The relative bioavailability in humans of elemental iron powders for use in food fortification

Background Bioavailability data in humans of elemental iron powders is limited although elemental iron is a common form of iron when used as a fortificant. Aim of the study The relative bioavailability (RBV) of seven elemental iron powders, five commercially available and two developmental are evaluated. In addition, one commercial electrolytic iron powder given with ascorbic acid (AA) was examined. Methods Based on a validated method this double-blinded randomized crossover study included three groups of male blood donors (n=3*16) who were served rolls fortified with different elemental iron powders or ferrous sulfate (FeSO4) nine weeks apart. Blood samples were drawn every hour for six hours. RBV was obtained by comparing the increase in serum iron concentration induced by the elemental iron with the increase induced by FeSO4. Results All elemental iron powders studied were significantly less well absorbed compared to FeSO4. The electrolytic iron given with 50-mg AA was as well absorbed as FeSO4 (molar ratio=1:6, AA:Fe). The mean RBVs of the iron powders were: electrolytic (A-131, RBV=0.65); electrolytic (Electrolytic, RBV=0.59); carbonyl (Ferronyl, RBV=0.58); H-reduced (AC-325, RBV=0.56); H-reduced (Hi-Sol, RBV=0.50); carbonyl (CF, RBV=0.37); reduced (Atomet 95SP, RBV=0.36). The reduced iron was distinguished by having significantly lower RBV (0.36) although no significant overall ranking was possible. Conlcusions Based on a validated method this double-blinded cross-over study in humans showed that the evaluated elemental iron powders currently available for commercial use are significantly less well absorbed compared to FeSO4. The results indicate that the reduced iron powder was absorbed to a lower extent compared to the other iron powders and only 36% compared to FeSO4. Ascorbic acid seems to improve the bioavailability of elemental iron even though a rather low molar ratio is used. Thus, if confirmed, this enhancing effect of ascorbic acid on elemental iron when used as a fortificant could be used by co-fortifying them.