Nanopowders Improve Iron Bioavailability

Nanostructured iron- and zinc-containing compounds are highly bioavailable in rats but don’t accumulate in their tissues, making the nanomaterials a promising means of fortifying foods, according to a study (Nat. Nanotechnol., DOI: 10.1038/nnano.2010.79). Iron fortification of foods is difficult because easily absorbed water-soluble compounds can change the color or taste of foods, whereas poorly water-soluble compounds have limited bioavailability. Michael B. Zimmermann of the Swiss Federal Institute of Technology, Zurich, and coworkers added nanopowders of poorly soluble phosphates and oxides containing both iron and zinc to rat food, including two oxides doped with either calcium or magnesium. When rats ate the food, the bioavailability of the iron was comparable with that of FeSO₄, a highly soluble compound used to fortify human food. The magnesium in particular lightened the dark-brown color of the oxide and improved the bioavailability of the iron. Iron didn’t accumulate in the gastrointestinal tract or other tissues of the rats, and histological analyses revealed no significant structural changes in most tissues, the researchers report. They note that further research is still needed to rule out potential toxicity of the nanomaterials.