IRON

The following health problems and diseases may be prevented through the treatment or prevention of iron deficiency.

Impaired intellectual development in children

Most observational studies have found relationships between iron deficiency anemia in children and poor cognitive development, poor school achievement, and behavior problems. However, it is difficult to separate the effects of iron deficiency anemia from other types of deprivation in such studies. In anemic children under the age of 2 years, only one randomized double blind trial found a significant benefit of iron supplementation on indices of cognitive development. However, 4 randomized controlled trials found a significant benefit of iron supplementation on cognition and school achievement in children over 2 years of age, while 2 studies found no effect. Several possible mechanisms link iron deficiency anemia to altered cognition. Anemic children tend to move around and explore their environment less than children without anemia, which may lead to developmental delays. Conduction of auditory and optic nerve impulses to the brain has been found to be slower in children with iron deficiency anemia. This effect could be associated with changes in nerve myelination, which have been observed in iron deficient animals. Neurotransmitter synthesis may also be sensitive to iron deficiency.

Lead toxicity

Iron deficiency may increase the risk of lead poisoning in children. A number of epidemiologic studies have found iron deficiency to be associated with increased blood lead levels in young children. Iron deficiency and lead poisoning share a number of the same risk factors, but iron deficiency has been found to increase the intestinal absorption of lead in humans and animals. However, the use of iron supplementation in lead poisoning should be reserved for those individuals who are truly iron deficient or for those individuals with continuing lead exposure, such as continued residence in lead-exposed housing.

Pregnancy complications

Epidemiologic studies provide strong evidence of an association between severe anemia in pregnant women and adverse pregnancy outcomes, such as low birth weight, premature birth, and maternal mortality. Iron deficiency can be a major contributory factor to severe anemia, but evidence that iron deficiency anemia is a causal factor in poor pregnancy outcomes is still lacking. Nevertheless, most experts consider the control of maternal anemia to be an important part of prenatal health care. Elevated hemoglobin, especially in later pregnancy, is also associated with poor pregnancy outcomes, but there is no evidence that this association is related to high iron intakes or iron supplementation. Rather, elevated hemoglobin in pregnancy is more likely to be explained by underlying conditions like pregnancy induced hypertension or preeclampsia, which are well known to contribute to poor pregnancy outcomes.

Impaired immune function

Iron is required by most infectious agents, as well as by the infected host in order to mount an effective immune response. Sufficient iron is critical to several immune functions, including the differentiation and proliferation of T lymphocytes and the generation of reactive oxygen species (ROS) by iron-dependent enzymes, which are used for killing pathogens. During an acute inflammatory response, serum iron levels decrease while levels of ferritin (the iron storage protein) increase, suggesting that sequestering iron from pathogens is an important host response to infection. Despite the critical functions of iron in the immune response, the nature of the relationship between iron deficiency and susceptibility to infection, especially with respect to malaria, remains controversial. High-dose iron supplementation of children residing in the tropics has been associated with increased risk of clinical malaria and other infections, such as pneumonia. Studies in cell culture and animals suggest that the survival of infectious agents that spend part of their life cycle within host cells, such as plasmodia (malaria) and mycobacteria (tuberculosis) may be enhanced by iron therapy. Controlled clinical studies are needed to determine the appropriate use of iron supplementation in regions where malaria is common, as well as in the presence of infectious diseases, such as HIV, tuberculosis, and typhoid.

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