Iron Absorption Mechanisms in Nutritional Contexts

Iron is an essential micronutrient involved in oxygen transport, cellular respiration and DNA synthesis. Dietary iron exists in two main forms: haem iron, derived from animal products and more readily absorbed, and non-haem iron, present in plant-based foods and subject to greater dietary modulation. In the duodenum, ferric iron (Fe3+) is reduced at the enterocyte surface by enzymes such as duodenal cytochrome b and then taken up as ferrous iron (Fe2+) via the divalent metal transporter 1. Within enterocytes, iron may be stored in ferritin or exported across the basolateral membrane by ferroportin, after which it is oxidised by hephaestin and bound to transferrin for systemic distribution. Hepcidin, a liver-derived hormone, orchestrates whole-body iron balance by inducing internalisation of ferroportin under conditions of iron sufficiency or inflammation, thereby reducing absorption. Dietary enhancers—particularly ascorbic acid and “meat factors”—promote non-haem iron solubility and uptake, whereas inhibitors including phytic acid, polyphenols and excess calcium form insoluble complexes that impede absorption. Understanding these interactions has global significance for addressing iron deficiency anaemia and devising context-specific strategies such as targeted food fortification, meal composition advice and processing techniques to optimise bioavailability in diverse populations.

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Iron Absorption Mechanisms in Nutritional Contexts publication trend

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Technical terms

Haem iron: Iron bound within the porphyrin ring of haemoglobin and myoglobin, predominantly found in animal tissues and absorbed efficiently.

Non-haem iron: Ionic iron in plant and fortified foods, whose solubility and uptake are influenced by dietary enhancers and inhibitors.

Bioavailability: The proportion of dietary iron that is released during digestion, absorbed into enterocytes and made available for physiological functions.

Phytic acid: A plant-derived phosphate storage molecule that chelates iron and other minerals, reducing their absorption.

Hepcidin: A peptide hormone produced by the liver that regulates systemic iron homeostasis by controlling ferroportin-mediated iron export.

Ferritin: An intracellular protein complex that stores iron within cells, serving as a marker of iron reserves.

References

1. Absorption of Iron Naturally Present in Soy. Advances in Nutrition (2025).
2. Content and Availability of Minerals in Plant-Based Burgers Compared with a Meat Burger. Nutrients (2023).
3. 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. Journal of Nutrition and Metabolism (2020).