Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: Inhibition of Iron Uptake by Phytic Acid, Tannic Acid and Zncl2: Studies Using An in Vitro Digestion/caco-2 Cell Model

Authors
item GLAHN, RAYMOND
item Wortley, Gary - CORNELL UNIVERSITY
item South, Paul - CORNELL UNIVERSITY
item Miller, Dennis - CORNELL UNIVERSITY

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 1, 2001
Publication Date: N/A

Interpretive Summary: The objective of this study was to document the effects of phytic acid, tannic acid and zinc on iron uptake using a cell culture model that simulates the digestion and uptake of iron in the human digestive tract. Common food components such as phytic acid, tannic acid and zinc are known to inhibit iron uptake in humans. This study documented similar inhibitory yeffects in this model system. For example, the results demonstrated that both phytic acid and tannic acid profoundly inhibit intestinal iron uptake, with tannic acid being the more potent inhibitor. Zinc chloride also inhibited iron uptake in this model, suggesting that consuming both minerals simultaneously, possibly as a supplement without the presence of foods, may result in lower iron uptake from the supplement dose. Overall, the results agree with studies in humans and demonstrate the relative effects of these compounds on iron uptake in this model system. Studies such as this will provide key information for determining iron availabilit under more complex meal conditions.

Technical Abstract: The objective of this study was to document the effects of phytic acid, tannic acid and zinc on iron uptake in an in vitro digestion/Caco-2 cell culture model. The effects of phytic acid and tannic acid on iron uptake were measured at increasing molar ratios of FeCl3 : phytic acid or tannic acid. Maximal inhibition of iron uptake by phytic acid occurred at a 1:10 ratio of Fe to phytic acid. Dialyzable Fe decreased at low Fe to phytic acid ratio, but increased at Fe:phytic acid ratios greater than 1:3 indicating that more iron was soluble at higher phytic acid levels, but less available. As in human studies, heme iron was less inhibited by phytic acid than nonheme iron. Tannic acid was a more potent inhibitor of nonheme iron uptake, as maximal inhibition (97.5%) of iron uptake occurred at a ratio of 1:1 or less. The addition of ZnCl2 to the digest at ratios of 1:0.5 and 1:1 decreased iron uptake by 57% and 80%, respectively. Overall, the results agree qualitatively with studies in humans and demonstrate the relative effects of these compounds on iron uptake in this model system. Studies such as this will provide key information for determining iron availability under more complex meal conditions.

Last Modified: 9/10/2014
Footer Content Back to Top of Page