The amount of iron in food or supplements that is absorbed and used by the body is influenced by the iron nutritional status of the individual and whether or not the iron is in heme form (the iron atom bound in the center of a large organic ring structure).
Individuals who are anemic or iron deficient absorb a larger percentage of the iron they consume (especially non-heme iron) than individuals who are not anemic and have sufficient iron stores (3, 7).
Heme iron comes mainly from hemoglobin and myoglobin in meat, poultry, and fish. It is more readily absorbed than non-heme iron and its absorption is less affected by other dietary factors. Although heme iron accounts for only 10–15% of the iron found in the diet, it may provide up to one third of total absorbed dietary iron.
Plants, dairy products, meat, and iron salts added to foods and supplements are all sources of non-heme iron. Its absorption is strongly influenced by enhancers (e.g., vitamin C, citric and lactic acid, meat, fish, and poultry) and inhibitors (e.g., phytic acid, polyphenols, and soy protein) present in the same meal (3, 7, 11,1).
Iron supplements are indicated for the prevention and treatment of iron deficiency. Individuals who are not at risk of iron deficiency (e.g., adult men and postmenopausal women) should not take iron supplements without an appropriate medical evaluation for iron deficiency. A number of iron supplements are available, and different forms provide different proportions of elemental iron (26).