Green tea or rosemary extract added to foods reduces nonheme-iron absorption123

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ABSTRACT

Background:

Phenolic compounds act as food antioxidants. One of the postulated mechanisms of action is chelation of prooxidant metals, such as iron. Although the antioxidative effect is desirable, this mechanism may impair the utilization of dietary iron.

Objective:

We sought to determine the effect of phenolic-rich extracts obtained from green tea or rosemary on nonheme-iron absorption.

Design:

Young women aged 19–39 y consumed test meals on 4 separate occasions. The meals were identical except for the absence (meal A) or presence (meal B) of a phenolic-rich extract from green tea (study 1; n = 10) or rosemary (study 2; n = 14). The extracts (0.1 mmol) were added to the meat component of the test meals. The meals were extrinsically labeled with either 55Fe or 59Fe and were consumed on 4 consecutive days in the order ABBA or BAAB. Iron absorption was determined by measuring whole-body retention of 59Fe and the ratio of 55Fe to 59Fe activity in blood samples.

Results:

The presence of the phenolic-rich extracts resulted in decreased nonheme-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 extract.

Conclusion:

Phenolic-rich extracts used as antioxidants in foods reduce the utilization of dietary iron.

KEY WORDS

Iron absorption
antioxidants
phenolic compounds
green tea
rosemary
radioisotopes
chelation
food preservatives
rosmarinic acid
carnosol
carnosic acid
epicatechin gallate
epigallocatechin gallate
epigallocatechin
gallic acid
epicatechin
catechin
women

Cited by (0)

1

From the Research Department of Human Nutrition, LMC Centre for Advanced Food Studies, The Royal Veterinary and Agricultural University, Frederiksberg, Denmark; the Human Nutrition Unit, Department of Biochemistry, University of Sydney, Sydney, Australia; the Department of Biochemistry and Nutrition, Technical University of Denmark, Lyngby, Denmark; and the Department of Clinical Physiology and Nuclear Medicine, The National University Hospital, Copenhagen.

2

Supported by the Danish Ministry of Education under the Food Technology Research Program (FOETEK).

3

Address reprint requests to S Samman, Human Nutrition Unit, Department of Biochemistry, University of Sydney, NSW 2006 Australia. E-mail: [email protected].