Iron from nanostructured ferric phosphate: absorption and biodistribution in mice and bioavailability in iron deficient anemic women

Food fortification with iron nanoparticles (NPs) could help prevent iron deficiency anemia, but the absorption pathway and biodistribution of iron-NPs and their bioavailability in humans is unclear. Dietary non-heme iron is physiologically absorbed via the divalent metal transporter-1 (DMT1) pathway. Using radio- iron isotope labelling in mice with a partial knockdown of intestine-specific DMT1, we assessed oral absorption and tissue biodistribution of nanostructured ferric phosphate (FePO(4)-NP; specific surface area [SSA] 98 m(2)g(-1)) compared to to ferrous sulfate (FeSO(4)), the reference compound. We show that absorption of iron from FePO(4)-NP appears to be largely DMT1 dependent and that its biodistribution after absorption is similar to that from FeSO(4), without abnormal deposition of iron in the reticuloendothelial system. Furthermore, we demonstrate high bioavailability from iron NPs in iron deficient anemic women in a randomized, cross-over study using stable-isotope labelling: absorption and subsequent erythrocyte iron utilization from two (57)Fe-labeled FePO(4)-NP with SSAs of 98 m(2)g(−1) and 188 m(2)g(−1) was 2.8-fold and 5.4-fold higher than from bulk FePO(4) with an SSA of 25 m(2)g(−1) (P < 0.001) when added to a rice and vegetable meal consumed by iron deficient anemic women. The FePO(4)-NP 188 m(2)g(-1) achieved 72% relative bioavailability compared to FeSO(4). These data suggest FePO(4)-NPs may be useful for nutritional applications.