Scientific Publications
Alginate Inhibits Iron Absorption from Ferrous Gluconate in a Randomized Controlled Trial and Reduces Iron Uptake into Caco-2 Cells
PLoS ONE, 9, e112144
Previous in vitro results indicated that alginate beads might be a useful vehicle for food iron fortification. A human study was undertaken to test the hypothesis that alginate enhances iron absorption by binding ferrous iron and preventing oxidation to ferric iron. A randomised, single blinded, cross-over trial was carried out in which iron absorption was measured from plasma iron appearance after a test meal. Overnight-fasted volunteers (n=15) were given a test meal of 200g cola-flavoured jelly plus 21 mg iron as ferrous gluconate, either in alginate beads mixed into the jelly or in a capsule. A sub-group (n=8) were given the test meals together with 600 mg calcium in order to determine whether alginate modified the inhibitory effect of calcium. Iron absorption was lower from the alginate beads than from ferrous gluconate (8.5% and 12.6% respectively, p=0.0025). As predicted, 600 mg calcium reduced iron absorption; it fell from 11.4% to 5.9% (p<0.001) with ferrous gluconate (55% reduction), and from 8.4% to 5.0% (p=0.0213) with alginate beads (39% reduction). Further in vitro studies in Caco-2 cells, to explore the reasons for the difference between the previous in vitro findings and the human study, confirmed the inhibitory effect of alginate. Beads similar to those used in the human study were subjected to simulated gastrointestinal digestion, with and without cola jelly, and the digestate applied to Caco-2 cells. Both alginate and cola jelly significantly reduced iron uptake into the cells (by 34%, p=0.0086 and 35%, p=0.003 respectively). The combination of cola jelly and calcium produced a very low ferritin response, one fifth (p<0.0001) of that observed with ferrous gluconate alone. The results of these studies demonstrate that alginate beads are not a useful delivery system for soluble salts of iron for the purpose of food fortification.
PLoS ONE, 9, e112144
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