Iron – Dietary Forms

Iron, one of the most abundant metals on Earth, is essential to most life forms and to normal human physiology. Iron is an integral part of many proteins and enzymes that maintain good health. In humans, iron is an essential component of proteins involved in oxygen transport.It is also essential for the regulation of cell growth and differentiation. A deficiency of iron limits oxygen delivery to cells, resulting in fatigue, poor work performance, and decreased immunity. On the other hand, excess amounts of iron can result in toxicity and even death.

  • Almost two-thirds of iron in the body is found in hemoglobin, the protein in red blood cells that carries oxygen to tissues.
  • Smaller amounts of iron are found in myoglobin, a protein that helps supply oxygen to muscle, and in enzymes that assist biochemical reactions.
  • Iron is also found in proteins that store iron for future needs and that transport iron in blood. Iron stores are regulated by intestinal iron absorption.

Forms of dietary iron

  1. Heme iron and
  2. Non heme iron
  • Heme iron is derived from hemoglobin, the protein in red blood cells that delivers oxygen to cells.Heme iron is found in animal foods that originally contained hemoglobin, such as red meats, fish, and poultry.
  • Iron in plant foods such as lentils and beans is arranged in a chemical structure called nonheme iron . This is the form of iron added to iron-enriched and iron-fortified foods.

Heme iron is absorbed better than non heme iron, but most dietary iron is non heme iron . Iron absorption Iron absorption refers to the amount of dietary iron that the body obtains and uses from food. Healthy adults absorb about 10% to 15% of dietary iron, but individual absorption is influenced by several factors .Iron absorption is also influenced by the type of dietary iron consumed. Absorption of heme iron from meat proteins is efficient. Absorption of heme iron ranges from 15% to 35%, and is not significantly affected by diet . In contrast, 2% to 20% of nonheme iron in plant foods such as rice, maize, black beans, soybeans and wheat is absorbed. Nonheme iron absorption is significantly influenced by various food components.

  1. Meat proteins and vitamin C will improve the absorption of nonheme iron.
  2. Tannins (found in tea), calcium, polyphenols, and phytates (found in legumes and whole grains) can decrease absorption of nonheme iron.
  3. Some proteins found in soybeans also inhibit nonheme iron absorption.
  4. It is most important to include foods that enhance nonheme iron absorption when daily iron intake is less than recommended, when iron losses are high (which may occur with heavy menstrual losses), when iron requirements are high (as in pregnancy), and when only vegetarian nonheme sources of iron are consumed.

Storage levels of iron have the greatest influence on iron absorption. Iron absorption increases when body stores are low. When iron stores are high, absorption decreases to help protect against toxic effects of iron overload. Recommended intake for iron

  • Man (sedentary, moderate, heavy worker)- 28 mg/day
  • Woman( sedentary, moderate, heavy worker)- 30 mg/day
  • Children(1-3yrs.)- 12mg/day,(4-6yrs.)- 18mg/day,(7-9 yrs.)- 26 mg/day
  • Boys (10-12 yrs.) -34mg/day, (13-15 yrs.)- 41 mg/day, (16-18yrs.)- 50mg/day
  • Girls (10-12 yrs.) -19mg/day, (13-15 yrs.)- 28 mg/day, (16-18yrs.)- 30mg/day

Iron supplementsThree groups of people are most likely to benefit from iron supplements:

  1. people with a greater need for iron,
  2. individuals who tend to lose more iron, and
  3. people who do not absorb iron normally.

These individuals include :

  • pregnant women
  • preterm and low birth weight infants
  • older infants and toddlers
  • teenage girls
  • women of childbearing age, especially those with heavy menstrual losses
  • people with renal failure, especially those undergoing routine dialysis
  • people with gastrointestinal disorders who do not absorb iron normally

Some facts about iron supplements Iron supplementation is indicated when diet alone cannot restore deficient iron levels to normal within an acceptable time frame. 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. When hemoglobin levels are below normal, physicians often measure serum ferritin, the storage form of iron. A serum ferritin level less than or equal to 15 micrograms per liter confirms iron deficiency anemia in women, and suggests a possible need for iron supplementation. Supplemental iron is available in two forms:

  1. ferrous iron and
  2. ferric iron

Ferrous iron salts (ferrous fumarate, ferrous sulfate, and ferrous gluconate) are the best absorbed forms of iron supplements . Elemental iron is the amount of iron in a supplement that is available for absorption. The amount of iron absorbed decreases with increasing doses. For this reason, it is recommended that most people take their prescribed daily iron supplement in two or three equally spaced doses. For adults who are not pregnant, the CDC recommends taking 50 mg to 60 mg of oral elemental iron (the approximate amount of elemental iron in one 300 mg tablet of ferrous sulfate) twice daily for three months for the therapeutic treatment of iron deficiency anemia . However, physicians evaluate each person individually, and prescribe according to individual needs. Therapeutic doses of iron supplements, which are prescribed for iron deficiency anemia, may cause:

  • gastrointestinal side effects such as nausea,
  • vomiting, constipation, diarrhea,
  • dark colored stools, and/or abdominal distress

Starting with half the recommended dose and gradually increasing to the full dose will help minimize these side effects. Taking the supplement in divided doses and with food also may help limit these symptoms. Iron from enteric coated or delayed-release preparations may have fewer side effects, but is not as well absorbed and not usually recommended.Physicians monitor the effectiveness of iron supplements by measuring laboratory indices, including reticulocyte count (levels of newly formed red blood cells), hemoglobin levels, and ferritin levels. In the presence of anemia, reticulocyte counts will begin to rise after a few days of supplementation. Hemoglobin usually increases within 2 to 3 weeks of starting iron supplementation. In rare situations parenteral iron (provided by injection or I.V.) is required. Doctors will carefully manage the administration of parenteral iron . [/html]

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