Effects of common beans and by-products of fermentation of prebiotics on iron bioavailability in pig and Caco-2 cell models

Inulin supplementation appears to enhance iron absorption but the mechanism is unknown. Our objective was to understand how inulin fermentation by-products like short chain fatty acids (SCFAs) affect iron bioavailability. In a Caco-2 cell culture model, cells were exposed to mixtures of 10 muM FeSO4 or FeCl3 with 500 or 1000 muM organic acids that included ascorbic, citric, acetic, propionic, lactic and butyric acids prepared in pH 7.0 MEM for 1 hr or 24 hr. Ferritin formation was measured as an index of cellular iron uptake by Caco-2 cells. In the 1 hr treatments, FeSO4 uptake increased by 3.4 fold and 2 fold in the presence of ascorbic and propionic acid, respectively; FeCl3 uptake increased multiple folds in the presence of ascorbic and acetic acids. No significant increase in Fe uptake was shown in the remaining treatments. In the 24 hr treatments, all treatments had high iron uptake but were lower than the Fe-only controls. When cells were pretreated with organic acids for 24 hr before exposure to Fe for 1 hr, propionic acid pretreatment at 500 muM enhanced FeSO4 uptake, but not at 1000 muM. Butyric and acetic acids pretreatments at 500 and 1000 muM enhanced FeCl3 uptake. In summary, SCFAs enhance Fe uptake and may be part of the mechanism for inulin enhancing iron absorption but more research is necessary.; Although SCFAs produced during fermentation of inulin might enhance iron absorption, sulfide produced in the colon by sulfur-reducing bacteria can precipitate soluble iron and inhibit iron absorption. Our objective was to determine iron solubility and iron bioavailability in the presence of sulfide and decreasing pH in a Caco-2 cell model. Mixtures of FeSO4 or FeCl3 (30 muM) with Na2S (0, 75, 150, 300 and 450 muM) were prepared in MEM (pH 5.8, 6.4 and 7.0). FeSO4 and FeCl 3 remained soluble in sulfide solutions, however up to 65 % of FeSO 4 was oxidized while up to 50% of FeCl3 was reduced to Fe 2+ with increasing sulfide and pH. Iron uptake from FeSO4 and FeCl3 increased with increasing pH and sulfide concentration up to 150 or 300 muM. Low concentrations of sulfide did not reduce iron solubility or cellular iron uptake.; Beans are good sources of iron however polyphenols in beans may affect iron bioavailability. Analysis showed the red beans had higher phenolic concentrations than white beans but there was no difference between the bean diets. Bean diets were prepared and their iron bioavailability was assessed in a Caco-2 cell and piglet model. Iron bioavailability from the white bean diet was not higher than the red bean diet in the first Caco-2 cell experiment, but was higher from the white bean diet than the red bean diet in the second Caco-2 cell experiment. In pig studies 1 and 2, the piglets grew equally well and iron repletion was similar in both groups. Proline-rich protein gene expression was upregulated in the red bean diet group and this upregulation is a likely adaptation to the red bean polyphenols. Since iron bioavailability from red and white beans in diets was not different, polyphenols in beans may not be a major inhibitor of iron absorption.