Ascorbic acid does not offset the inhibitory effect of bioactive dietary polyphenolic compounds on heme iron absorption in human intestinal Caco‐2 cells

Abstract

Heme iron is an important source of dietary iron but its absorption mechanism has not been completely elucidated. Recently, bioactive dietary polyphenols have been attracting more and more attention due to their reported health benefits. We previously reported that (−)‐epigallocatechin‐3‐gallate (EGCG) and grape seed extract (GSE) inhibit heme iron absorption by reducing basolateral iron export rather than by decreasing apical heme iron uptake in intestinal cells. In current studies, we determined the effect of three dietary polyphenols, green tea extract (GTE), EGCG and GSE, on heme iron absorption in human intestinal cells and tested whether ascorbic acid counteracts the inhibitory effects of polyphenols on heme iron absorption. The results demonstrated that GTE, EGCG and GSE all strongly reduced basolateral iron transport. Addition of ascorbic acid to polyphenol treatment stimulated apical heme iron uptake but did not reverse the decreased basolateral iron transport. These results suggest that the inhibitory effects of bioactive polyphenolic compounds on heme iron absorption cannot be offset by ascorbic acid.