Iron is one of the most abundant minerals on Earth. It occurs naturally in various foods such as oysters, legumes, chocolate, spinach, beef, and potatoes, and is added to some foods (e.g., cereals) as a fortification measure. Iron is also sold as a supplement in the form of capsules, tablets, or liquid. In hospital settings, it can be administered through intravenous (IV) or intramuscular (IM) injection.[1]
Dietary iron comes in two primary forms: heme iron and non-heme iron. Heme iron is more readily absorbed; it is formed when iron binds to a heterocyclic organic compound called porphyrin. Heme iron is a component of hemoproteins like hemoglobin (Hb), an oxygen transport protein, and myoglobin, an oxygen-storage protein found in muscle tissues. Animal products (e.g., meat, poultry, and fish) contain both heme and non-heme iron, whereas plant-based and iron-fortified foods only provide non-heme iron, which is less easily absorbed by the body.[1]
Additionally, iron is a constituent of the iron-sulfur clusters (ISCs)[2] found in many proteins; iron is also present in proteins responsible for iron storage and transport (i.e., transferrin, lactoferrin, ferritin, hemosiderin).[3]