Iron

Iron deficiency, the precursor of iron deficiency anemia, is the most common of all nutritional deficiency diseases. In the United States and worldwide, iron deficiency anemia is prevalent among children and woman of childbearing age. The groups considered to be at greatest risk for iron deficiency anemia are infants younger than 2 years of age, adolescent girls, pregnant woman, and older adults. Pregnant teenagers are frequently at high risk because of poor eating habits and continuing growth. Women in their childbearing years who are iron deficient benefit from either a diet rich in iron-containing foods or supplements. 

Nutritional iron deficiency and iron deficiency anemia remain far too common in our days given the wide availability of iron-rich foods. Iron deficiency anemia is the world’s most common nutritional deficiency disease. The adult human body contains iron in two major pools: functional iron in hemoglobin, myoglobin and enzymes; and storage iron in ferritin, hemosiderin and transferrin (a transport protein in blood). Healthy adult men have about 3.6 g of total body iron, whereas women have about 2.4 g. Iron is highly conserved by the body; approximately 90% is recovered and reused every day. The rest is excreted, primarily in the bile. Dietary iron must be available to maintain iron balance to meet this 10% gap, or iron deficiency results.

Two concerns about iron nutritional status predominate: the incidence of iron deficiency anemia and the role of excessive iron intake in coronary heart disease and cancer. Because of food fortification and the use of iron supplements by so many individuals, high iron intakes by men and postmenopausal women may be contributing to the risk of these chronic diseases. A study of older adults replete with iron that increased iron stores were a liability. Iron supplements may not be beneficial for either older women or older men because of the associated increased risks for heart disease and cancer. 

An adequate iron intake is essential for the normal function of the immune system. Iron overloads and deficiencies result in changes in the immune response. Iron is required by bacteria; therefore an iron overload may result in an increased risk of infection. Iron deficiency affects humoral and cellular immunity. Concentrations of circulating T-lymphocytes decrease in individuals with an iron deficiency, and the mitogenic response is typically impaired. Natural killer cell activity also decreases.

The availability of iron derived from food is important in the consideration of dietary sources. Only 50% or less of the iron in whole grain cereals and in some green vegetables is available in a usable form. Vegetarian or vegan women can obtain enough iron from their plant-based diet, but they must consume sufficient amounts of moderately iron-rich foods, such as legumes and dried fruits. Soy products are typically good sources of iron and zinc.

Female athletes, especially cross-country runners and others involved in endurance sports, often have an iron deficiency at some point in their training (iron losses occurring through the gut may increase during the stressful conditions of training) if they are not taking iron supplements or do not have diets high in iron. 

Iron deficiency can be caused by injury, hemorrhage, or illness. Iron deficiency may also be aggravated by an unbalanced diet containing insufficient iron, protein, folate, and vitamin C. Anemia typically develops because of an inadequate amount of dietary iron or faulty iron absorption.

To prevent worsening of the iron deficiency, individuals should be counseled regarding a diet that is appropriately rich in iron.

Dietary reference intake

Infants 7-11 mg/day

Children 8-10 mg/day

Adolescents 10-15 mg/day

Adults 8-18 mg/day

Pregnant 27 mg/day

Lactating 9-10 mg/day

Iron content of selected foods

Cereal, ready to eat, fortified, 1 cup (1-22 mg)

Clams, canned 3 oz (24 mg)

Beef liver, cooked, 1 piece (295 g) – (19 mg)

Beef, top sirloin, cooked, 3 oz – (17 mg)

Rice, white, enriched, 1 cup (10 mg)

Chicken liver, cooked, 100 g – (9 mg)

Baked beans, 1 cup (8 mg)

Spinach, cooked, 1 cup (6.43 mg)

Bagel, enriched, 1 (5.4 mg)

Rabbit, cooked, 3 oz (4 mg)

Deficiency

Hypochromic microcytic anemia

Feeling tired and weak

Shortness of breath (dyspnoea)

Changes in your appearance, such as a pale complexion and dry nails

Slow cognitive and social development during childhood

Difficulty maintaining body temperature

Decreased immune function, which increases susceptibility to infection

Glossitis (an inflamed tongue)

Toxicity

Hereditary hemochromatosis

Thalassemia

Hemosiderosis