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Iron (Fe) is a component of red blood cells and the muscles that assist in the transportation of oxygen throughout the body. Women lose twice as much iron as men and are more likely to be deficient, particularly during the child bearing years.
Drinking coffee within an hour of a meal can reduce iron absorption by up to 80%.
Iron is an essential for:
Iron deficiency can lead to anaemia when the iron stores in the body become depleted and hemoglobin synthesis is inhibited.
Symptoms and signs of anaemia include:
All the above are associated with decreased oxygen supply to tissues and organs. Iron also plays an important role in the immune system, people with low iron levels having lowered resistance to infection.
Research has also shown iron deficiency to be associated with impaired brain function, and iron deficiency in infants can result in impaired learning ability and behavioral problems.
Also associated with iron deficiencies are:
Iron deficiency develops gradually and usually begins with a negative iron balance, when iron intake does not meet the daily need for dietary iron. This negative balance initially depletes the storage form of iron while the blood hemoglobin level, a marker of iron status, remains normal. Iron deficiency anemia is an advanced stage of iron depletion. It occurs when storage sites of iron are deficient and blood levels of iron cannot meet daily needs. Blood hemoglobin levels are below normal with iron deficiency anemia.
Iron deficiency anemia can be associated with low dietary intake of iron, inadequate absorption of iron, or excessive blood loss. Women of childbearing age, pregnant women, preterm and low birth weight infants, older infants and toddlers, and teenage girls are at greatest risk of developing iron deficiency anemia because they have the greatest need for iron. Women with heavy menstrual losses can lose a significant amount of iron and are at considerable risk for iron deficiency.
Vitamin A helps mobilize iron from its storage sites, so a deficiency of vitamin A limits the body's ability to use stored iron. This results in an "apparent" iron deficiency because hemoglobin levels are low even though the body can maintain normal amounts of stored iron.
Chronic malabsorption can contribute to iron depletion and deficiency by limiting dietary iron absorption or by contributing to intestinal blood loss. Most iron is absorbed in the small intestines. Gastrointestinal disorders that result in inflammation of the small intestine may result in diarrhea, poor absorption of dietary iron, and iron depletion.
Dietary iron exists in two different forms. Haem iron only exists in animal tissues, whilst in plant foods iron is present as non-haem iron. In a mixed omnivore diet around 25% of dietary iron is non-haem iron. Non-haem iron is less easily absorbed by the body than is haem iron. The amount of iron absorbed from various foods ranges from around 1 to 10% from plant foods and 10 to 20% from animal foods.
The absorption of iron is influenced by other constituents of a meal. Phytates, oxalates and phosphates present in plant foods can inhibit absorption, as can tannin in tea. Fibre may also inhibit absorption. Vitamin C greatly increases the absorption of non-haem iron. Foods rich in vitamin C include citrus fruits, green peppers, and fresh leafy green vegetables. Citric acid, sugars, amino acids and alcohol can also promote iron absorption. Iron absorption can also be influenced by the amount of iron in the diet. Lowered levels of iron in the diet result in improved absorption.
Good sources of iron for vegetarians include wholegrain cereals and flours, leafy green vegetables, blackstrap molasses, pulses, such as, lentils and kidney beans, and some dried fruits.
Healthy full term infants are born with a supply of iron that lasts for 4 to 6 months.
Iron in human breast milk is well absorbed by infants. It is estimated that infants can use greater than 50% of the iron in breast milk as compared to less than 12% of the iron in infant formula. The amount of iron in cow's milk is low, and infants poorly absorb it. Feeding cow's milk to infants also may result in gastrointestinal bleeding. For these reasons, cow's milk should not be fed to infants until they are at least 1 year old.
The American Academy of Pediatrics (AAP) recommends that infants be exclusively breast fed for the first six months of life. Gradual introduction of iron-enriched solid foods should complement breast milk from 7 to 12 months of age. Infants weaned from breast milk before 12 months of age should receive iron-fortified infant formula
Total dietary iron intake in vegetarian diets may meet recommended levels; however that iron is less available for absorption than in diets that include meat. Vegetarians who exclude all animal products from their diet may need almost twice as much dietary iron each day as non-vegetarians because of the lower intestinal absorption of nonheme iron in plant foods. Vegetarians should consider consuming nonheme iron sources together with a good source of vitamin C, such as citrus fruits, to improve the absorption of nonheme iron.
Nutrient requirements increase during pregnancy to support fetal growth and maternal health. Iron requirements of pregnant women are approximately double that of non-pregnant women because of increased blood volume during pregnancy, increased needs of the fetus, and blood losses that occur during delivery. If iron intake does not meet increased requirements, iron deficiency anemia can occur. Iron deficiency anemia of pregnancy is responsible for significant morbidity, such as premature deliveries and giving birth to infants with low birth weight.
Iron supplementation is indicated when diet alone cannot restore deficient iron levels to normal within an acceptable timeframe. Supplements are especially important when an individual is experiencing clinical symptoms of iron deficiency anemia. The goals of providing oral iron supplements are to supply sufficient iron to restore normal storage levels of iron and to replenish hemoglobin deficits.
Copper, cobalt, manganese and vitamin C are required for iron to be absorbed by the body and should be taken at the same time. Only 8% of the iron taken orally is actually absorbed by the bloodstream.
Iron deficiency is uncommon among adult men and postmenopausal women. These individuals should only take iron supplements when prescribed by a physician because of their greater risk of iron overload. Iron overload is a condition in which excess iron is found in the blood and stored in organs such as the liver and heart.
Toxicity is rare but there is potential for iron toxicity because very little iron is excreted from the body. Thus, iron can accumulate in body tissues and organs when normal storage sites are full.
Doses of iron prescribed for iron deficiency anemia in adults are associated with constipation, nausea, vomiting, and diarrhea, especially when the supplements are taken on an empty stomach.
Hereditary haemochromatosis: a realistic approach to prevention of iron overload disease in the population.
Iron overload in body tissues can cause complications such as cirrhosis, cardiomyopathy, diabetes, hypogonadism and arthritis. In populations of northern European descent, most iron overload is due to hereditary haemochromatosis (HHC), a genetic condition that causes increased iron absorption. HHC can be treated or prevented by regular phlebotomy treatments (withdrawing blood, like a blood donation).
Some experts have called for population screening for HHC, so that early phlebotomy treatment can be initiated. Two screening tests are available: measurement of the serum iron transferrin saturation (Tf%) and genetic testing for HFE mutations. However, both methods have low positive predictive values. Current data suggest that most people at risk are unlikely to develop clinical symptoms and that the population prevalence of clinical complications of HHC is low, arguing against population screening.
Two other prevention strategies are available. (1) Health provider education, to heighten awareness of HHC as an explanation for symptoms and signs seen in early iron overload including unexplained fatigue, joint pain, palpitations, abdominal pain, elevated liver function tests, hepatomegaly and elevated serum ferritin. (2) Family-based testing after a diagnosis of HHC, to ensure that relatives are evaluated for evidence of iron overload. More research is also needed to identify the factors that increase risk for disease in persons with excess iron uptake, to determine whether moderate iron overload is a health risk and to evaluate the causes of iron overload other than HHC.
PMID: 12401310 [PubMed - indexed for MEDLINE]
Further details about HHC are provided in the following video, made available by the Canadian Hemochromatosis Society
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