Submitted to: Nutrition Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/20/1998
Publication Date: N/A
Citation: Interpretive Summary: Iron deficiency anemia is a common debilitating disorder in children and premenopausal women. This nutritional disorder may result either from failure to consume adequate amounts of iron or from excessive consumption of dietary constituents, such as some tannins, that interfere with iron uptake. Tannins are complex substances that occur naturally in various foods and drinks derived from plants, including some vegetables, fruits, seeds, wine and tea. In the present study, rats were used as models to evaluate the effect of black tea on iron absorption. Tea reduced iron uptake from the intestinal tract when the tea was given in the same meal with iron but not when the tea was given separately. Presumably, tannin in the tea reduced iron absorption because the tannins combined with iron in the gut and formed insoluble compounds that were not readily absorbed. Because tea affected iron absorption when the tea was consumed or combined with an iron-containing meal, it is suggested that tea not be consumed when taking dietary iron supplements. Understanding factors that impair iron utilization may lead to better utilization of dietary supplements and thereby improve the nutritional health of people.
Technical Abstract: Phenolic compounds may influence iron absorption by complexing iron in the intestinal lumen or by altering intestinal permeability. We assessed the effects of tea on iron absorption and intestinal permeability in rats in two experiments. In experiment 1, rats maintained on a commercial diet were fasted overnight with free access to water and gavaged with 1.0 ml of 59Fe labeled FeCl3 (0.1 mM or 1.0 mM) and lactulose (0.5 M) in water or black tea. Iron absorption was estimated from 59Fe retention. Intestinal permeability was evaluated by lactulose excretion in the urine. Iron absorption was lower when given with tea at both iron concentrations but tea did not affect lactulose excretion. In experiment 2, rats maintained on a commercial diet were divided into two groups. One group was given black tea as the only source of water for 3 d. The other group was given water. Both groups were fasted overnight with free assess to water and then gavaged with 1.0 ml of water or black tea containing 59Fe labeled FeCl3 (0.1 mM) and lactulose (0.5 M). Iron absorption was not affected by 3 d of tea consumption but was decreased when delivered in tea. Lactulose excretion was not affected by 3 d tea consumption or by delivery in tea. These data suggest that tea affects iron absorption by forming iron complexes in the lumen.