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Mineral Nutrient :: Iron


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Content Below: What is Iron · Benefits · Deficiency Signs · Foods · Supplements · RDA · Toxicity

What is Iron ?
Iron is the trace mineral present in the largest amount in our blood.  It is vital to health and needed by every cell.  It is required in small quantities; from about 2 grams in the adult female, up to 6 grams in the adult male.

Almost two-thirds of the body's iron is found in the hemoglobin in red blood cells.  Another 15 percent is stored by the body in various places including the liver, to be called on when dietary intake is insufficient.  The rest is found in body tissues and as part of enzymes that help the body function.

There are 2 forms of iron in food: heme and non-heme iron.  Heme iron comes from meat and fish; non-heme iron is from plant and dairy sources. The body maintains normal iron status by controlling the amount absorbed from foods that contain iron.

How Iron Benefits Health
Iron has several key roles in the body: oxygen supply, energy production, and to keep the immune system healthy.

Its major role is to deliver oxygen to tissues and muscles throughout the body.  Iron forms the core of hemogloblin, the oxygen-carrying component of red blood cells that enables blood to pick up oxygen from the lungs and carry it to every cell in the body.

Iron is also a core component of another oxygen-carrying protein called myoglobin.  Myoglobin carries oxygen to muscles, especially to the heart and to skeletal muscles.  It helps muscles store oxygen as a reserve for periods of high metabolic activity, such as intense physical exercise.

Cells need oxygen to convert food to the energy that powers every part and function of the body.  If iron is short, less haemoglobin is produced, leading to less oxygen supplied, and less energy generated.  Iron-deficient people tire easily.

Iron benefits energy production in another way too.  Many of the enzymes essential for energy metabolism require iron.

The health of the body's immune system is also dependent on adequate iron, which builds resistance to stress and disease.

The many ways that iron benefits the body are summarized here.

:: Iron Benefits & Functions
1. most important for production of the haemoglobin that is necessary for the formation and oxygen-carrying ability of red blood cells, and hence the delivery of oxygen to all parts of the body
2. needed for formation of myoglobin that carries oxygen to, and helps stores oxygen in muscle tissue
3. its role in supply of oxygen to cells and muscles makes iron essential for energy production, since oxygen is needed for energy metabolism (conversion of food to energy)
4. component of many enzymes (catalysts that drive cellular functions) needed for biochemical processes in the body, including energy release
5. essential cofactor in the production of neurotransmitters like norepinephrine, serotonin, and dopamine
6. required for proper functioning of the immune system, and resistance to disease and infections
7. iron in the form of ferrous sulfate is the standard treatment for iron deficiency anemia, including that due to menorrhagia (excessive menstrual bleeding)
8. iron supplementation (under the guidance of a healthcare professional) can help prevent anemia in pregnant women; anemia during pregnancy is linked to consequences such as pre-term birth, low birth weight, and maternal mortality
9. critical for regulation of cell formation and growth, especially in children
10. iron supplementation appears to improve cognitive function in children and adolescents who were previously iron-deficient
11. some studies suggest that iron benefits and helps address symptoms of ADD (attention deficit disorder)


Iron Deficiency Symptoms and Causes
Approximately 1 mg of iron is lost from the body each day through the loss of skin and intestinal cells, and up to 2 mg in women of child-bearing age who lose blood monthly.

Healthy adults absorb around 10% of the normal 10 - 20 mg of iron in food each day, which balances the 1 to 2 mg that the body loses.  For this reason, most health bodies set the recommended daily allowances (RDA) for it at around 10 times what the body needs.

However, for a variety of reasons that include insufficient intake of foods that contain iron, poor absorption, medical conditions that cause internal bleeding, and excessive menstruation, a significant proportion of people have iron deficiency symptoms.

This is despite the fact that the body conserves iron by re-using iron from old blood cells to make hemoglobin for new blood cells.  Iron deficiency is one of the most common nutritional deficiencies around the world.  It is estimated that more than a quarter of the world is iron deficient.

Those at risk of low iron levels :
  • people with gastro-intestinal conditions that make it hard to absorb the iron in food
  • those with low stomach acid (hypochlorhydria), as there needs to be sufficient hydrochloric acid in the stomach, for iron to be absorbed
  • hypochlorhydria is common among the elderly, putting them at risk
  • similarly, antacids should be taken separately from iron rich foods
  • those with chronic herpes infections or candidiasis
  • strict vegetarians: iron from plants is less easily absorbed than iron from meat
  • those who engage in strenuous exercise and who perspire heavily deplete iron from the body
  • people with internal bleeding, such as in the intestines from an ulcer
  • people who donate blood frequently
  • women of child-bearing age, especially if they have heavy periods
  • women who are pregnant or who are breastfeeding
  • babies and toddlers fed exclusively on formula milk that lacks iron
  • adolescents undergoing rapid growth who do not eat enough iron rich foods

To balance, the body does increase absorption of iron from food at times of need, such as in children during periods of rapid growth, and in women during pregnancy and lactation.

Certain food compounds hinder iron absorption: phytic acid (found in whole grains and legumes), oxalates (in chocolate and spinach), phosphates (in carbonated drinks and canned food), and caffeine and tannin (coffee and tea).  However these foods do not affect people with a healthy iron level much, if not consumed in excess.

Large doses of zinc or vitamin E also decrease iron absorption.

The body keeps some stores of iron, but if iron levels continue to be low over a period of time, the stores are depleted.  When that happens, iron deficiency symptoms arise.

One of the classic iron deficiency symptoms is iron-deficiency anemia.  It is the most common nutrient deficiency disorder in developed countries, and is characterized by red blood cells that tend to be microcytic (smaller than usual) or hypochromic (paler than usual due to less hemoglobin).  It can be aggravated by the fact that low iron levels build high lead levels, and lead interferes with haemoglobin production.  Such cases may benefit from iron supplements or more iron rich foods.

Note: even when iron level is high, anemia can still happen if iron utilization is impaired, such as in patients with cancer or rheumatoid arthritis.

But even before anaemia develops, mild deficiency can already give rise to a number of iron deficiency symptoms.

:: Iron Deficiency Symptoms
1. iron-deficiency anemia, which limits oxygen delivery to cells; symptoms may include headaches, dizziness, irritability, pale skin, cold hands and feet, whites of eyes appearing bluish, lack of energy, extreme fatigue, rapid heartbeat, low immune function with increased susceptibility to infection, brittle nails, shortness of breath, sore or inflamed tongue or mouth, lack of appetite, blood in stools, restless legs syndrome
2. food cravings for inedible items such as ice, paint, starch, clay, or dirt (a condition called Pica)
3. increased intestinal inflammation or irritation
4. depression or apathy
5. insomnia or disturbed sleep
6. decrease in ability to concentrate
7. impaired mental skills that can affect memory and job performance
8. learning disabilities, short attention spans, and lower IQ in children may be associated with iron deficiency
9. irregular menstrual periods
10. brittle hair
11. hair loss
12. nails that are spoon-shaped or that have ridges running lengthwise
13. insufficient iron may increase the risk of lead poisoning in children


Iron Foods
Iron from meat (heme iron) is more easily absorbed than iron from plants or dairy products (non-heme iron).  However, eating meat or fish or poultry with dark green leafy vegetables or beans at the same time, can improve the absorption of non-heme iron significantly.

Foods containing vitamin C or organic acids like citric or lactic or malic acid have also been found to increase iron absorption.

Iron in grains is mainly found in the germ and bran.  Milling, which removes the germ and bran, therefore causes about 3/4 of the iron to be lost.  As a result, iron is often added to the refined grain, but added iron in food is not as easily absorbed.

Iron-rich foods are · animal liver · blackstrap molasses · beef · eggs (especially the yolk) · shiitake mushrooms · dark green leafy vegetables like spinach, mustard greens, romaine lettuce, swiss chard, turnip greens · green beans such as winged beans, string beans · dried beans like kidney beans, lentils · soybeans and soy products, especially tofu · rice bran and wheat bran.

Other foods that contain iron include · beans like garbanzo beans (chickpeas), navy beans, lima beans, pinto beans · basil, dill, parsley, rosemary, thyme · black pepper, cinnamon, coriander, cumin, turmeric · brewer's yeast · avocados, bananas, peaches, pears · apricots, dates, figs, prunes, raisins · almonds and brazil nuts · mustard seeds, pumpkin seeds, sesame seeds · lean red meat (lamb, pork, turkey, venison, dark red meat of poultry) · fish (like halibut, salmon and tuna) · shellfish like clams, oysters, crab, shrimp · sea vegetables like spirulina, kelp, dulse (a red seaweed), agar · pumpkins, summer squash · beets, carrots, sweet potatoes, tomatoes, green peas · green leafy vegetables like broccoli, collards, dandelion greens, kale, leek, asparagus, Brussel sprouts · whole grains (such as brown rice, millet, oats, quinoa, wheat).


Iron Supplements
Taking vitamins and minerals in their correct balance is vital to the proper functioning of all vitamins.  They work synergistically, which means that the effectiveness of any one nutrient requires, or is enhanced, sometimes dramatically, by the presence of certain other nutrients.

For this reason, if you are looking to take supplements for maintenance of optimal health, the recommended approach is to take a multi-vitamin that has the proper balance of all the necessary nutrients your body needs.

For a list of reputable top ranked vitamin and mineral supplements chosen in an independent supplement review, see Best Multivitamin Supplements. Many of these are manufactured to pharmaceutical or nutraceutical GMP compliance, which is the highest multivitamin standard possible.

Keep in mind, however, that while mineral supplements are useful to plug nutritional gaps that are almost inevitable in modern diets, and to ensure we get optimal doses of nutrients, they are no substitute for a good diet. Instead, use them to complement a healthy diet and lifestyle.


Iron RDA (Recommended Dietary Allowance)
The Food & Nutrition Board of the Institute of Medicine, National Academy of Sciences, in their 1997-2001 collaboration between the US and Canada, set the daily Adequate Intake (AI) of Iron as follows.

Life Stage | Gender Iron Dosage | Day
Infants 0-6 mths 0.27* mg
Infants 7-12 mths 11 mg
Children 1-3 yrs 7 mg
Children 4-8 yrs 10 mg
Girls 9-13 Yrs 8 mg
Boys 9-13 Yrs 8 mg
Females 14-18 Yrs 15 mg
Males 14-18 Yrs 11 mg
Females 19-50 Yrs 18 mg
Males 19-50 Yrs 8 mg
Females older than 50 Yrs 8 mg
Males older than 50 Yrs 8 mg
Pregnant Women 14-18 Yrs 27 mg
Pregnant Women 19-50 Yrs 27 mg
Lactating Mothers 14-18 Yrs 10 mg
Lactating Mothers 19-50 Yrs 9 mg

These dosages are the minimum required per day to ward off deficiency. In therapeutic use of this nutrient, dosage is increased as necessary for the ailment, keeping in mind Iron toxicity levels.


1 µg = 1 mcg = 1 microgram = 1/1,000,000 of a gram
1 mg = 1 milligram = 1/1,000 of a gram

* Indicates AI figures based on Dietary Reference Intake (DRI) figures


Iron Overdose Symptoms, Toxicity Level & Side Effects
The body has no mechanism to excrete iron.  Instead, extra iron is stored in the body and can easily accumulate to toxic levels.

Symptoms of iron overdose include :
  • anorexia or loss of appetite
  • dizziness
  • nausea and vomiting
  • diarrhea
  • rheumatoid arthritis or pain in the joints
  • damage or bleeding of the stomach or intestinal lining
  • sharp blood pressure drop
  • shock
  • shortness of breath (dyspnea)
  • weight loss
  • liver damage
  • reduced resistance to infection
  • extreme fatigue
  • greyish or bronze hue to the skin

Iron poisoning occurs mainly from excess iron supplementation.  It can lead to metabolic or cardiovascular toxicity and death.  For instance, doses of 3 grams upwards can be fatal to young children.

People with disorders who need frequent blood transfusions are also at risk of iron overdose and should not take extra iron unless directed to do so by their doctor.

Haemochromatosis is a rare hereditary disorder that causes more iron than the normal 10% to be absorbed from foods that contain iron.  This leads to too much it, which can damage organs such as the liver, pancreas, lungs, brain, and heart, and cause diseases like diabetes, heart disorders, liver cirrhosis, and cancer.

Hemochromatosis can be diagnosed through blood tests, and managed if detected.  Treatment typically includes regular phlebotomy (blood removal, akin to blood donation) and avoiding iron-rich foods.

As iron in the body is largely conserved, the body does not need to absorb much iron daily.  The Food and Nutrition Board of the Institute of Medicine set the Tolerable Upper Intake Level (ULs) per day for iron, as follows :

Tolerable Upper Intake Levels (UL) for Iron per Day
Age Male Female Pregnancy Lactation
0 to 13 years 40 mg 40 mg    
14 years & above 45 mg 45 mg 45 mg 45 mg

The ULs do not apply to the therapeutic use of iron for treatment, which should be under the supervision of a healthcare professional.

Cooking with iron pots and pans can add iron to food, which might lead to iron overdose in the long term.

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1. Institute of Medicine, Food and Nutrition Board. Dietary reference intakes for vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. Washington, DC: National Academy Press; 2001.

2. U.S. National Libary of Medicine [NLM] & National Institutes of Health [NIH]: MedlinePlus. NLM-NIH home page. <http://www.nlm.nih.gov/medlineplus>. Use the built-in search function to find specific data. Accessed 2009 March – June.

3. National Institutes of Health, NIH Clinical Center: Office of Dietary Supplements [ODS]. ODS home page. <http://ods.od.nih.gov>. Use the built-in search function to find specific data. Accessed 2009 Mar – Jun.

4. The George Mateljan Foundation: The world's healthiest foods [WHFoods]. WHFoods home page. <http://www.whfoods.com>. Accessed 2009 March – June.

5. Mayo Foundation for Medical Education and Research. Mayo Clinic book of alternative medicine: The new approach to using the best of natural therapies and conventional medicine. New York, NY: Time Inc; 2007. p 67-75.

6. Balch JF, Balch PA. Prescription for nutritional healing: A practical A-Z reference to drug-free remedies using vitamins, minerals, herbs & food supplements. Garden City Park, New York: Avery Publishing; 1990.

7. Ulene A. Dr. Art Ulene's complete guide to vitamins, minerals and herbs. New York, NY: Avery Publishing; 2000.

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