Anemia is a condition in which too few red blood cells are in circulation. Because red blood cells are responsible for carrying oxygen to the organs and cells of the body, a deficiency of red blood cells can be life-threatening.

Iron is a central component of red blood cells, and iron deficiency is the most frequent cause of anemia. It results from inadequate levels of iron in the body, causing decreased production of red blood cells.

The most common cause of iron deficiency is blood loss, usually through excessive menstrual flow or gastrointestinal bleeding. The condition may also be caused by inadequate iron intake, increased iron usage by the body due to rapid growth (as in infancy, adolescence, and pregnancy), poor absorption (e.g., celiac disease or previous stomach surgery, including "stomach stapling" procedures), blood draws, and other instances. Once the body uses up its stores of iron, anemia develops.

Iron deficiency is common in developing countries. In industrialized countries, the prevalence of iron deficiency is lower-roughly 20 percent, in some estimates-due partly to iron fortification of grain products. According to the Centers for Disease Control and Prevention (CDC), an estimated 7 percent of toddlers, 4 to 5 percent of children, 9 to 16 percent of menstruating females, and 2 percent of pubescent and adult males have iron deficiency.

Symptoms

Common symptoms include: 

• Weakness
• Fatigue
• Irritability
• Mood swings
• Headache
• Decreased appetite (especially in children)
• Pale or bluish discoloration of the skin (in dark-pigmented persons, this may be seen in the eyes or palms)
• Shortness of breath

Iron Deficiency Anemia: Risk Factors, Diagnosis, and Treatment

Risk Factors

• Age: Children have a greater risk of iron deficiency anemia due to rapid growth, particularly in the first two years of life.
• Gender: Women generally consume less iron than men and may have a greater need for iron, depending on their stage of life. On average, a menstruating woman loses 30 to 45 milligrams of iron per month. Pregnancy and delivery together use about 1 gram of maternal iron. Breast-feeding a child uses a total of about 1 gram of maternal iron in the first year of life.
• Peptic ulcer disease and gastritis: These disorders lead to blood loss, which can deplete iron stores. Aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) are often contributing factors.
• Cancer: Esophageal, gastric, and other gastrointestinal cancers often cause occult bleeding.
• Excessive exercise: Rarely, blood losses may occur due to intense exercise. Iron losses also result from increased sweating. In particular, such losses may predispose adolescent female athletes to anemia.
• Dietary factors (see Nutritional Considerations).

Diagnosis

• A careful history and physical examination, including dietary and menstrual history, are essential.
• Simple blood tests can accurately assess a person's iron status.
• Bone marrow biopsy to determine marrow iron stores was a standard means of diagnosis in the past, but this procedure is now only rarely necessary.

Treatment

Treatment involves resolving the patient's iron deficiency, as well as addressing the underlying cause (e.g., ulcer, malignancy, excess menstrual flow, dietary deficiency, iron malabsorption).

• Ferrous sulfate is most commonly used oral iron supplement and has the greatest bioavailability, but it may also lead to more stomach upset than other forms of iron. Typical adult dosage is 325 milligrams of ferrous sulfate taken up to three times daily.
• Dairy products should be avoided because they interfere with the absorption of oral iron (see Nutritional Considerations). Supplements should be taken on an empty stomach, if tolerated, and at least two hours before, or four hours after, antacids.
• Simultaneous intake of vitamin C (ascorbic acid) increases absorption of iron. A glass of orange juice contains sufficient vitamin C to significantly increase iron absorption from foods.
• If oral supplements are not sufficient, intramuscular iron shots and intravenous iron treatments are available.

Iron Deficiency Anemia: Nutritional Considerations

Dietary iron is available in two forms: heme and nonheme. Heme iron is found in animal muscle and blood, whereas nonheme iron is found both in animal products and in a variety of plant-based foods.

Heme iron in the diet is absorbed at a relatively constant rate of about 23 percent, independent of other dietary factors. On the other hand, nonheme iron absorption varies, depending on other dietary factors, as described below.

• Healthful sources of iron include greens and legumes.
  Although the myth persists that meat is a preferred iron source, a balanced vegetarian diet that includes legumes, fortified grains, and green vegetables easily provides adequate iron. Studies have shown that the incidence of iron deficiency anemia is not greater among individuals consuming a healthy vegetarian diet than among those who eat meat. On the contrary, vegetarians get adequate iron, without the animal fat and cholesterol found in animal-based iron sources.
• Dairy products and eggs decrease iron absorption. Milk and certain forms of calcium inhibit iron absorption. Eggs (especially yolks) also appear to inhibit iron absorption. In addition, infants who are allergic to cow's milk may be particularly at risk for poor iron levels.
  
  One study showed that iron level was inversely associated with greater consumption of dairy products in toddlers; that is, those who consumed the most dairy had the lowest iron levels, and vice versa.
• Fruits and vegetables aid the absorption of nonheme iron. Fruits and vegetables contain vitamin C and organic acids (e.g., citric acid) that improve absorption of nonheme iron. Vitamin A and carotenoids also appear to enhance iron absorption. Adding vitamin A to an iron supplement regimen has also been shown to result in fewer cases of anemia than supplementation with iron alone.
• Tea, coffee, and cocoa should not be consumed with meals in patients with iron deficiency anemia. Polyphenols in these beverages inhibit the absorption of nonheme iron. Black tea appears to be the most potent in this regard.
• Taking in adequate iron before pregnancy can help prevent anemia in both mothers and infants. Iron deficiency is more common in women of child-bearing age, especially during pregnancy. The body's need for iron increases almost 10-fold during pregnancy and breast-feeding, and iron deficiency in the first trimester results in significantly poorer fetal growth, nerve development, and behavior in offspring, compared with what happens when mothers have adequate iron. In mothers with iron deficiency, exclusive breast-feeding often results in iron deficiency in infants. Without adequate iron stores before conception, iron supplementation may be necessary during pregnancy (see below).
• Breast milk contains significant iron. Human milk and cow's milk contain similar concentrations of iron (0.5 milligrams/100 milliliter, although breast-feeding is preferable for many reasons.
  
  Unfortified infant formula contains about 20 percent of the iron found in breast milk, whereas fortified formula has over twice the iron concentration. Despite this higher level, iron in breast milk is more absorbable than that in soy- or dairy-based formulas.
• Iron supplementation is not recommended for people who are not iron deficient. The CDC recommends that iron supplementation be individualized based on measured iron levels. In particular, iron supplementation should be avoided in individuals with normal iron levels, because excess iron is associated with greater risks for colon cancer, coronary heart disease, and insulin resistance. In much of the modern world, more people are at risk of having too much iron, rather than too little iron.
• Alcohol intake enhances iron absorption, but should not be used as a means of regulating iron status. Consumption of any amount of alcohol is associated with a reduction in the risk of iron deficiency anemia. However, increasing alcohol consumption is obviously not a recommended treatment for improving a person's iron levels.