New clinical analysis reveals the precise biochemical mechanism by which black tea and coffee reduce iron absorption in the human body. Polyphenols—particularly those with galloyl structures—bind non-heme iron in the gastrointestinal tract, forming insoluble complexes that bypass absorption entirely. Research from the British Journal of Nutrition demonstrates black tea reduces iron uptake by 79 to 94%, with peppermint tea close behind at 84%.
The finding is especially relevant for plant-based diets and populations at risk for iron deficiency. However, the effect is reversible: adding just 50 mg of vitamin C can restore iron absorption 3 to 6-fold, effectively counteracting the polyphenol interaction. The mechanism is dose-dependent and specific to polyphenol structure, not total phenolic content, offering clinicians and patients precise strategies for optimizing micronutrient bioavailability.
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