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Iron is essential to nearly all known organisms. In cells, iron is generally stored in the centre of metalloproteins, because "free" iron -which binds non-specifically to many cellular components - can catalyses production of toxic free radicals. Iron has several vital functions in the body. It serves as a carrier of oxygen to the tissues from the lungs by red blood cell hemoglobin, as a component of hemoglobin and myogloin iron is required for O2 and CO2 transport. In cytochromes and nonheme iron proteins it is required for oxidative phosphorylation and in the lysosomal enzyme- myeloperoxidase -, it is required for phagocytosis and killing of bacteria by neutrophils. Most of the iron in the body is present in the erythrocytes as hemoglobin, a molecule composed of four units, each containing one heme group and one protein chain. The structure of hemoglobin allows it to be fully loaded with oxygen in the lungs and partially unloaded in the tissues (e.g. in the muscles). The newborn term infant has an iron content of about 250–300mg (75mg/kg body weight).
During the first 2 months of life, hemoglobin concentration falls because of the improved oxygen situation in the newborn infant compared with the intrauterine fetus. This leads to a considerable redistribution of iron from catabolized erythrocytes to iron stores. Because of the marked supply of iron to the fetus during the last trimester of pregnancy, the iron situation is much less favorable in the premature and low-birth-weight infant than in the healthy term infant. An extra supply of iron is therefore needed in these infants during the first 6 months of life. Populations most at risk for iron deficiency are infants, children, adolescents, and women of childbearing age, especially pregnant women. Assuming a 10-15% efficiency of absorption, an RDA of 8mg /day for normal adult males and 18 mg/day for menstruating females has been set.
For pregnant females it is 27 mg per day .While 8 mg per day of iron can easily be obtained from a normal diet. The best known symptom of iron deficiency is a microcytic hypochromic anemia. Iron deficiency is also associated with decrease immunocompetence. Dietary surveys indicate that 95% or more of children and menstruating females do not obtain adequate dietary iron. Biochemical measurements reveals 10-25% incidence of iron deficiency anemia in this same group. Iron deficiency anemia is also problem with a elderly due to poor dietary intake and increased frequency of achlorhydria. Because iron deficiency anemia is widespread, government programs of nutritional intervention such as the WIC program have emphasized iron reach foods. However, since recent studies have suggested that access iron intake may increase the risk of cardiovascular disease, iron supplementation and the consumption of iron fortified foods may be inappropriate for adult men and post menopausal women. lack of iron-containing enzymes which are rate limiting for oxidative metabolism may cause oxidative stress in body. Further to this, several groups have observed a reduction in physical working capacity in human populations with longstanding iron deficiency, and demonstrated an improvement in working capacity in these populations after iron administration.
The relationship between iron deficiency and brain function and development is very important to consider when choosing a strategy to combat iron deficiency. Several structures in the brain have high iron content; levels are of the same order of magnitude as those observed in the liver. The observation that the lower iron content of the brain in iron-deficient growing rats cannot be increased by giving iron at a later date strongly suggests that the supply of iron to brain cells takes place during an early phase of brain development and that, as such, early iron deficiency may lead to irreparable damage to brain cells. Iron deficiency also negatively influences the normal defense systems against infections. In animal studies, the cell-mediated immunologic response by the action of T-lymphocytes is impaired as a result of a reduced formation of these cells. This in turn is due to a reduced DNA synthesis dependent on the function of ribonucleotide reductase, which requires a continuous supply of iron for its function.
In addition, the phagocytosis and killing of bacteria by the neutrophil leukocytes is an important component of the defense mechanism against infections. These functions are impaired in iron deficiency as well. Several groups have demonstrated a relationship between iron deficiency and attention, memory, and learning in infants and small children. Therapy resistant behavioral impairment and the fact that there is an accumulation of iron during the whole period of brain growth should be considered strong arguments for the early detection and treatment of iron deficiency. This is valid for women, especially during pregnancy, and for infants and children, up through the period of adolescence to adulthood. In a recent well controlled study, administration of iron to non-anemic but iron-deficient adolescent girls improved verbal learning and memory. Well-controlled studies in adolescent girls show that iron-deficiency without anemia is associated with reduced physical endurance and changes in mood and ability to concentrate. Another recent study showed that there was a reduction in maximum oxygen consumption in non-anemic women with iron deficiency that was unrelated to a decreased oxygen transport capacity of the blood.
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