficiency anemia are heavy menstrual blood flow, kidney failure, a deficiency of vitamin A (which helps your body extract stored iron), and certain gastrointestinal disorders that interfere with absorption of iron from food. Healthy adult men and postmenopausal women normally don’t lose much iron and have a low risk for iron deficiency. Some medications can decrease iron levels. These include ACTH (a hormone), colchicine, deferoxamine, methicillin, and testosterone.
People who regularly engage in intense exercise—female athletes, distance runners, vegetarian athletes—may need 30 percent more iron than normal. If you are an athlete, you should talk to your health care provider about the need for extra iron.
Symptoms of iron deficiency include:
Symptoms of long-term iron deficiency include a burning sensation in the tongue, or a smooth tongue; sores at the corners of the mouth; pica (cravings for a specific nonfood substances, such as licorice, chalk, or clay); and spoon-shaped fingernails and toenails.
If your diet can't restore iron levels to normal within an acceptable time, you may need an iron supplement (ferrous or ferric). Ferrous iron salts (ferrous fumarate, ferrous sulfate, and ferrous gluconate) are the best absorbed forms of iron supplements. If you need an iron supplement, your health care provider can determine how much you should take and for how long. Your provider may monitor your blood levels of hemoglobin and ferritin, and the level of newly formed red blood cells to determine how long a supplement should be taken. Iron supplements may cause gastrointestinal side effects such as nausea, vomiting, constipation, diarrhea, dark colored stools, and/or abdominal distress.
It is important to keep iron supplements tightly capped and away from children. Even 200 mg of iron may be fatal in children. Call your health care provider, poison control center or emergency room immediately if you suspect a child has taken an excess amount of iron.
Iron overload is a condition in which excess iron is found in the blood and stored in organs such as the liver and heart. It is associated with several genetic diseases, including hemochromatosis, one of the most common genetic disorders in the United States. In hemochromatosis, iron is absorbed very efficiently, which can lead to a buildup of excess iron; excess iron can cause organ damage, including cirrhosis of the liver and heart failure. Symptoms of hemochromatosis rarely appear before adulthood, and it is often not discovered until organ damaged has occurred. Taking an iron supplement may speed up the effects of hemochromatosis; for this reason, adult men and postmenopausal women who are not iron deficient should avoid iron supplements. People who have sickle cell disease, myelodysplastic syndrome, or thalassemia require frequent blood transfusions, which can put them at risk of iron overload. These people are usually advised to avoid iron supplements. Certain medications, such as methyldopa and chloramphenicol, can increase iron levels.
Joint pain often occurs as iron accumulates in the body. Other symptoms include a lack of energy, weakness, weight loss, abdominal pain, loss of sex drive, and heart problems. Some people have no symptoms. Organ damage from iron overload can include liver disease (an enlarged liver, cirrhosis, cancer, or liver failure); damage to the pancreas, possibly causing diabetes; heart abnormalities, such as irregular heart rhythms or congestive heart failure; impotence; thyroid deficiency; and damage to the adrenal gland.
Treatment for iron overload includes stopping iron supplements; reducing iron levels by removing blood on a periodic basis; or using iron-chelating medication (drugs that combine with iron in the bloodstream so it can be removed from the body). In November 2005, the FDA approved Exjade (deferasirox), the first oral drug to treat chronic iron overload caused by multiple blood transfusions.
Iron toxicity, a condition in which iron accumulates to toxic levels in the body tissues and organs, can be life-threatening. People with hemochromatosis are at risk for developing iron toxicity because of their high iron stores. People who take iron supplements, have alcoholic cirrhosis, or have frequent blood transfusions also are at higher risk.
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