What is iron?

Iron is a mineral that the body needs to make hemoglobin, the protein in red blood cells that carries oxygen from the lungs to the tissues.^[1] An adult body holds 3 to 4 g of iron, and most of it is in hemoglobin.^[1]

Food has two forms of iron. Heme iron comes from meat, seafood and poultry. Nonheme iron comes from plants and fortified foods.^[1] Supplements most often contain iron salts such as ferrous sulfate, ferrous gluconate, ferric citrate and ferric sulfate. Other forms include carbonyl iron, iron amino-acid chelates, heme iron polypeptides and polysaccharide-iron complexes.^[1]