One of the most studied nutrients in history, iron deficiency and toxicity are well understood and researched. Most of the iron in our bodies is complexed with hemoglobin and is essential for oxygen transport in the blood. Iron deficiency is a major problem in under-developed countries and is the most commonly deficient nutrient in the world. Fortification of various products is wide-spread in the United States and around the world to combat this deficiency.
The absorption of iron takes place in the duodenum and upper jejunum (small intestine). Of total iron intake, only 5-15% is absorbed. Absorption depends on many factors: the body's requirement (during deficiency state absorption will be better); type of iron (ferric or ferrous form); and concurrent intake of some food items or medication (citrus fruit increase absorption whereas medicines such as antacids can reduce absorption).
Diets based on cereals permit only low levels (2-5%) of absorption, while diets containing low levels of cereals and high levels of meat and fish permit 10-20% absorption. Oxalates and phytates in the diet, as well as its protein quantity, affect the absorption also. Presence of vitamin C enhances the iron absorption, which is why consuming citrus fruit along with iron helps. An excess of calcium or intestinal parasites such as hookworm is believed to reduce absorption of iron.
Tips for Getting and Absorbing Iron:
Various salt forms of iron exist, chelated sources of iron are also excellent sources of this mineral when supplementation is necessary.
Unfortunately, too much iron can lead to oxidative stress (forming excessive free radicals) and adhesion of blood cells. The iron load on most males in developed countries is sufficient and in many cases in excess. It is for this reason that many studies do not recommend that men take supplemental iron. Recent studies have also shown that nearly 90% of women (in the United States) within child-bearing ages are not deficient in iron. The current US RDA for iron is 18mg.
Iron supplementation, with as much as 200mg of elemental iron per day, is the obvious therapy for treating and preventing the recurrence of iron deficiency anemia. Note, however, that it is dangerous to take iron supplements without first having ferritin levels tested, as taking iron when it is not called for can cause iron overload disorder, potentially a dangerous condition.
The following observations have been made regarding iron:
'Heme' iron (from meat) is 10 times more absorbable than most other forms of iron.
Iron is routinely prescribed for pregnant women during the second and third trimesters, when blood volume increases by 50% and the growing baby is also making blood. Hemoglobin, the blood component that carries oxygen to the cells, is composed in part of iron. During pregnancy, the baby receives plenty of this critical mineral because the mother's body absorbs iron more efficiently. [Eskeland B, et al. Acta Obstetricia et Gynecologica Scandinavia 1997;76: pp.822-8]
There is some controversy about whether iron supplementation is really needed or effective, except for women such as diabetics or those with anemia, whose iron deficiency is a real threat. [Lao TT, Tami KF. Diabetes Care 1997;20(9): pp.1368-9] Iron supplementation for anemia often fails because women don't take iron long enough, say researchers at the University of California, Berkeley. They suggest beginning iron supplementation before conception and continuing until breastfeeding is finished. [Viteri FE. Nutr Rev 1997;55(6): pp.195-9]
The best way to get iron is from natural foods. Iron supplements may cause nausea and constipation, making the common discomforts of pregnancy worse. Too much iron is also bad for the circulation. If a doctor recommends iron supplements, iron chelate is better tolerated by the body and is available from drugstores. The U.S. RDA is 30mg.
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