Comparing soluble ferric pyrophosphate to common iron salts and chelates as sources of bioavailable iron in a caco-2 cell culture model

Authors: ZHU, LE - University Of Wisconsin; Glahn, Raymond; NELSON, DEANNA - Cornell University; MILLER, DENNIS - Cornell University

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2009
Publication Date: 6/9/2009
Citation: Zhu, L., Glahn, R.P., Nelson, D., Miller, D.D. 2009. Comparing soluble ferric pyrophosphate to common iron salts and chelates as sources of bioavailable iron in a caco-2 cell culture model. Journal of Agricultural and Food Chemistry. 57(11):5014-5019.

Interpretive Summary: Iron bioavailability from supplements and fortificants varies depending upon the form of the iron and the presence or absence of iron absorption enhancers and inhibitors. A model for digestion has been developed in our lab that uses a simulated digestion and Caco-2 epithelial tissue cell culture monolayer to imitate the intestinal lining and absorption of minerals into our bodies. Using our model system, our objectives were to compare the effects of pH and selected enhancers and inhibitors and food matrices on the bioavailability of iron in soluble ferric pyrophosphate (SFP) to other iron fortificants using a Caco-2 cell culture model with or without the combination of in vitro digestion. Our results suggest that dietary factors known to enhance and inhibit iron bioavailability from various iron sources affect iron bioavailability from SFP in similar directions. However, the magnitude of the effects of iron absorption inhibitors on SFP iron appears to be smaller than on iron salts, such as ferrous sulphate and ferric chloride. This supports the hypothesis that SFP is a promising iron source for food fortification and dietary supplements.

Technical Abstract: Iron bioavailability from supplements and fortificants varies depending upon the form of the iron and the presence or absence of iron absorption enhancers and inhibitors. Our objectives were to compare the effects of pH and selected enhancers and inhibitors and food matrices on the bioavailability of iron in soluble ferric pyrophosphate (SFP) to other iron fortificants using a Caco-2 cell culture model with or without the combination of in vitro digestion. Ferritin formation was the highest in cells treated with SFP compared to those treated with other iron compounds or chelates. Exposure to pH 2 followed by adjustment to pH 7 markedly decreased FeSO4 bioavailability but had a smaller effect on bioavailabilities from SFP and sodium iron(III) ethylenediaminetetraacetate (NaFeEDTA), suggesting that chelating agents minimize the effects of pH on iron bioavailabilty. Adding ascorbic acid (AA) and cysteine to SFP in a 20:1 molar ratio increased ferritin formation by 3- and 2-fold, respectively, whereas adding citrate had no significant effect on the bioavailability of SFP. Adding phytic acid (10:1) and tannic acid (1:1) to iron decreased iron bioavailability from SFP by 91 and 99%, respectively. The addition of zinc had a marked inhibitory effect on iron bioavailability. Calcium and magnesium also inhibited iron bioavailability but to a lesser extent. Incorporating SFP in rice greatly reduced iron bioavailability from SFP, but this effect can be partially reversed with the addition of AA. SFP and FeSO4 were taken up similarly when added to nonfat dry milk. Our results suggest that dietary factors known to enhance and inhibit iron bioavailability from various iron sources affect iron bioavailability from SFP in similar directions. However, the magnitude of the effects of iron absorption inhibitors on SFP iron appears to be smaller than on iron salts, such as FeSO4 and FeCl3. This supports the hypothesis that SFP is a promising iron source for food fortification and dietary supplements.