Effects of ascorbic acid, phytic acid and tannic acid on iron bioavailability from reconstituted ferritin measured by an in vitro digestion-Caco-2 cell model

The effects of ascorbic acid (AA), phytate and tannic acid (TA) on Fe bioavailability from Fe supplied as reconstituted ferritin were compared with FeSO(4) using an in vitro digestion-Caco-2 cell model. Horse spleen apoferritin was chemically reconstituted into an animal-type ferritin (HSF) and a plant-type ferritin (P-HSF) according to the typical ratios of Fe:P found in these molecules. In the presence of AA (Fe:AA molar ratio of 1:20), significantly more Fe was absorbed from FeSo(4) (about 303%), HSF (about 454%) and P-HSF (about 371%) when compared with ferrous sulfate or ferritin without AA. Phytic acid (PA; FeTA molar ratio of 1:20) significantly reduced Fe bioavailability from FeSo(4) (about 86%), HSF (about 82%) and P-HSF (about 93%) relative to FeSO(4) and the ferritin controls. Treatment with TA (Fe:TA molar ratio of 1: 1) significantly decreased Fe bioavailability (about 97%) from both FeSo(4) and the ferritin samples. AA was able to partially reverse the negative effect of PA (Fe:PA:AA molar ratio of 1:20:20) on Fe bioavailability but did not reverse the inhibiting effect of TA (Fe:TA:AA molar ratio of 1: 1:20) on Fe bioavailability from ferritin and FeSO(4). Overall, there were no significant differences in bioavailable Fe between P-HSF, HSF or FeSO(4). Furthermore, the addition of AA (a known promoter) or the inhibitors, PA and TA, or both, did not result in significant differences in bioavailable Fe from ferritin relative to FeSO(4). The results suggest that Fe in the reconstituted ferritin molecule is easily released during in vitro digestion and interacts with known promoters and inhibitors.