Green Tea Interactions

Green tea catechins, especially epigallocatechin-3-gallate (EGCG), chelate non-heme iron in the gut and form insoluble complexes that reduce intestinal absorption. The effect is dose-related and most pronounced when tea is consumed with iron-containing meals or supplements.

Green tea and EGCG inhibit the proton-coupled folate transporter (PCFT) in the small intestine and inhibit dihydrofolate reductase, the enzyme that converts folic acid into its active form. In humans, concomitant green tea reduced folic acid Cmax by about 58% and AUC by about 44%.

Green tea leaves contain vitamin K, which is a cofactor for hepatic synthesis of the clotting factors that warfarin inhibits. Large or fluctuating intake of green tea can lower INR and reduce the anticoagulant effect of warfarin, as documented in a published case report.