A Review of Nutrients and Compounds, Which Promote or Inhibit Intestinal Iron Absorption: Making a Platform for Dietary Measures That Can Reduce Iron Uptake in Patients with Genetic Haemochromatosis

Figure 1

Mechanisms of intestinal iron absorption. Most iron is absorbed in the duodenum and proximal jejunum due to the acidic pH of the intestinal content. More, distally in the jejunum, pH becomes neutral or alkaline, and iron uptake declines. Nonheme food iron Fe³⁺ enters the nonheme iron pool and heme iron enters the heme iron pool. Fe³⁺ is reduced to Fe²⁺ by duodenal cytochrome B and subsequently enters the luminal side of the enterocyte by the iron importer DMT-1 pathway. Fe²⁺ is transferred to the basolateral side of the enterocyte, effluxed by the iron exporter ferroportin, and subsequently oxidized to Fe³⁺ by hephaestin and transferred to the carrier protein transferrin in the blood plasma. Part of the iron enters the intracellular ferritin iron pool and is lost by desquamation of the enterocyte into faeces. Hepcidin from the liver inactivates ferroportin, thereby inhibiting iron uptake. Heme iron is absorbed within the intact protoporphyrin ring by a separate pathway possibly involving a heme transporter and heme oxygenase. Figure adapted with permission from [27].