Iron status and food matrix strongly affect the relative bioavailability of ferric pyrophosphate in humans

Abstract

Background Although ferric pyrophosphate is a promising compound for iron fortification of foods, there are few data on the effect of food matrices, processing, and ascorbic acid on its bioavailability. Objective We compared the relative bioavailability (RBV) with respect to ferrous sulfate of an experimental form of micronized dispersible ferric pyrophosphate (MDFP) in a wheat-based infant cereal given with and without ascorbic acid to the RBV of MDFP from a processed and unprocessed rice meal. Design Using a crossover design, iron absorption was measured in young women (n=26) from test meals fortified with isotopically labeled [57Fe]-MDFP and [58Fe]-ferrous sulfate, based on erythrocyte incorporation of stable isotope labels 14 days later. Results Geometric mean iron absorption from the wheat-based meal fortified with MDFP was 2.0 compared to 3.2% for ferrous sulfate (RBV=62). Addition of ascorbic acid at a 4:1 molar ratio to iron increased iron absorption from MDFP to 5.8% and from ferrous sulfate to 14.8% (RBV=39). In the rice meals, mean iron absorption from MDFP added to the rice at time of feeding was 1.7% compared to 11.6% for ferrous sulfate (RBV=15). The mean iron absorption from MDFP extruded into artificial rice grains was 3.0% compared to 12.6% from ferrous sulfate (RBV=25). Sixteen subjects of 26 were iron deficient. Iron status was a highly significant predictor of the RBV of MDFP (P<0.001). Conclusion RBV of the experimental MDFP varied markedly with food matrix and iron status. Assigning a single RBV to poorly soluble compounds may be of limited value in evaluating their suitability for food fortification.