Black Tea Interactions

Polyphenols (tannins) in black tea bind non-heme iron in the gut lumen to form insoluble iron-tannate complexes, blocking absorption. Inhibition of non-heme iron uptake from a meal can reach 79-94% when black tea is consumed with food.

Black tea contains antithiamine factors - polyphenols such as tannins and chlorogenic acid - that oxidise thiamine (vitamin B1) into thiochrome-negative, biologically inactive forms in the gut. High habitual tea consumption has been linked to reduced thiamine status, especially in populations with marginal B1 intake.