Table 2.

Studies reporting no or inconsistent reductions in iron bioavailability or iron status in animal models¹

Reference	Subjects, n	Model	Intervention	Tannin type	Intervention length	Outcome
49	6	Rat	Control vs. various types of tea in food	Black tea	16 d	No significant differences in iron absorption or hepatic iron vs. control.
38	6	Rat	Green tea diet or gavage vs. control	Green tea	30 d	No significant differences in iron absorption (3.7% vs. 5.6% over time and 43% vs. 63% in control vs. tea, respectively; P = 0.292) or hepatic iron (60.9 vs. 54.2 µg Fe/g liver, control vs. tea, respectively; P = 0.521) vs. control.
50	10	Rat	Meal with phytoferritin vs. condensed tannins (PA) and phytoferritin	Condensed tannins	4 wk	Significant reduction in hemoglobin (11.9 vs. 10.0 g/L, respectively) and serum iron (10.33 vs. 21.43 µmol/L, respectively) for control vs. proanthocyanidins. Iron repletion and ferritin (23.4 vs. 20.98 ng/mL, respectively) not significantly different from no-proanthocyanidin group.
51	7	Rat	Meals consisting of casein, soy, chickpea, or red kidney bean flour	Condensed tannins	1 wk	No significant differences in iron retained, total hemoglobin in rats consuming meals containing various amounts of polyphenols vs. control; no differences in iron retention between high- and low-tannin kidney bean meals.
52	16	Pig	Grape meal– and hops-based diets vs. control	Condensed tannins	4 wk	No significant differences in iron, TIBC, transferrin, hepatic iron, and fecal iron between groups.
36	8	Pig	Red- vs. white-bean meals	Condensed tannins	4 wk	No significant difference in hemoglobin/hemoglobin repletion efficiency in white and red beans (26% vs. 30%, respectively).

¹PA, proanthocyanidins; TIBC, total iron binding capacity.