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Iron is of great importance in human nutrition. The adult human body contains between 3-4 g of iron, of which 60-70 percent is present in the blood (Hb iron) as circulating iron, and the rest (1 to 1.5 g) as storage iron. Each gram of heamoglobin contains about 3.34 mg of iron.
Sources of iron:
There are two forms of iron, haem-iron and non-haem iron. Haem iron is better absorbed than non-haem iron. Foods rich in heam-iron are liver, meat, poultry and fish. They are not only sources of readily available iron but they also promote the absorption of non-heam iron in plant foods eaten at the same time. The iron content of milk is low in all mammalian species. Iron content of breast milk averages less than .2mg/dl, and it is well utilized.
Foods containing non-heam iron are those of vegetable origin, e.g. cereals, green leafy vegetables, legumes, nuts, oilseeds, jaggery and dried fruits. They are important sources of iron in the diets of a large majority of people. The bioavaillability of non-heam iron is poor owing to the presence of phytates, oxalates, carbonates, phosphates and dietary fibre, which interfere with iron absorption. Other foods, which inhibit iron absorption, are milk, eggs and tea.
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The Indian diet which is predominantly vegetarian contains large amounts of these inhibitors, e.g. phylates in bran, phosphates in egg yolk, tannin in tea and oxalates in vegetables. In some areas significant amounts of iron may be derived from cooking in iron vessels.
Benefits of Iron:
Iron is necessary for many functions in the body including formation of haemoglobin, brain development and function, regulation of body temperature, muscle activity and catecholamine metabolism. Lack of iron directly affects the immune system; it diminishes the number of T- cells and the production of antibodies. Besides haemoglobin, iron is a component of myoglobin, the cytochromes, catalase and certain enzyme systems.
Iron is essential for binding oxygen to the blood cells. The central function of the iron is oxygen transport and cell respiration.
Absorption: Iron is mostly absorbed from duodenum and upper small intestine in the ferrous state, according to body needs.
The rate of iron absorption is increased by many factors like iron reserves of the individual, the presence of inhibitors (e.g. phosphates) and promoters (e.g. ascorbic acid) of iron absorption and disorders of duodenum and jejunum.
Iron absorption is greater when there is an increased demand for iron, as for example during pregnancy.
The absorbed iron is transported as plasma ferritin and stored in liver, spleen, bone marrow and kidney. When red cells are broken down, the liberated iron is reutilized in the formation of new red cells.
Daily loss of iron from the body
The total daily iron loss of an adult is probably 1 mg and about 2 mg in menstruating women. Major routes of iron loss are:
- Through haemorrhages, that is wherever blood is lost, iron is lost, the causes of which may be physiological (e.g. menstruation, childbirth) or pathological (e.g. hookworms, malaria, haemorrhoids, peptic ulcer)
- Basal losses, such as excretion through urine, sweat and bile and desquamated surface cells.
- The recent widespread use of IUDs in the family planning programme is an additional cause of iron loss.
- Hormonal contraceptives on the other hand decrease menstrual blood loss by about 50 percent.
Deficiency symptoms of iron
Three stages of iron deficiency have been described:
- First stage is characterized by decreased storage of iron without any other detectable abnormalities.
- An intermediate stage of latent iron deficiency that is iron stores are exhausted, but anemia has not occurred as yet. Its recognition depends upon measurement of serum ferritin levels. This stage is the most prevalent stage in India.
- The third stage is that of overt iron deficiency when there is a decrease in the concentration of circulating haemoglobin due to impaired haemoglobin synthesis.
The end result of iron deficiency is nutritional anaemia, which is not a disease. It is rather a syndrome caused by malnutrition. Besides anaemia there may be other functional disturbances such as impaired cell mediated immunity, reduced resistance to infection, increased morbidity and mortality and diminished work performance.
Daily requirement of iron
Because of the recycling of iron, only a small amount of iron is needed by the body. In general iron requirements are greater and there is rapid expansion of tissue and red cell mass, as for example during pregnancy, childhood and adolescence
Requirement of iron for different age groups is given below in the table:
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Iron in mg that should be absorbed (daily needs) |
Infants (5-12 months)
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0.7 |
Children (1-12 years)
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1.0 |
Adolescence (13-16 years)
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1.8 (males)
2.4 (females) |
Adults, males
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0.9 |
Adults, females
Menstruation
Pregnancy (first half)
(Second half)
Lactation
Post- menopause
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2.8
0.8
3.5
2.4
0.7 |
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