ARS | Publication request: Meat and Ascorbic Acid Can Promote Fe Availability from Fe-Phytate But Not from Fe-Tannic Acid Complexes

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 19, 2005
Publication Date: December 28, 2005
Citation: Engle-Stone, R., Yeung, A., Welch, R.M., Glahn, R.P. 2005. Meat and ascorbic acid can promote fe availability from fe-phytate but not from fe-tannic acid complexes. Journal of Agricultural and Food Chemistry. 53:10276-10284.

Interpretive Summary: This study utilized an in vitro model to determine the levels of ascorbic acid (AA) and “meat factor” needed to promote Fe absorption from Fe complexed with phytic acid (PA) or tannic acid (TA). Knowledge of these effects is important to allow nutritionists and food scientists to understand the key factors affecting Fe bioavailability in the diet. Ascorbic acid reversed the inhibition of Fe absorption by phytic acid beginning at a molar ratio of 1:20:1 (Fe:PA:AA) but essentially had no effect on the Fe complexed with tannic acid. Fish also reversed the inhibition of Fe uptake by phytic acid but not by tannic acid. Tannic acid and fish decreased total Fe solubility. Iron in the presence of phytic acid was highly soluble. Ascorbic acid, but not fish, increased the percentage of soluble Fe as Fe2+ in the presence of both inhibitors. The results indicate that monoferric phytate is a form of Fe that can be available for absorption in the presence of uptake promoters. In contrast, a tannic acid-Fe complex is much less soluble and unavailable in the presence of promoters.

Technical Abstract: This study utilized an in vitro digestion/Caco-2 cell model to determine the levels of ascorbic acid (AA) and “meat factor” needed to promote Fe absorption from Fe complexed with phytic acid (PA) or tannic acid (TA). Ascorbic acid reversed the inhibition of Fe absorption by phytic acid beginning at a molar ratio of 1:20:1 (Fe:PA:AA) but essentially had no effect on the Fe complexed with tannic acid. Fish also reversed the inhibition of Fe uptake by phytic acid but not by tannic acid. Tannic acid and fish decreased total Fe solubility. Iron in the presence of phytic acid was highly soluble. Ascorbic acid, but not fish, increased the percentage of soluble Fe as Fe2+ in the presence of both inhibitors. The results indicate that monoferric phytate is a form of Fe that can be available for absorption in the presence of uptake promoters. In contrast, a tannic acid-Fe complex is much less soluble and unavailable in the presence of promoters.