Iron: Basic Nutritional Aspects

Abstract One of the most abundant elements on earth is iron. Iron is an essential micronutrient but is toxic at high levels. Both iron deficiency and overload affect human health, and iron homeostasis is highly regulated to avoid disease. Oxygen delivery and energy metabolism represent iron’s primary physiological functions. As a transition metal, both ferrous (Fe 2+ ) and ferric (Fe 3+ ) forms of iron function in many oxidation/reduction reactions in human metabolism. Dietary heme provides a more bioavailable source of iron, while intestinal absorption of nonheme iron is tightly controlled by the iron-regulatory hormone hepcidin. Absorption of iron is promoted by ascorbic acid (vitamin C) but can be inhibited by a number of different dietary factors, including polyphenol-containing compounds (tea) and high calcium (milk). As molecular information rapidly emerges about the transport and metabolic disposition of iron after dietary absorption, important advances in our understanding of iron nutrition are being established.