Iron
By Jennifer Sofia Catalano
What is Iron?
Iron is the second most abundant metal on earth and its use is traced back to the last 5000 years. In human physiology, this mineral is needed to transport oxygen from the lungs to the rest of our body and carbon dioxide back to the lungs, but also for storing and releasing oxygen in muscle cells. This is done via the haemoglobin in the red blood cells which travel round our organs.
Beef is rich in iron, amongst other nutients
How is it acquired, stored and excreted?
Iron is mostly present in haemoglobin, in red blood cells and therefore any loss of blood (e.g. menstruating women) means a loss of this mineral which needs to be replaced. It iis so vital to the body, that it is not excreted as such but is lost through sweating, dead skin cells and also from the mucus in the lining of the intestine. This nutriant is replaced through our diet and it is our intestine (in particular our duodenum) which regulates how much we need to absorb from what we eat. Factors which influence how much our body absorbs revolve around how much is already stored in our system, how much haemoglobin and oxygen there is in the blood and how many new red blood cells are being made. It is stored primarily in the liver cells but also the bone marrow and spleen.
How Much Iron Should We Take?
Recommended Dietary Allowances for Iron for Infants,Children, and Adults taken from the Office of Dietary Supplements.| Age | Males
(mg/day) | Females
(mg/day) | Pregnancy
(mg/day) |
|---|
| 7 to 12 months | 11 | 11 | N/A | | 1 to 3 years | 7 | 7 | N/A | | 4 to 8 years | 10 | 10 | N/A | | 9 to 13 years | 8 | 8 | N/A | | 14 to 18 years | 11 | 15 | 27 | | 19 to 50 years | 8 | 18 | 27 | | 51+ years | 8 | 8 | N/A |
Who n is most at risk of deficiency?
Growth in human bodies requires even more iron than usual. Therefore pregnant women and children require more than other groups. Women who menstruate, people who have lost blood or blood donors need to compensate for iron lost. People who suffer from gastro-intestinal diseases need to compensate for any intestinal blood loss and/or poor absorption.Adult men and postmenopausal women are therefore least likely to be deficient in this mineral, and furthermore are discouraged from taking iron supplements since they are more at risk of having too much of it.
What are the Symptoms of Deficiency?
If we are iron deficient then or bodies begin by consuming the stored iron, and then the iron in the haemoglobin. A blood test for haemoglobin, reveals if the concentration is adequate, and if it is not then iron supplements are administered. Since iron is vital to growth in humans, its deficiency in children, impairs physical and cognitive growth. More generally, since iron carries oxygen to our tissues and muscle, if we lack iron we suffer fatigue and low physical productivity. Interestingly, it has been noted that people who eat dirt or clay (condition known as pica, geophagia) are typically iron deficient, though scientists have not yet confirmed how this link is scientifically explained.
What happens if too much is present in the body?
- Bacterial Infection This is because bacteria feed on iron and reproduce much faster if there is more iron present. People who suffer from haemochromatosis, absorb iron at a greater rate than normal, have higher levels of iron in their system and are more likely to suffer bacterial infections.
- Heart Disease Many studies show that build up of iron (e.g. in postmenopausal women) is linked to heart disease, though there are differing scientific explanations for how this occurs. Since iron stores decrease via blood letting, (phlebotomy) this can help prevent heart disease.
- Organ Damage This occurs in people who are unknowingly absorbing and storing too much iron, (e.g. sufferers of haemochromatosis), and unfortunately are only diagnosed after the damage to the organ has occurred. People receiving excessive transfusions are also at risk.
- Death To reach a level of iron so high as to cause death, is typically because of accidental ingestion of iron supplements and not because of iron in diets.
Which foods contains Iron?
Iron is essential to plants and animals and it is therefore found in eating both, however its form changes between the two, and its absorption is also subject to the presence of other chemicals and minerals in the intestine at the same time. - Haeme Iron is present in red meat, fish and poultry since it comes from haemoglobin in those animals. It is the most easily absorbed.
- Non-haeme iron is present in plants. Examples of iron rich plants would be legumes like lentils and dark green leafy plants like broccoli. In order to render non-haeme iron more easily absorbed it is important to accompany it with foods rich in vitamin C since this facilitates the absorption.
Food Sources of Iron ranked by milligrams of iron per standard amount; also calories in the standard amount. (All are ≥ 10% of RDA for teen and adult females, which is 18 mg/day.) | Food, Standard Amount | Iron (mg) | Calories | | Clams, canned, drained, 3 oz | 23.8 | 126 | | Fortified ready-to-eat cereals (various), ~ 1 oz | 1.8 -21.1 | 54-127 | | Oysters, eastern, wild, cooked, moist heat, 3 oz | 10.2 | 116 | | Organ meats (liver, giblets), various, cooked, 3 oz a | 5.2-9.9 | 134-235 | | Fortified instant cooked cereals (various), 1 packet | 4.9-8.1 | Varies | | Soybeans, mature, cooked, 1 cup | 4.4 | 149 | | Pumpkin and squash seed kernels, roasted, 1 oz | 4.2 | 148 | | White beans, canned, 1 cup | 3.9 | 153 | | Blackstrap molasses, 1 Tbsp | 3.5 | 47 | | Lentils, cooked, 1 cup | 3.3 | 115 | | Spinach, cooked from fresh, 1 cup | 3.2 | 21 | | Beef, chuck, blade roast, lean, cooked, 3 oz | 3.1 | 215 | | Beef, bottom round, lean, 0" fat, all grades, cooked, 3 oz | 2.8 | 182 | | Kidney beans, cooked,1 cup | 2.6 | 112 | | Sardines, canned in oil, drained, 3 oz | 2.5 | 177 | | Beef, rib, lean, º" fat, all grades, 3 oz | 2.4 | 195 | | Chickpeas, cooked, 1 cup | 2.4 | 134 | | Duck, meat only, roasted, 3 oz | 2.3 | 171 | | Lamb, shoulder, arm, lean, º " fat, choice, cooked, 3 oz | 2.3 | 237 | | Prune juice, æ cup | 2.3 | 136 | | Shrimp, canned, 3 oz | 2.3 | 102 | | Cowpeas, cooked, 1 cup | 2.2 | 100 | | Ground beef, 15% fat, cooked, 3 oz | 2.2 | 212 | | Tomato puree, 1 cup | 2.2 | 48 | | Lima beans, cooked,1 cup | 2.2 | 108 | | Soybeans, green, cooked, 1 cup | 2.2 | 127 | | Refried beans, 1 cup | 2.1 | 118 | | Beef, top sirloin, lean, 0" fat, all grades, cooked, 3 oz | 2.0 | 156 | | Tomato paste, º cup | 2.0 | 54 | a High in cholesterol
Sources:
Nutrient values from Agricultural Research Service (ARS) Nutrient Database for Standard Reference, Release 17. Foods are from ARS single nutrient reports, sorted in descending order by nutrient content in terms of common household measures. Food items and weights in the single nutrient reports are adapted from those in the 2002 revision of the USDA Home and Garden Bulletin No. 72, Nutritive Value of Foods. Mixed dishesand multiple preparations of the same food item have been omitted from this table. For foods not listed in this table, please refer to the U.S. Department of Agriculture's Nutrient Database Web site at the following URL : http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl
http://en.wikipedia.org/wiki/Human_iron_metabolism
http://ods.od.nih.gov/factsheets/iron.asp
http://en.wikipedia.or/wiki/Iron_deficiency_(medicine)
http://emedicine.medscape.com/article/166933-overview
http://www.nhlbi.nih.gov/health/dci/Diseases/ida/ida_whoisatrisk.html
http://whqlibdoc.who.int/publications/2008/9789241596657_eng.pdf
To see above pages, please cut and paste the URL into your browser.
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