Iron (Fe) is a component of hemoglobin, myoglobin, and many enzymes in the body. Heme iron, contained mainly in animal products, is absorbed much better than nonheme iron (eg, in plants and grains), which accounts for > 85% of iron in the average diet. However, absorption of nonheme iron is increased when it is consumed with animal protein and vitamin C.
(See also Overview of Mineral Deficiency and Toxicity.)
Iron deficiency is one of the most common mineral deficiencies in the world. It may result from the following:
Inadequate iron intake, common in infants, adolescent girls, and pregnant women
Malabsorption (eg, celiac disease)
Chronic bleeding, including heavy menses and bleeding from gastrointestinal lesions (eg, tumors)
Chronic bleeding due to colon cancer is a serious cause in middle-aged people and the elderly.
When deficiency is advanced, microcytic anemia develops.
In addition to anemia, iron deficiency may cause pica (a craving for nonfoods) and spoon nails and is associated with restless leg syndrome. Rarely, iron deficiency causes dysphagia due to postcricoid esophageal web.
Diagnosis of iron deficiency involves complete blood count, serum ferritin and iron levels, and possibly measurement of transferrin saturation (iron-binding capacity). In deficiency states, iron and ferritin levels tend to be low, and iron-binding capacity tends to be high.
Rarely, when the diagnosis of iron deficiency remains uncertain, examination of bone marrow for iron may be necessary.
Treatment of iron deficiency involves correcting the cause if possible (eg, treatment of a bleeding intestinal tumor). All people with moderate or severe iron deficiency and some people with mild deficiency require iron supplementation.