Dietary Iron Uptake and Absorption

Abstract

Iron is an essential element that participates in many physiological roles in the human body, including oxygen transport, DNA synthesis, cell division and differentiation, immunity, and electron transport. Iron absorption takes place primarily on the duodenum of the small intestine through the enterocyte cell. Its levels in the human body are controlled only by absorption since unlike most other essential nutrients, it has no regulated excretory system in humans. Hence, maintenance of iron level is critical to avoid adverse physiological consequences of iron deficiency or overload. Dietary iron exists in two forms; haem and non-haem; the bioavailability of these forms of iron is dependent on dietary inhibitors (calcium, phytates, and polyphenols) and enhancers (ascorbic acid). The mechanism that regulates iron absorption occurs in three stages; (i) luminal uptake and transport of iron across the apical membrane (ii) transfer of iron to the basolateral membrane and (iii) transport of iron across the basolateral membrane into circulation. The proteins that mediate iron uptake at the various stages include divalent metal transporter I, ferroportin, hephaestin, and hepcidin. This chapter will elaborate on dietary iron in its different forms, factors that enhance and inhibit iron absorption, the mechanism by which it is absorbed and iron supplementation and fortification.