Dietary iron depletion at weaning imprints low microbiome diversity and this is not recovered with oral nano Fe(III)

Alterations in the gut microbiota have been recently linked to oral iron. We conducted two feeding studies including an initial diet‐induced iron‐depletion period followed by supplementation with nanoparticulate tartrate‐modified ferrihydrite (Nano Fe(III): considered bioavailable to host but not bacteria) or soluble ferrous sulfate (FeSO4: considered bioavailable to both host and bacteria). We applied denaturing gradient gel electrophoresis and fluorescence in situ hybridization for study‐1 and 454‐pyrosequencing of fecal 16S rRNA in study‐2. In study‐1, the within‐community microbial diversity increased with FeSO4 (P = 0.0009) but not with Nano Fe(III) supplementation. This was confirmed in study‐2, where we also showed that iron depletion at weaning imprinted significantly lower within‐ and between‐community microbial diversity compared to mice weaned onto the iron‐sufficient reference diet (P