Iron is an important component of haemoglobin in red blood cells and it represents about two-thirds of the body's iron.  Haemoglobin carries oxygen from your lungs to every part of your body.  If you don't have enough iron, your body can't make enough healthy oxygen-carrying red blood cells. Your liver stores iron from haemoglobin in the form of ferritin, ready to make new red blood cells. This is why animal liver is such a good source of iron.

Iron is  is naturally present in many foods, added to some food products and available as a dietary supplement.

We typically only lose small amounts of iron in urine, faeces, the gastrointestinal tract, and via skin. The RDA for an adult male is 8mg and for a female it is 15mg. Pregnant women need 27mg+

The richest sources of heme iron in the diet include lean meat and seafood. Dietary sources of nonheme iron include nuts, beans, vegetables, and fortified grains. In Western countries, about half of dietary iron comes from bread, cereal and other grain products. Some plant-based foods that are good sources of iron, such as spinach, have low iron bioavailability because they contain iron absorption inhibitors.