Tartalomjegyzék
Tartalomjegyzék
Iron is critical to human life. It plays the central role in the hemoglobin molecule of red blood cells (RBC) where it functions in transporting oxygen from the lungs to the body's tissues and the transportation of carbon dioxide from the tissues to the lungs. Iron also functions in several key enzymes in energy production and metabolism including DNA synthesis.
Iron deficiency is the most common nutrient deficiency in the United States. The groups at highest risk for iron deficiency are infants under two years of age, teenage girls, pregnant women, and the elderly. Studies have found evidence of iron deficiency in as high as 30-50% of people in these groups.
Iron deficiency may be due to an increased iron requirement, decreased dietary intake, diminished iron absorption or utilization, blood loss, or a combination of factors. Increased requirements for iron occur during the growth spurts of infancy and adolescents and during pregnancy and lactation. Currently, the vast majority of pregnant women are routinely given iron supplements during their pregnancy as the dramatically increased need for iron during pregnancy cannot usually be met through diet alone.
Iron deficiency is the most common cause of anemia (deficiency of red blood cells), however, it must be pointed out that anemia is the last stage of iron deficiency. Iron-dependent enzymes involved in energy production and metabolism are the first to be affected by low iron levels. Serum ferritin is the best laboratory test for determining body iron stores.
Even marginal iron deficiency can significantly impair immune function. Iron deficiency greatly reduces the immune system ability to fight off infection. Common findings in iron-deficient individuals are increased rate of infections, lymphatic tissue shrinkage, altered white blood cell concentrations, and defective white blood cell function. Iron deficiency may be the responsible factor in many individuals suffering from impaired immune function, chronic infections, and frequent colds.
Iron deficiency is also associated with markedly decreased attentiveness; less complex or purposeful, narrower attention span; decreased persistence; and decreased voluntary activity. Fortunately, with iron supplementation there is a return to normal mental function.
In regards to energy levels, several researchers have clearly demonstrated that even a slight iron-deficiency leads to a reduction in physical work capacity and productivity.
Nutrition surveys done in the U.S. have indicated that iron-deficiency is a major impairment of health and work capacity and as a consequence of this an economic loss to the individual and the country. Supplementation with iron has shown rapid improvements in work capacity in iron-deficient individuals. Impaired physical performance due to iron deficiency is not dependent on anemia. Again, the iron-dependent enzymes involved in energy production and metabolism will be impaired long before anemia occurs.
Women typically lose 40 to 80 ml of blood per period. Heavier periods are definitely associated with negative iron balance in most cases. Negative iron balance means that more blood is lost than is being absorbed from the diet.
Menstrual blood loss is well recognized as a major cause of iron deficiency anemia in fertile women. However, what is not as well known that chronic iron deficiency can be a cause of excessive menstrual blood loss a condition known as menorrhagia. It has been suggested that iron deficiency leads to menorrhagia based on several observations with the most important being that iron supplementation often produces a dramatic decrease in menstrual blood loss. In one double-blind placebo-controlled study 75% of those on iron supplementation had significant reduction of menorrhagia compared with only 32.5% for the placebo group.
Iron supplementation, at a daily dose of 100 mg elemental iron, has been recommended as a preventive therapy by several researchers, since it appears that chronic iron deficiency may promote menorrhagia, and iron-containing enzymes in the uterus are depleted before changes in red blood cell numbers or hemoglobin are observed.
During pregnancy, the requirement for iron increases dramatically due to iron contributions to the fetus, placenta, and umbilical cord coupled with an increase in red cell mass in the mother. Iron loss in the urine, sweat and feces is also increased. Subsequently, anemia due to iron deficiency is extremely common in pregnancy. For these reasons the recommended daily intake of iron during pregnancy is 60 mg. Since this typically cannot be achieved by dietary means supplementation is required.
The need for additional iron is not over when the baby is delivered. Typically the mother will lose approximately 150 to 300 mg. of iron due to hemorrhage and blood loss during delivery. In addition, lactation causes an additional drain of iron stores. For these reasons it is important for women to continue to take iron supplements throughout their pregnancy and nursing period.
Even marginal iron deficiency can significantly impair immune function. Iron deficiency greatly reduces the immune system ability to fight off infection. Common findings in iron-deficient individuals are increased rate of infections, lymphatic tissue shrinkage, altered white blood cell concentrations, and defective white blood cell function. Iron deficiency may be the responsible factor in many individuals suffering from impaired immune function, chronic infections, and frequent colds.
Several researchers have clearly demonstrated that even a slight iron-deficiency leads to a reduction in physical work capacity and productivity. Nutrition surveys done in the U.S. have indicated that iron-deficiency is a major impairment of health and work capacity and as a consequence of this an economic loss to the individual and the country. Supplementation with iron has shown rapid improvements in work capacity in iron-deficient individuals. Impaired physical performance due to iron deficiency is not dependent on anemia. Again, the iron-dependent enzymes involved in energy production and metabolism will be impaired long before anemia occurs.
Virtually any nutrient deficiency can result in impaired brain function, especially in children. Since iron deficiency is the most common nutrient deficiency in American children, it is the most important nutritional cause of learning disability. Iron deficiency is associated with markedly decreased attentiveness; less complex or purposeful, narrower attention span; decreased persistence; and decreased voluntary activity. Fortunately, with iron supplementation there is a return to normal mental function.
Low serum iron or ferritin levels have been found in patients with the so-called "restless legs syndrome" (RLS) – the syndrome characterized by an irresistible urge to move the legs. In individuals with RLS and low serum ferritin levels, iron supplementation has been shown to significantly improve RLS.
The most popular iron supplements are ferrous sulfate and ferrous fumarate. However, the best forms appear to be ferric pyrophosphate and ferrous bisglycinate. Both are free from gastrointestinal side effects with a higher relative bioavailability especially if taken on an empty stomach.
For iron deficiency, the usual recommendation is 30 mg of iron twice daily between meals. If this recommendation results in abdominal discomfort, take 30 mg with meals three times daily.
The most common side effects are mild gastrointestinal irritation, constipation or diarrhea, and nausea. These are most often seen with ferrous sulfate or fumarate. Ferric pyrophosphate and ferrous bisglycinate are better tolerated.
Recent studies have suggested the possible role of elevated iron levels and the risk for heart attacks. Elevated levels of iron in the blood may lead to an increased risk of heart disease by spinning off free radicals in the blood and either damaging cholesterol or the artery walls directly. For these reasons, many experts believe that it is best to reserve iron supplementation to cases of iron deficiency, menstruating women, and during pregnancy and lactation.
Anti-inflammatory drugs like aspirin and ibuprofen may contribute to iron loss via gastrointestinal bleeding.
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