How much iron should you eat per day?

The hemoglobin molecule consists of four subunits (colored in different colors in the figure). Each of the subunits has an iron-containing group – heme (highlighted in red). Air composition in the respiratory tract (volume percentage).
The amount of iron in basic iron-containing foods
The circulation of oxygen and carbon dioxide in the systemic and pulmonary circulation.
Iron metabolism in the body. As Mephistopheles said, “blood is a special kind of juice.” Of all the body fluids, it is the blood that provides a person with oxygen (O₂), vital for the production of energy of all types, and removes the main toxic product of metabolism – carbon dioxide (CO₂). Transportation of these gases occurs with the direct participation of iron atoms. A healthy person’s body constantly contains 4-5 grams of iron. Approximately 70% of this amount is required to saturate the hemoglobin packed in red blood cells, 5-10% of iron comes from myoglobin, which is involved in the transfer of oxygen and carbon dioxide in the muscles, 20-25% is in reserve, mainly in the liver. About 0,1% of total iron is bound to the protein transferrin in the blood plasma. Our body is completely penetrated by the smallest vessels – capillaries. Many of them are so thin that the red blood cells have to change from a ball to a thin rod in order to squeeze inside. Despite the long and difficult path, some of the red blood cells spend less than 30 seconds traveling through the systemic circulation, from the left ventricle to the right atrium, and during this time they must have time to give oxygen to the tissues. Red blood cells pass through the capillaries of the lungs in just 10 seconds, managing to release the CO captured by them in the tissues of the body₂ and replace it with a new portion of O₂. An erythrocyte could not have acquired such turnover if not for hemoglobin. The globin protein that forms its basis has the shape of a ball consisting of four subunits – polypeptide chains folded into pockets. An iron-containing complex, heme, is “embedded” in each of the pockets. Costs one O molecule₂ penetrate into the pocket and connect with iron, as the remaining globin chains begin to turn out sequentially in such a way that the second, third and fourth iron atoms “stick out” out. Here, iron instantly binds with oxygen, which is almost as much in the lungs as in the surrounding air, that is, relatively much. Thanks to the rearrangement of the globin molecule, a so-called cooperative effect occurs: the binding of the first globin subunit to oxygen increases the affinity of the other subunit for it, the binding of the second increases the affinity of the third, and so on. With each step joining O₂ to iron hemoglobin is facilitated. The fourth iron atom thus acquires 500 times greater affinity for oxygen than the first. This mechanism was established by British biochemist and Nobel Prize winner Max Perutz in the 60s of the last century. So, hemoglobin is saturated with oxygen without entering into a strong chemical bond with it, and is 100% converted into oxyhemoglobin of a bright scarlet color, which is typical for arterial blood. In capillaries, where the concentration of O₂ lower than in the arteries, the stability of oxyhemoglobin decreases. Danish physiologist Christian Bohr, father of the famous Niels Bohr, found that not only a higher concentration of carbon dioxide displaces oxygen from hemoglobin, but also the binding of each CO molecule₂ with an iron atom reduces the affinity of neighboring atoms for O₂, that is, there is a struggle between two cooperative systems. As a result, hemoglobin very quickly gives all the oxygen to the tissues and is saturated with carbon dioxide, changing its color to a darker one – the color of venous blood. Hemoglobin is synthesized in the same place where young red blood cells are born – in the bone marrow. There are 400 million hemoglobin molecules in one red blood cell, and every second the bone marrow gives birth to 2,5 million red blood cells! Nevertheless, 70% of the body’s total iron, that is, approximately 3 grams, is enough to saturate the blood with hemoglobin at the rate of 160 g/l. The life of a red blood cell is short – only 125 days. In the “graveyard” of red blood cells, in the spleen, hemoglobin disintegrates and needs to be built anew. What about iron? If it were irretrievably lost, then the body would only have to renew all iron reserves in the blood every 125 days to build new red blood cells. About 25 mg would be required every day, and given that iron is not completely absorbed, even more. Fortunately, iron from destroyed red blood cells largely returns to the site of synthesis, and therefore the daily requirement of a healthy person for iron does not exceed 15 mg. This amount is entirely covered by food. A healthy person does not need to “ironize” food, just as we add salt to it. Despite such favorable conditions, sometimes iron is still not enough. Iron deficiency anemia develops, or in medical terms – iron deficiency anemia, which accounts for 80% of all anemias. This disease has been studied for a long time. From the 6th to the 16th centuries, that is, almost the entire Middle Ages, anemia was considered especially characteristic of young girls and was called “pale illness.” With the development of medicinal chemistry, its cause was identified – a lack of iron in the blood, and the disease was called “chlorosis”, from the Greek word meaning pale green color. Both names well emphasize an outwardly noticeable symptom of the disease. Currently, the disease is called iron deficiency or hypochromic anemia. Not the most important, but the simplest cause of this disease is a lack of iron in food. This happens, for example, with a vegetarian diet (intentional or forced), since of the total amount of iron contained in meat, 20% is absorbed, in fish – 10%, and in plant products – no more than 2-6%. There is practically no iron in milk and cottage cheese. For some reason, everyone puts apples in first place in terms of iron content. Apparently, because the flesh of a cut apple in the air, oxidizing, turns brown, acquiring the color of rust. The merits of apples should not be diminished, but they cannot claim first place, especially since the iron content in them depends on the variety. More significant sources of iron are beef liver and beef, legumes, buckwheat, and rye bread. Successful absorption of iron requires ascorbic acid and B vitamins – B3, B6, B12, Bc (folic acid). A lack of protein in the diet, as well as excess fat and milk, reduces the absorption of iron. Among the internal (endogenous) causes of iron deficiency anemia, one should mention such a completely common condition as increased growth. In full-term infants it occurs at the age of two to three months, and in premature infants even earlier. Infantile anemia at four to six months of age is associated with rapid growth accompanied by depletion of iron stores in the liver and bone marrow. In children in the first year of life, it is aggravated by iron deficiency in mother’s milk and prolonged milk feeding. An increased need for iron appears in young girls due to increased growth, the onset of physiological blood loss, the inhibitory effect of estrogens on iron consumption, and even if they limit themselves in nutrition in order to lose weight. In mature women, anemia can occur during pregnancy and breastfeeding. Another common cause of iron deficiency anemia is illness. Chronic inflammation of the intestines, especially the duodenum, prevents the effective absorption of iron. It is also poorly absorbed when the acidity of gastric juice is low. Slow but steady loss of iron is caused by bleeding ulcers of the stomach and intestines, as well as heavy menstruation (most often associated with diseases of the uterus). Lack of iron leads to a decrease in hemoglobin levels in the blood. And what colors your cheeks with a bright blush? What gives strength to the heart and muscles? What ensures the intense work of thought? Scarlet arterial, oxygenated blood. Iron deficiency anemia is a fairly common disease. Taking into account the asymptomatic forms, more than 30% of the population suffers from it, mainly women of mature age. When iron deficiency occurs, a person does not feel it at first. The symptoms of the disease are not very typical. With anemia, patients are pale, lethargic, and indifferent to everything. Perversion of taste and smell and impaired nail growth are noted. Chronic lack of oxygen supply to internal organs causes dysfunction of the liver, heart muscle, atrophy of the intestinal mucosa, and changes in the electroencephalogram. Atrophy of the esophageal mucosa can lead to difficulty swallowing dry food. These symptoms often occur before the manifestation of overt anemia, during the so-called latent period. Have you perhaps noticed that some people enjoy eating chalk or lime? Actually, this is not entirely normal. But don’t think that the craving for chalk is necessarily caused by a lack of calcium, although this is most often the case. A similar addiction is found in those who suffer from iron deficiency. These same people have a love for the smell of kerosene or car exhaust. Let’s consider a specific example of treatment with iron supplements after blood loss. Let’s say that as a result of injury a person lost a liter of blood, and with it almost a gram of iron. A certain amount of it was replenished from reserves stored in the liver. However, there is still a deficit of approximately 0,5 g. New portions of red blood cells will leave the bone marrow and enter the blood underloaded. Since iron is contained not only in hemoglobin, but also in other proteins, in particular in some enzymes, in fact, to replenish the deficiency and create reserves, approximately twice as much iron is required, for good measure – 1 g. And a gram of iron is approximately one nail! Yes, but how to “drive” it into the bone marrow? There is no use in swallowing iron filings; they pass through the intestines in transit and are not absorbed. It is possible to obtain very fine iron powder by reducing its oxide in a stream of hydrogen. But only 0,8% of the administered amount is absorbed from this powder, that is, in order for the required gram to enter the blood, you need to eat 125 g of powdered iron! An upset stomach is guaranteed. But there will be a disorder, and 1 g will not be absorbed. Therefore, iron is used in the form of salts or complexes, which are better absorbed. Nowadays lactate, sulfate, fumarate, ferric chloride, as well as complexes of iron salts with ascorbic acid, folic acid and other vitamins are used. In recent years, evidence has emerged indicating that when treating hypochromic anemia with iron preparations, it is necessary to prescribe vitamin E (alpha-tocopherol) to increase the effectiveness of therapy and to reduce the pro-oxidant effect inherent in iron ions. The intake of iron into the body can be extended over time by taking slow-acting medications. If you need to increase the iron content in the body urgently or if for some reason it is impossible to take it orally, drugs for intravenous administration are used, but this is the concern of doctors. The criterion for the effectiveness of treatment is an increase in hemoglobin by 0,15-0,3 g/l per day. In the first days the effect is higher, but gradually decreases. Since the daily increase may not be noticed, and treatment requires a long time, the tests are repeated no more than once every two weeks. An increase in hemoglobin content over this period by 2% is considered satisfactory. Unfortunately, there are forms of the disease in which iron, introduced into the stomach and then released into the blood, is not absorbed. Such patients are given red blood cell transfusions if necessary. They began to treat chlorosis with iron preparations a very long time ago, in the 1917th century, but the reason for the action of the medicine was not understood. Even the XNUMX edition of a pharmacology textbook notes: “What explains the effect of iron in chlorosis has not yet been clarified with precision. It would seem that there is no need at all for a special supply of iron, since, as far as is known, daily food usually contains iron in excess.” As you can see, medicine has made tremendous strides since then. We have figured out, and only partially, the disease in which there is little iron in the body. But there can be too much of it! The body usually has a relatively constant supply of iron in the form of water-soluble ferritin and insoluble hemosiderin. The first serves as a temporary storage of iron reserves, the second is a form of deposition of excess in tissues. A constant level of iron is maintained by regulating absorption, but not excretion. Iron supplied with food is first deposited in the intestinal mucosa. When needed, it is transported by the transport protein transferrin to the bone marrow and liver. If the iron depot is full and there is enough of it in the blood, then the iron remains in the intestinal cells, which are replaced with new ones every three to four days, and the excess iron is removed along with the desquamated epithelium. 1-2 mg of iron is excreted from the body per day (if there is no blood loss). There is a hereditary disease – hemochromatosis (pigmentary cirrhosis, bronze diabetes), the cause of which is the loss of the intestines’ ability to regulate the supply of iron as needed. As a result, all iron available from food enters the blood. The disease manifests itself not only in the color of the skin, but also in the massive deposition of iron in the organs, especially in the liver. The famous geneticist I.V. Davydovsky called this disease “degenerative rusting.” Mostly men suffer from hemochromatosis. The first symptoms are pain in the right hypochondrium, an increase in hemoglobin to 130-170 g/l, and a decrease in the number of red blood cells. In the body of some patients, a 100-fold amount of iron manages to accumulate. Hemochromatosis is a serious disease, but not hopeless. There are now drugs that capture iron and convert it into a soluble state, thereby facilitating excretion in the urine. Another disease associated with excess iron in the blood is hemosiderosis. It is quite rare and occurs with massive destruction of red blood cells. Hemosiderosis can be caused by frequent blood transfusions, poisoning (in particular, mushrooms), snake bites, and some infectious diseases, such as malaria. In addition, increased iron content in the body can lead to the activation of pathogenic microbes and weakening of the immune system. In a word, a lack of iron is bad, an excess is also bad. In the human body, everything should be in moderation. Illustration: “Composition of air in the respiratory tract (volume percentage).” Air composition in the respiratory tract (volume percentage). Note. Exhaled air differs from alveolar air because it mixes with residual air remaining in the trachea and bronchi. Illustration: “The circulation of oxygen and carbon dioxide in the systemic and pulmonary circulation.” The circulation of oxygen and carbon dioxide in the systemic and pulmonary circulation. In the pulmonary circulation, carbon dioxide is displaced from hemoglobin and replaced with oxygen. In this case, the blood becomes scarlet in color. Through the systemic circulation, arterial blood, in which each hemoglobin molecule carries four oxygen molecules, enters the tissue capillaries. The tissues contain a lot of carbon dioxide and a moderate amount of oxygen. Therefore, as a result of the replacement of four O molecules in hemoglobin₂ for four molecules of CO₂ the blood becomes dark in color with a cherry tint (venous blood). Illustration: “Iron metabolism in the body.” Iron metabolism in the body. A balanced diet contains enough iron to meet the daily requirement, which averages 10-20 mg. 1-2 mg is usually absorbed in the intestine. Iron absorption increases if it is necessary to compensate for the resulting deficiency, for example, with physiological blood loss in women. Iron is an important trace element that is involved in the work of many enzymes and is part of hemoglobin, a protein that carries oxygen from the lungs throughout the body. In addition, iron affects a person’s appetite, well-being, as well as the condition of his skin, hair and nails. The body cannot produce iron on its own, so it is important to get it from food or supplements. In this material, we will understand how iron deficiency manifests itself, how much iron the body needs at different periods, and what foods will help you get iron.

What happens when there is too little iron?

• Weakness, fatigue;
• Dizziness;
• Dyspnea;
• Heart palpitations;
• Brittle nails and hair;
• Pale skin.

This may be due to blood loss (for example, after blood donation or menstruation), an unbalanced diet, or the body’s inability to absorb enough iron from food. Lack of iron over time can lead to iron deficiency anemia, a condition in which the bone marrow cannot produce enough red blood cells due to iron deficiency. With anemia, the symptoms of iron deficiency intensify and worsen a person’s quality of life.

What happens when there is too much iron?

Excess iron can also harm the body. Taking too many iron supplements causes poisoning: symptoms include abdominal pain, dizziness and nausea.

Very high doses of iron can be fatal, especially if taken by children, so it is important to keep iron supplements out of the reach of children.

In addition, excess iron can promote tumor growth in the presence of cancer and increase oxidative stress, which underlies most pathological processes in the human body.

How are genetics and iron related?

Sometimes heredity can affect iron levels. Hemochromatosis is a genetic disease in which, due to a fault in one gene, the body absorbs much more iron. The trace element accumulates in the liver, heart and pancreas, which can subsequently damage these organs. However, while many people with hemochromatosis do not develop symptoms throughout their lives, others develop symptoms such as joint pain, abdominal pain and weakness in their 30s and 40s. Treatment consists of medications that help remove iron and bloodletting.

Studies show that the genes TMPRSS6, HFE and TFR2 are associated with iron levels. The TMPRSS6 and HFE genes, for example, help control levels of hepcidin, a protein that is responsible for iron balance in the body. If iron levels in the blood become low, the protein is produced more slowly and a person absorbs more iron from food. And another gene – TFR2 – helps activate hepcidin and is sometimes involved in the absorption of iron by cells.

The Atlas genetic test helps determine the carrier status of hemochromatosis and the likelihood of transmitting the disease to next generations. In addition to genetic diseases, the test will also determine how your genotype affects iron absorption.

Iron for children and pregnant women

During pregnancy, the volume of blood in a woman’s body increases. This allows the fetus to be provided with oxygen and essential nutrients. The amount of iron remains the same, and it becomes insufficient. It is important for pregnant women to get more iron than usual to avoid iron deficiency anemia. Iron deficiency can lead to premature birth, low birth weight and postpartum depression. With anemia, a woman feels constant drowsiness and fatigue due to lack of oxygen, but after childbirth few people pay attention to this, because caring for a baby also causes lack of sleep and loss of strength.

Iron deficiency anemia: who is at risk and how to prevent the disease?

In childhood, the body grows actively and also needs more iron than in adulthood. Children at risk of developing iron deficiency include those who:

• were born prematurely or had low birth weight;
• Drink cow’s or goat’s milk before the age of 1 year and consume more than 700 ml of milk in toddlerhood. Cow’s milk has been linked to the risk of iron deficiency anemia because, when consumed in excess, it impedes the absorption of iron.
• Do not receive iron in complementary foods after 6 months;
• A mixture not enriched with iron is obtained;
• Have chronic diseases or adhere to a strict diet;
• They don’t eat enough iron-rich foods;
• Are overweight or obese.

How much iron does my body need and how do I know if I’m eating enough iron?

Here you can rely on the recommended iron intake. It depends on age, gender and health status. The iron requirement for infants 4-6 months is 7 mg, and from 1 year to 7 years – 10 mg. During puberty, from 14 to 18 years of age, girls need 18 mg of iron per day, and men – 15 mg.

Women lose blood every month during their menstrual cycle, so between the ages of 19 and 50 they need 18 mg of iron daily, while men of the same age can get by with just 10 mg.

During pregnancy, a woman needs to receive 15 mg of iron per day. To get enough iron from food, you can eat 110 grams of chicken liver (12,8 mg), 200 grams of sautéed spinach (2 mg), 100 grams of boiled lentils (3,3 mg) and 3/4 of a high cocoa chocolate bar (9 mg).

A person may need more iron if they have kidney failure, an ulcer, or a gastrointestinal disorder that may prevent the body from absorbing iron. People who exercise a lot and vegetarians also need to consume more iron. Athletes need more iron because intense training can destroy red blood cells, and vegetarians need more iron because iron from plant foods is less absorbed. To obtain the daily requirement of iron, a vegetarian man needs to have an omelette (0,74 mg) with broccoli (1,59 mg) for breakfast and eat 100 grams of tofu (4,9 mg) with buckwheat (0,8 mg) for lunch or dinner, supplemented meals with tomato or orange juice for better absorption.

What foods are high in iron?

There are two types of iron: heme and non-heme. Heme iron is better absorbed and can be found in meat, fish and seafood. Non-heme iron is less bioavailable to the body and is found in nuts, vegetables and grain products. It is absorbed better when consumed with meat, fish or seafood.

If you take iron-containing foods and medications with vitamin C, the iron will also be absorbed better. The same effect can be achieved if you simply combine them with foods containing vitamin C – oranges, strawberries, kiwi, peppers, parsley, cabbage or tomatoes.

Some polyphenols and phytate, an acid that reduces nutrient absorption, have the opposite effect on iron absorption. Iron absorption can be affected by polyphenols, which are found in, for example, black tea, chili, lentils and eggplant, while phytates can be found in corn, bran or beans. Calcium can also reduce the bioavailability of iron, so if you want to get more iron, don’t drink a lot of milk during the day. It is important to understand that you should not completely avoid foods that reduce iron absorption – their effects are weakened with a balanced diet and do not significantly affect iron levels in most people.

Foods high in iron:

• Oysters;
• By-products: liver, tongue, kidneys, stomachs;
• Red meat: beef, lamb, pork;
• Fish: salmon, tuna;
• Dark chocolate;
• Beans;
• Chickpeas, peas, lentils;
• Spinach;
• Whole grains: wheat, oatmeal, brown rice;
• Tofu cheese;
• Nuts;
• Dried fruits: dried apricots, prunes, raisins.

Proper nutrition will help avoid iron deficiency anemia, but if a person already has this disease, then, most likely, just a proper diet will not be enough. If necessary, the doctor will prescribe special medications in the form of tablets, supplements or injections. Do not take iron supplements without consulting your doctor to avoid iron overload.

• Iron enters the body only through food or supplements. Its main source is red meat and offal.
• Both high and low iron levels can have negative health effects.
• On average, an adult woman needs 18 mg of iron per day, while a man needs only 10.
• The bioavailability of iron is increased by foods with vitamin C, but polyphenols, phytates and calcium can, on the contrary, reduce it.

• MedlinePlus, Iron, 2021
• MedlinePlus, Iron in diet, 2021
• MedlinePlus, Anemia caused by low iron – infants and toddlers, 2020
• MedlinePlus, Hemochromatosis, 2020
• NHS, Iron deficiency anemia, 2021
• NHS, Iron Vitamins and minerals, 2020
• Lab Tests Online, Iron, 2021
• Mayo Clinic, Iron deficiency anemia, 2019
• Mayo Clinic, Iron deficiency anemia during pregnancy: Prevention tips, 2019
• Mayo Clinic, Iron deficiency in children: Prevention tips for parents, 2019
• NIH, Iron Fact Sheet for Health Professionals, 2021
• US DEPARTMENT OF AGRICULTURE, FoodData Central, 2021