Iron is essential to nearly all known organisms. In cells, iron is most often found in the center of proteins, but iron also binds to many other parts of the cell. An iron deficiency can lead to iron deficiency anemia. Iron is an important metal in animals, plants, and fungi and they all need a steady supply of it at all times. In mammals, iron distribution is very important because iron has a high possibility for being toxic. Distribution is also very important because most bacteria require iron, so restricting its availability to bacteria can help prevent infections.. This is probably the reason for low amounts of iron in mammalian milk.
Good sources of dietary iron include red meat, fish, poultry, leaf vegetables, tofu, peas, and fortified bread. Iron in meat is more easily absorbed than iron in vegetables, but hemoglobin from red meat may increase the rate of cancer. Iron provided by dietary supplements is often iron (II) fumarate, although iron sulfate is cheaper and is absorbed just as well. Even though elemental iron is absorbed to a much smaller extent, it is often added to foods such as enriched wheat flour.
Iron is most available to the body when binded to amino acids, this type of iron is 10-15 times more available to the body than any other, and is also available for use as a iron supplement. The amino acid is chosen for this purpose because it is the cheapest and most commonly found.
Excessive iron can be toxic, because iron reacts with peroxides and it is highly reactive and can damage DNA, proteins, and other cellular parts. Iron toxicity occurs when there is free iron in the cell, which occurs when iron levels exceed the capacity. Iron uptake is very regulated by the body, which has no means of excreting iron. Only small amounts of iron are lost daily through skin cells, so control of iron levels is mostly by regulating uptake.
Large amounts of ingested iron can cause high levels of iron in the blood because high iron levels can damage the cells of the intestines, preventing them from watching iron absorption, high blood contents containing iron can damage cells in the heart, liver and other places, which can cause serious problems, including organ damage and even death. Animals experience iron toxicity above 20 milligrams of iron for every kilogram of weight, and 60 milligrams per kilogram can kill. Over-consumption of iron, is often the result from eating large amounts of ferrous sulfate tablet supplements. Excessive iron intake can result in a iron overload disorder called hemochromatosis.