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.