Iron is a critical mineral in the body. Iron is required to transport oxygen from the lungs to the cells in the body and for oxygen storage in the muscles. And, although iron is one of the most abundant elements on earth, it is also one of the most frequently observed deficiencies in the world. According to the Centers for Disease Control and Prevention, the prevalence of iron deficiency in the U.S. is about 2 percent in adult men, 9 to 12 percent in non-Hispanic white women and nearly 20 percent in black and Mexican-American women.
There are two forms of iron in the diet: heme and nonheme. In foods from animal sources, such as meat, poultry and fish, about half the iron is heme iron and the rest is nonheme. Iron from dairy foods, eggs and plant-based foods is entirely nonheme. Iron is better absorbed by the body from heme sources. Vitamin C also improves absorption of both forms of iron when consumed at the same meal. Fortified products, such as breads, cereals and breakfast bars, can contribute significant amounts of nonheme iron to the diet. For example, some fortified cereals can contain up to 24 mg of iron per 1-cup serving.
Inadequate dietary iron results in iron deficiency anemia, the most common nutritional deficiency in the world. Symptoms include fatigue, reduced cognitive function, increased risk of infection and delayed development in infants. Iron deficiency anemia can also be the result of impaired iron absorption or iron loss due to blood loss from menstruation, injury and gastrointestinal bleeding. Iron deficiency is more common among infants, toddlers, teenage girls, women of childbearing age and vegetarians. Iron intake requirements are 1.8 times higher for vegetarians because nonheme iron is not absorbed as well as heme iron.
It’s not likely that you’ll get too much iron from dietary sources. However, high doses from supplements could cause harmful effects, ranging from gastrointestinal effects, such as nausea, vomiting and diarrhea, to cardiovascular, nervous system, kidney and liver effects. Children should never be given iron supplements unless under the guidance of a physician or qualified health professional. Iron toxicity (from high doses of supplements) in children can rapidly result in severe long-term effects or death.
People with the following conditions may be at risk of harmful effects due to high iron intakes and therefore should not consume excess amounts of iron: hereditary hemochromatosis (a condition that causes the body to absorb and store too much iron), chronic alcoholism, liver disease, iron-loading abnormalities and certain genetic disorders. Additionally, it is recommended that adult men and postmenopausal women avoid iron supplements and highly fortified foods because of their greater risk for iron overload, a condition that leads to iron accumulation in the body.
The following table lists the recommended intake for healthy people based on current scientific information.