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Iron (Fe)

Iron is one of most important trace elements because of its role in the hemoglobin of the red blood cells that deliver oxygen to all cells and tissues in the body. Around two thirds of the body's total iron supply is found in the red blood cells and in muscle tissue. Around a third of our iron is stored in the liver, spleen, and bone marrow where the red blood cells are produced. A very small amount is used in vital enzymes in the brain, among other places. The organism has a limited ability to excrete iron through the intestinal system, the bile, the urine, and the skin. Moreover, iron is excreted through menstrual blood and breastmilk. An adult contains around 3-6 grams of iron. One litre of blood contains around 500 mg of iron. It is iron that gives blood its red colour, and the oxygenated blood in our arteries is lighter than the deoxygenated blood in our veins.

Functions and importance for

  • Energy turnover and vitality
  • Formation of red blood cells
  • Transportation of oxygen to all parts of the body
  • Co-factor of various enzymatic processes
  • Cell division in the body
  • Growth and learning
  • Immune defence and white blood cells (neutrophil granulocytes)
  • A healthy colour
  • Skin, hair, and nails

Deficiencies and poor utilisation may be caused by

  • Menstrual bleeding - especially excessive or prolonged bleeding
  • Bleeding and blood donation
  • Pregnancy
  • Hard labour and endurance sports
  • Too little gastric juice
  • High intake of bicarbonate (e.g. soda) that reduces gastric juice
  • Insufficient diet (especially vegetarian and vegan diets)
  • Large consumption of coffee and tea, as tannic acid binds iron
  • Oxalic acid (found in e.g. acidic leaves, tea, spinach, cocoa, rhubarb)
  • Too much dietary fibre
  • Large consumption of dairy products (because of calcium)
  • Calcium supplements and manganese supplements
  • Long-term consumption of the following medical drugs:

Antacids that contain calcium, magnesium, and aluminum

Aspirin and other products with acetylsalicylic acid

Tetracycline (antibiotic against acne and infections)

Anti-inflammatory drugs (NSAID)

Disulfiram against alcoholism

Etidronate against osteoporosis

Please note: Iron supplements, calcium supplements, and the above listed medical drugs should normally be taken with 3-4 hour intervals. Bicarbonate supplements should be taken separately from meals.

Deficiency symptoms

  • Fatigue, inner turmoil, and difficulty with concentrating
  • Headache and possibly tinnitus
  • Paleness and lack of vitality
  • Dizziness, breathlessness, and heart palpitations
  • Very dry skin and sporadic change in pigmentation
  • Impaired resistance and dry mucous membranes
  • Cracks at the corners of the mouth and other body orifices
  • Irregularities in hair and nail growth
  • Anemia - typically occurs after prolonged iron deficiency when the body's iron supply is used.
  • Organ failure and death after prolonged chronic iron deficiency where the body's supplies are emptied
  • In children: Impaired growth and learning difficulty


Mainly liver, meat, pumpkin seeds, seeds, beans, stinging nettle, spinach, apricots, whole-grain, red beets, and eggs. Other sources are fish, fruit and vegetables.

Iron content in mg per 100 grams

Linseeds and pumpkin seeds 14-15
Stinging nettle 10
Beef liver 6
Almonds, spinach 5
Lean pork, mackerel 0.7

Recommended daily allowance (RDA)

Varies according to sex, age, and menstrual periods
Children: 1-10 years of age: 8 mg
Adults: 11 years of age and older: 9 mg
Women, menstruating: 15 mg
Women, non-menstruating: 9 mg
Pregnant women: Experts often recommend 40-50 mg from the 10th week of pregnancy, preferably in supplements that also contain folic acid and other nutrients that are relevant for ensuring a healthy pregnancy.

Increased need

  • Menstruation - especially if excessive or prolonged
  • Blood loss or ulcer, injuries, blood donation etc.
  • Small children and growing children
  • Pregnancy
  • Vegetarians and vegans
  • Older people with unbalanced diets
  • Physically hard labour or endurance sports
  • Lacking ability to absorb iron
  • The mentioned deficiency symptoms if iron deficiency is the cause

Absorption and iron types in supplements (oral use)

Iron from animal sources (heme iron) is absorbed more readily than iron from vegetable sources (non-heme iron). The optimal uptake also requires sufficient amounts of gastric juice.

Heme iron tablets as pure supplements would be far too large to swallow. For that reason, many iron supplements contain 10% heme iron and 90% non-heme iron.

Non-heme iron comes in various forms. It is only ferrous iron in the form of ferrous sulfate, ferrous fumarate, or ferrous gluconate that is suited for absorption in the intestines. The absorption of these iron types is almost the same but ferrous fumarate is particularly dependent on gastric juice.

Ferrous bisglycinate is an iron compound (iron chelate) where iron is attached to an amino acid. The uptake of this form is better than non-heme iron (ferrous sulfate, ferrous fumarate, ferrous gluconate) and a lower dosage can be used.

Calcium and certain foods and medical drugs inhibit the body's iron uptake. These are listed in the section "Deficiencies and poor utilisation may be caused by"

Iron status and measurement

Serum ferritin is a biological marker of the body's iron status that is assessed by means of a blood test. Normal iron status is when the iron reserves are in the range of 500-2000 mg and high iron status is when the reserves are in excess of 2000 mg.

If the body's iron reserves are more or less depleted it takes time to replenish them. The body is only able to metabolise around 100 mg of iron per day without the risk of an iron poisoning which is why it takes around 3-6 months to treat an iron deficiency.

Important information

It is possible to be iron deficient without being anemic.
A large percentage of women suffer from iron deficiency, mainly because of menstrual bleeding.

About a fifth of pregnant women develop an iron deficiency.

Also be aware of iron deficiency in children, as this may harm their growth and development.

A low blood percentage may be caused either by an iron deficiency or lack of folic acid, vitamin B12, vitamin B2 or vitamin A, all of which are important for the formation of hemoglobin.

Overdosing - side effects

The symptoms are primarily related to consumption of iron supplements (inorganic supplements in particular) and larger quantities of iron in the gastro-intestinal tract.

  • Nausea and vomiting
  • Abdominal pain
  • Diarrhea or constipation
  • Black or green faeces

Larger doses (over 200 mg per kilogram of body weight) may be lethal. This type of poisoning is mainly observed in children who come in possession of adult iron supplements and take them by mistake. See the following section.

Be careful with excessive iron intake and supplements

Iron is a free radical catalyst in the body. For that reason, iron should only be consumed in adequate amounts and together with neutralising antioxidants

It is believed that a high intake of iron (mainly through meat and supplements) may increase the risk of atherosclerosis, blood clots, and cancer. For that reason people who are not iron deficient should refrain from taking supplements that contain iron in levels higher than those found in normal multivitamins.

As a general rule, specific iron supplements should only be taken in the case of an iron deficiency that has been detected by means of a blood test that measures levels of serum ferritin. Inorganic iron supplements are not recommended, as they have poor bio-availability and increase the risk of side effects. Also, it is worth noting that some multivitamins contain iron while others do not.

In the case of chronic inflammation there is a risk that iron accumulates and exacerbates the condition by causing even more free radicals. Unless an iron deficiency has been detected supplements should also be avoided in the case of autoimmune diseases such as sclerosis.

Iron may inhibit the effect of the following medical drugs:

  • ACE inhibitors against hypertension and certain types of heart failure
  • Penicillamine against kidney stones
  • Drugs against Parkinson's disease
  • Thyroid hormones (Levothyroxin)

Please note: Iron supplements and the mentioned medical drugs should normally be taken with 3-4 hour intervals.