Human iron metabolism

Iron is an essential nutrient for human beings, although it can also be toxic. The most important role is in the heme protein of hemoglobin, although it has other trace functions.

Digestion
Iron, in food, is processed differently depending if it is in the form of heme (e.g., in meats) or in other molecules.

Some molecular iron, in fact, is not in a form that can be metabolized.