Table 1.

Studies reporting reductions in iron bioavailability in animal models

Reference	Subjects, n	Model	Intervention	Tannin type	Intervention length	Outcome
44	6	Rat	5, 10, 15, and 20 g tannin/kg diet vs. control	Tannic acid	3 wk	Significant linear reduction in hemoglobin (≤27%) and hepatic (≤61%) iron concentrations with tannic acid consumption.
45	9	Pig	125, 250, 500, and 1000 mg tannin/kg diet vs. control	Tannic acid	4 wk	Significant linear reduction in hemoglobin (≤21%; P = 0.028) and serum (29%, P = 0.12) iron concentrations with tannic acid consumption.
46	7	Rat	100 g tea consumption vs. 100 g tea (beverage) with various concentrations of aluminum and control	Green tea	8 wk	Significant reduction in hemoglobin (11.0 vs. 10.0 g/L; 9% reduction) and hepatic (750 vs. 250 µg/liver; 71% reduction) iron with tea consumption vs. control.
47	8	Rat	Green or black tea decoction with bean ragout meal vs. meal alone	Green or black tea	14 d	Significant depletion of hemoglobin (−1.1 and −0.95 g/L with black and green tea, respectively) and iron bioavailability (19.6% and 14.9% with black and green tea, respectively) vs. control during the study. Normal hepatic iron in tea groups vs. control (65, 89.4, and 66.3 µg/g in control, black tea, and green tea groups).
48	6	Rat	Black tea powdered diet as 25 g/kg vs. control	Black tea	12 d	Significant reduction (26%) in iron absorption vs. control, although there was a significant increase over time (24% vs. 42% at baseline and end line in tea consumers). No reduction in hepatic iron concentrations.