OBJECTIVETo study the effects of ascorbic acid and citric acid on iron bioavailability using an in vitro digestion/Caco-2 cell culture model and evaluate the validity of this cell model.

METHODSThis model combined in vitro digestion technique with Fe uptake by Caco-2 cells by utilizing an inserted ring attached to a dialysis membrane to simulate the gastrointestinal environment to allow simultaneous food digestion and uptake processes. Ferritin formation in the Caco-2 cells was measured as the indicator of Fe uptake by exposing Caco-2 cells to the digests containing Fe plus ascorbic acid or citric acid.

RESULTSWhen Fe concentration in the digest was below 100 micromol/L, ferritin formation increased with the Fe concentration in the digest. The iron digest containing ascorbic acid exhibited a significant increase in ferritin formation relative to the iron digest containing citric acid. The model was more sensitive to lower iron concentrations when ascorbic acid was present in the digest, while wider range of iron concentration could be assessed by addition of citric acid.

CONCLUSIONSThe in vitro digestion/ Caco-2 cell culture model is a valuable tool for iron bioavailability assessment. Ascorbic acid has a stronger effect than citric acid in promoting iron bioavailability.