EGCG

How strong is the research?

2 papers read, 2 supporting.

Tested as: green tea catechin extracts/supplements as used across pooled RCTs (typically higher-dose extract forms rather than brewed tea alone)

Before you take it

• EFSA (2018) Scientific Opinion found that EGCG doses ≥800 mg/day from food supplements produce statistically significant increases in serum transaminases; EU Regulation 2022/2340 restricts single-portion EGCG content to <800 mg. No NIH/IOM Tolerable Upper Intake Level (UL) has been established for EGCG as a supplement; EFSA's 800 mg/day threshold is the most specific regulatory benchmark available.
• Drug-induced liver injury (DILI): EFSA reviewed 78+ case reports of liver injury linked to green tea extract supplements; risk is elevated with fasted intake and at high doses. UK Committee on Toxicity (COT) has independently reviewed and corroborated this evidence.
• CYP3A4 and P-glycoprotein inhibition: EGCG may elevate plasma concentrations of statins (atorvastatin, simvastatin), calcineurin inhibitors (cyclosporine, tacrolimus), and some calcium channel blockers.
• Non-heme iron absorption inhibition: EGCG significantly reduces non-heme iron absorption; caution is warranted in iron-deficient individuals and those with anemia.
• Antibiotic interaction: EGCG chelates fluoroquinolones and may reduce beta-lactam and tetracycline absorption; doses should be separated by at least 2h before or 4-6h after antibiotic administration per NIH ODS guidance.
• Mild antiplatelet activity: additive bleeding risk with warfarin or direct oral anticoagulants (DOACs).
• Contraindicated at supplemental doses during pregnancy: high-dose EGCG inhibits dihydrofolate reductase, impairing folate metabolism.
• Variable caffeine content: many green tea extracts retain caffeine; may exacerbate anxiety, hypertension, or arrhythmia in sensitive individuals.