Health effects of iron

Chronic iron deficiency leads to a condition called anemia. Anemia describes a low concentration of red blood cells and/or hemoglobin in the blood. Different types of anemia can be defined depending on their origin and specific features. In a limited number of cases, anemia develops as a consequence of disease, such as renal failure or certain endocrine disorders. However, most cases of anemia are related to a deficiency in a specific micronutrient, such as folate, vitamin B12, and especially iron. Indeed, iron deficiency is the most common cause of anemia across the world. The shape of the red blood cells (bicon-cave disk or abnormal forms), size (microcytic, normocytic, or macrocytic) and color intensity (hypochromic, normochromic, or hyperchromic) are used to diagnose the origin of the anemia. Iron deficiency anemia is characterized by microcytic (meaning small cell) and hypochromic (meaning pale color) red blood cells.
People that suffer from iron-deficiency anemia often complain of fatigue, weakness and low physical endurance. These symptoms are directly related to the low hemoglobin concentration in the blood and the reduced capacity to transport oxygen to the tissues. Iron deficiency may also lead to reduced cognitive performance and immunity, increasing the risk of infections. Because of these symptoms, iron deficiency has a huge impact on quality of life and work productivity in many countries, especially in women.
The main cause of iron-deficiency anemia is consumption of a diet that is poor in (bioavailable) iron. In addition, iron-deficiency is often related to bleeding. In Western and developing countries, groups of people that are at risk for iron-deficiency anemia include women who menstruate, particularly if menstrual periods are heavy, women who are pregnant or who have recently given birth, vegetarians/vegans, and other people whose diets may be low in iron. In addition, people that suffer from a variety of physical ailments are at increased risk of iron-deficiency anemia. In developing countries, iron-deficiency anemia is also common in children. It is often caused by infections of parasitic worms that cause intestinal bleeding, in combination with a low iron diet. 

Iron content in foods

Iron is present in a great variety of foods. Some foods are excellent sources of iron, whereas other foods are mediocre or poor sources. The best sources of iron are foods made from blood such as black pudding. Other excellent sources are liver and red meat. In general, the darker the color of the meat, the higher the iron content. Thus, steak provides more iron than chicken breast. Many plant-based foods also contain substantial amounts of iron. This includes all sorts of beans (soybeans, black beans, pinto beans, garbanzo beans etc) and various types of grains (oats, wheat, rice etc). For grains it should be realized that most of the iron is present in the germ and is removed during processing. Accordingly, white rice is a poor source of iron, whereas brown rice is a good source. Similarly, white bread is low in iron, whereas whole wheat bread contains plenty of iron. Because most of the iron is removed during processing, several countries add iron to white bread and white flour to restore it to the level found in whole wheat bread and whole wheat flour.

In general, iron present in foods in the form of heme, the so-called heme iron, is much better absorbed into the body than non-heme iron. Heme iron is only found in animal foods. For this reason, animal foods are considered a better source of iron than plant foods. The iron present as non-heme iron can either be in the divalent (Fe2+, ferrous iron) or trivalent (Fe3+, ferric iron) form. Fe3+ needs to be converted into Fe2+ before it can be absorbed into the body.
The absorption of iron can be influenced by other food components. As for calcium, metal-binders such as oxalate and phytate may hinder iron uptake. It is difficult to give an estimate of the relative absorption of iron from a food. That is because the relative rate of iron absorption is highly influenced by someone’s iron status. People that have a low iron status will absorb more iron from a particular food compared to people with a high iron status. The underlying mechanism will be explained in more detail later. First, we need to examine how iron is stored and processed in the body.