Green tea or rosemary extract added to foods reduces nonheme-iron absorption

Background: Phenolic compounds act as food antioxidants. One of the postula ted mechanisms of action is chelation of prooxidant metals, such as iron. A lthough the antioxidative effect is desirable, this mechanism may impair th e utilization of dietary iron. Objective: We sought to determine the effect of phenolic-rich extracts obta ined from green tea or rosemary on nonheme-iron absorption. Design: Young women aged 19-39 y consumed test meals on 4 separate occasion s. The meals were identical except for the absence (meal A) or presence (me al B) of a phenolic-rich extract from green tea (study 1; n = 10) or rosema ry (study 2; n = 14). The extracts (0.1 mmol) were added to the meat compon ent of the test meals. The meals were extrinsically labeled with either Fe- 55 or Fe-59 and were consumed on 4 consecutive days in the order ABBA or BA AB. Iron absorption was determined by measuring whole-body retention of 59F e and the ratio of Fe-55 to 59Fe activity in blood samples. Results: The presence of the phenolic-rich extracts resulted in decreased n onheme-iron absorption. Mean (+/-SD) iron absorption decreased from 12.1 +/ - 4.5% to 8.9 +/- 5.2% (P < 0.01) in the presence of green tea extract and from 7.5 +/- 4.0% to 6.4 +/- 4.7% (P < 0.05) in the presence of rosemary ex tract. Conclusion: Phenolic-rich extracts used as antioxidants in foods reduce the utilization of dietary iron.