Fortification of foods with nano-iron: its uptake and potential toxicity: current evidence, controversies, and research gaps

Abstract

Iron fortification is a very popular practice in several countries, particularly in countries in which a large proportion of the population is suffering from iron deficiency, as in lower-middle-income countries. Food fortification with iron salts is a difficult operation, because most iron complexes (ferrous sulfate, ferrous chloride) are water soluble, which can cause undesirable alterations to the sensory properties of the food carriers. On the other hand, insoluble iron salts (eg, ferric pyrophosphate) do not have an unpleasant taste or color, but their bioavailability is low. These issues can be addressed with iron nanoparticles. The small particle size has been shown to have a significant impact on iron absorption. Iron nanoparticles with smaller particle sizes have more surface area, which improves their solubility in gastric juice and leads to better bioavailability. When compared with water-soluble iron complexes, nano-sized iron compounds generate negligible organoleptic alterations in food carriers. As a result, iron nanoparticles could be potentially used in food fortification to minimize iron-deficiency anemia. This review focuses on the absorption pathway and the toxicity of various forms of iron nanoparticles. In vitro cell studies and animal studies indicate that nano-sized iron particles can be taken up either by the Divalent Metal Transporter 1 pathway or the endocytic pathway. Nano-sized ferric phosphate and iron(III) oxo hydroxide show the most promising results, based on recent studies on fortification. To date, there are insufficient studies on the maximum intake level and potential adverse effects. Further extensive work is essential before introducing nano-iron compounds as food fortificants.

Keywords: absorption pathway; iron; nanoparticles; toxicity.