Iron

What is it and where does it come from?

Iron is the most abundant element on earth and is an essential trace element for humans. It is found in many different foods, including meat and vegetables, and can also be added to food through the use of cast iron pots and pans. Supplements contain iron in many different forms, of which ferrous succinate and ferrous sulphate are best absorbed by the body, although ferrous sulphate can cause stomach problems. A good alternative is ferrous gluconate and ferrous fumurate. A hydrolyzed protein chelate form called ferritin is also available. In the body, iron is primarily stored in the bone marrow, spleen and liver.

General information

Iron has the atomic number 26 in the periodic table of elements and has the chemical symbol Fe. Together with cobalt and nickel, it is a ferromagnetic metal. It occurs in nature both in its pure form as a metal and in a variety of chemical compounds. In these chemical compounds, iron occurs as bivalent or trivalent iron (Fe2+ or Fe3+). Iron belongs to the trace elements and is the most common of these in the human body. The total iron content in adults is approx. 4,000 to 5,000 mg, i.e. 4-5 g, of which approx. 2,500 mg, i.e. 2.5 g, is found in haemoglobin. The rest is found in the iron depots (approx. 1,000 mg) and in myoglobin. The iron-containing enzymes contain approx. 8 mg. An entire epoch in human history (from around 800 to shortly before the birth of Christ) is named after this element. During this time, man discovered iron as an important raw material for tools and, unfortunately, weapons.

Functions

The most important function of iron is to bind oxygen to the hemoglobin molecule in the red blood cells. In this way, oxygen is transported from the alveoli (air sacs) in the blood to the body's cells. An iron deficiency impairs the formation of hemoglobin, resulting in the most common form of anemia, iron deficiency anemia. One of the consequences of this is a reduced supply of oxygen to the body. As already mentioned, iron is needed to synthesize haem and therefore haemoglobin. Haemoglobin is the red blood pigment in the erythrocytes, the red blood cells. It is made up of approx. 94% globin protein and 6% haem, to which iron is bound. Iron bound to haemoglobin binds oxygen and thus transports it from the lungs to all cells of the organism. On the "return journey", the haemoglobin transports the carbon dioxide from the cells back into the lungs, where it is then excreted with the air we breathe. Carbon dioxide is produced as a combustion product of cellular metabolism. Iron plays another important role in the immune system's fight against pathogens, on the one hand as a component of many enzymes, and on the other hand the pathogens themselves need iron to survive. The availability of iron for bacteria persisting in the cell and their host is in a finely regulated balance. On the one hand, the host cells need iron as a cofactor for fighting pathogens, especially in the production of aggressive oxygen and nitrogen radicals. On the other hand, intracellular pathogens are dependent on iron for their growth and thus on the host's iron reserves. Experiments have shown that both a deficiency and an excess of iron impair the body's scavenger cells (macrophages) in their ability to control bacterial pathogens. The biological availability of iron varies depending on the composition and type of food. Iron in bivalent form is well absorbed by the body, e.g. the ferrohaem contained in meat (consists of protoporphyrin and Fe2+). Vegetable iron (vegetables, salads and fruit), on the other hand, is in trivalent form. It must first be reduced to bivalent iron and is therefore more difficult to absorb in the intestine. This means that significantly larger quantities of iron-rich foods must be consumed if you eat an exclusively vegetarian diet.

Iron is absorbed in three steps:

• Absorption from the intestine into the mucosa cells (mucosal cells)
• Protein-dependent transport and storage in the mucosa cells
• Release of the iron to transport proteins in the blood

The organism is able to adapt the resorption to the respective iron requirement. With an increased iron requirement, the resorption rate can be increased to around 40 percent, whereas with a high iron stock it can be reduced to around 5 percent. On average, around 20 percent of iron is absorbed from animal foods and around 3 to 8 percent from plant foods.

Foods containing iron

Bread, meat (especially pork liver) and sausage products are the most important sources of iron. The degree of utilization is important for iron intake, which is why meat is one of the most important sources. Iron from meat is much better absorbed than iron from plant products, of which only between 2 and 10% of the iron contained can be absorbed and utilized in the human intestine, depending on the plant. Vegetarians and vegans should therefore pay particular attention to their iron intake. Vegans are vegetarians who abstain from all animal products, including eggs and milk. It may be necessary for vegetarians and especially vegans to take additional iron in the form of iron-containing supplements.

In this context, it should also be noted that a purely vegetarian diet for children does not usually provide the necessary amount of iron. An undersupply of this trace element can have far-reaching consequences, especially for children, who have an increased iron requirement for healthy growth and optimal development of their mental abilities.

Foods with a high iron content and substances or conditions that inhibit absorption

• Spinach has a high oxalic acid content, which has an inhibiting effect on absorption.
• Soybeans have a high proportion of resorption-inhibiting phosphate. This is particularly tragic as soybeans are a food with a very high iron content.
• Milk and dairy products inhibit the absorption of iron due to their high calcium content. Resorption-inhibiting substances or conditions
• Certain dietary fibers (e.g. bran)
• calcium
• carbonates
• Oxalates (e.g. spinach, rhubarb, cocoa)
• Phytal
• Protein deficiency in the diet
• phosphate
• Tannins (e.g. tea, coffee)

Iron deficiency

Alongside iodine deficiency, iron deficiency is the most common mineral deficiency in industrialized countries and iron deficiency anaemia is the most common iron deficiency disease worldwide. In general, however, severe iron deficiency is very rare in Europe, but many people, especially women (the figures vary between 20 and 50%), are affected by mild to moderate iron deficiency. It can occur, for example, with a very unbalanced diet (diet, no meat) as well as through the predominant intake of poorly utilizable iron compounds. Iron can also be lost through heavy bleeding, for example during menstruation, through injuries and through frequent blood donations. Diseases in the gastrointestinal tract can impair iron absorption, for example due to inadequate conversion processes. Iron deficiency also occurs in the context of certain diseases (e.g. infections, hormonal disorders, rheumatism, cancer) or can be caused by medication (e.g. antibiotics, some painkillers and anti-inflammatory drugs). A lack of vitamin B6 can contribute to iron deficiency. Symptoms of iron deficiency include lack of physical and mental performance, tiredness, weakness, headaches, sensitivity to the weather, nervousness and irritability. It can lead to paleness, brittle, rough skin and brittle hair, grooves in the fingernails and cracks in the corners of the mouth can form. Palpitations, shortness of breath, burning tongue and constipation can also occur. An iron deficiency also prevents the activity of important enzymes, which in turn are involved in many bodily processes and are therefore impaired. Furthermore, thermoregulation (the body's heat balance) is disturbed, immune deficiencies can occur and susceptibility to infections can increase. There is a warning about the risk of premature birth during pregnancy. This is significantly higher in women who suffer from iron deficiency. The risk of stillbirth also increases.

Safety and side effects

Iron is probably safe and harmless for most people when taken orally in appropriate amounts. However, it can cause side effects including stomach upset, stomach pain, constipation, diarrhea, nausea and vomiting. Taking iron supplements with food appears to reduce these side effects. However, food can also reduce iron absorption. For this reason, iron should be taken on an empty stomach if possible. If it causes too many side effects, it can be taken with food. You should try not to take iron in combination with foods containing dairy products, coffee, tea or cereals. There are many forms of iron products such as ferrous sulphate, ferrous gluconate, ferrous fumarate and others. Some iron products, such as products containing a polysaccharide iron complex, are claimed to cause fewer side effects than other iron products. However, there is no scientific evidence to support these claims. Some enteric-coated iron products or delayed-release iron products may cause nausea in some people. These products are also less well absorbed by the body. Liquid iron supplements may stain teeth black. There are concerns that high iron intake may increase the risk of heart disease. Some studies show that people who consume a lot of iron - especially in the form of food sources such as red meat - are more likely to develop heart disease. This could particularly be the case for people who suffer from type 2 diabetes. However, these observations are controversial. Other studies do not show that iron increases the risk of heart disease. It is too early to make a conclusive statement about whether iron increases the risk of heart disease.

The maximum tolerated amount of iron - the highest intake at which no undesirable side effects are to be expected - is as follows:

• Children and infants under 14 years: 40 mg/day
• People aged 14 and over (including pregnant and breastfeeding women): 45 mg/day

These amounts do not apply to people undergoing medical treatment for iron deficiency.

Overdose and poisoning

A side effect of increased iron intake may be a darkening of the stool, which has no medical significance. Other symptoms include weakness, blue coloration of lips, hands and nails, digestive problems, diarrhea, constipation and even coma. An overdose rarely occurs, too much iron is excreted in healthy people. Nevertheless, accidental ingestion of large quantities of iron-containing medicines or preparations can lead to iron poisoning. This is rare in adults, but in children these accidents, which can have a fatal outcome, are more frequent. The lethal dose is approx. 35-630 mg/kg body weight (commercially available iron tablets each contain approx. 40 to 100 mg iron). In infants with a body weight of 10 kilograms, 5 iron tablets can be fatal. The symptoms of acute iron poisoning occur about 30 to 120 minutes after ingestion and consist of severe vomiting, severe stomach pain and diarrhea. The high loss of fluids can lead to a shock situation which can result in death. Once patients have recovered from the initial symptoms, a severe drop in blood pressure, convulsions and severe liver inflammation can occur about a day later. In the event of an overdose of iron, drinking milk is recommended, which can lead to the formation of iron-protein complexes, i.e. the binding of iron to proteins contained in milk.

Precautions and warnings

Pregnancy and breastfeeding: Iron is probably safe and harmless for pregnant and breastfeeding women who have enough iron stored in their bodies when used below the maximum tolerated amount of 45 mg of elemental iron per day. Higher amounts are probably not safe if taken orally. If you do not suffer from an iron deficiency, you should not take more than 45 mg of elemental iron per day. Higher doses regularly cause gastrointestinal side effects such as nausea and vomiting. High hemoglobin levels at the time of birth are associated with problems during childbirth. Hemoglobin is the molecule in red blood cells that contains iron.

Diabetes: There are concerns that a diet rich in iron may increase the risk of heart disease in women with type 2 diabetes, although this has not yet been proven. If you have diabetes, you should talk to your doctor about your iron intake.

Stomach and intestinal ulcers: Iron can cause irritation and aggravate these conditions.

Inflammatory bowel diseases such as ulcerative colitis or Crohn's disease: iron can cause irritation and aggravate these conditions.

Hemoglobin disorders such as thalassemia: Taking iron could result in too much iron in the body in people suffering from these disorders. For this reason, people suffering from these conditions should not take iron supplements unless prescribed by a doctor.

Premature babies: Giving iron to premature babies with low vitamin E blood levels can cause serious problems. The vitamin E deficiency should be corrected before iron is administered. For this reason, the administration of iron to premature babies should be discussed with a doctor.

Interactions

Care should be taken when combining iron with the following medications

Antibiotics (quinolone antibiotics)

Iron could reduce the amount of antibiotics absorbed by the body. Taking iron in combination with quinolone antibiotics could reduce the effectiveness of these antibiotics. To avoid this interaction, iron should be taken two hours before or two hours after antibiotics.

Antibiotics (tetracyline antibiotics)

Iron can bind to tetracyline antibiotics in the stomach and reduce the amount of tetracyline antibiotics that the body can absorb. Taking iron in combination with tetracyline antibiotics could reduce the effectiveness of tetracyline antibiotics. To avoid this interaction, iron should be taken two hours before or four hours after taking tetracyline antibiotics.

Bisphosphonates

Iron can reduce the amount of bisphosphonates absorbed by the body. Taking iron in combination with bisphosphonates can reduce the effectiveness of bisphosphonates. To avoid this interaction, bisphosphonates should be taken at least 2 hours before iron or later in the day.

Levothyroxine

Levothyroxine is used for hypothyroidism. Iron can reduce the amount of levothyroxine absorbed by the body. Taking iron in combination with levothyroxine could reduce the effect of levothyroxine.

Penicillamine

Penicillamine is used for Wilson's disease and rheumatoid arthritis. Iron can reduce the amount of penicillamine absorbed by the body. Taking iron in combination with penicillamine could reduce the effect of penicillamine. To avoid this interaction, iron should be taken two hours before or two hours after penicillamine.

Chloramphenicol

Iron is important for the production of red blood cells. Chloramphenicol could reduce the formation of new red blood cells. Long-term use of chloramphenicol may reduce the effects of iron on red blood cell formation. However, as most people only take chloramphenicol for a short period of time, this is not a major problem.

Prophylaxis

There are a number of reasons why the daily iron requirement may not be met or may result in an increased iron requirement. These are mainly pregnant and breastfeeding women, or people who do not absorb enough iron due to their dietary habits. In order to prevent possible illnesses caused by iron deficiency, it is necessary in these cases to take additional iron supplements. However, these supplements should only be taken for a limited period of time, as a healthy person does not need a permanent supply of iron in the form of medication once their iron stores have been replenished. People suffering from chronic iron deficiency without malnutrition should be examined for chronic blood loss in the gastrointestinal tract.

Requirements

The German Nutrition Society recommends 10 to 12 mg of iron as part of a healthy diet for people from the age of 8. From the onset of menstruation until the menopause, women should consume slightly more, namely 15 mg of iron, due to monthly blood loss. Pregnant and breastfeeding women have a particularly high iron requirement. Their requirement is around 30 mg for pregnant women and 20 mg for breastfeeding women. Gynaecologists usually recommend taking iron supplements because this requirement cannot always be covered by food. An increased need for iron can occur in growing children, the elderly, athletes, vegetarians, frequent blood donors and in a number of diseases (e.g. blood diseases, rheumatism and tumors). Vitamin C, some amino acids and fructose, for example, improve the absorption of iron. Iron is therefore often contained in iron supplements in combination with vitamin C. Other substances such as tannins from coffee or tea and oxalic acid from spinach, on the other hand, inhibit the absorption of iron from food.

Requirements in sport

As the unhindered transport of oxygen within the body and the function of iron-containing enzyme systems in energy metabolism are important prerequisites for peak physical performance, iron is an important trace element for athletes. An insufficient supply leads to a noticeable drop in performance. The normal iron requirement is 1.5 to 2 mg per day. However, the athlete's iron requirement is up to twice as high as normal. My recommendation is to take a dose of 30 to 40 mg a day, if possible through food. Only take supplements if prescribed by a doctor.

References

1. Diebschlag W (1985) The optimal diet for athletes. Competitive Sports 1/85
2. Findlay S, Podolsky D, SilbernerJ (1992) Iron And Your Heart. U.S. News & World Report 21.09.1992