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Can green tea extract or EGCG cause liver toxicity and at what doses?
Executive Summary
Green tea extract (GTE) and its major catechin, epigallocatechin gallate (EGCG), have been linked to rare but serious liver injuries, most often in the context of high-dose supplements rather than traditional brewed tea; regulatory reviews identified increased liver enzyme elevations at or above about 800 mg EGCG per day, and case reports document acute hepatitis and, rarely, liver failure in supplement users [1] [2] [3]. The consensus of recent regulatory and clinical analyses is that traditional green tea infusions are generally safe, while concentrated extracts at high doses, prolonged use, or parenteral administration carry measurable hepatotoxic risk in susceptible individuals [1] [4].
1. Why regulators drew a line: clear evidence that high-dose EGCG raises liver enzymes
The European Food Safety Authority (EFSA) reviewed intervention trials and observational data and concluded that intakes of EGCG at or above 800 mg/day increase the likelihood of liver injury, with several randomized or controlled interventions reporting elevated ALT/AST at these doses; EFSA’s finding was echoed by the UK Committee on Toxicity in a later statement that reaffirmed 800 mg/day as a practical upper limit for supplements [1] [3]. This regulatory position rests on pooled trial data and reported transaminase elevations in nine intervention studies identified by EFSA, and it reflects a precautionary threshold rather than proof that every person exposed to 800 mg will be harmed; the evidence indicates a dose–response signal and a reproducible biomarker (ALT/AST) elevation at higher exposures, which prompted EU restrictions on commercial use of concentrated GTE in foods and supplements [5] [3].
2. Clinical reports show idiosyncratic but severe cases — supplements implicated more than brewed tea
Clinical case series and reports compiled by LiverTox and others describe acute hepatocellular injury, sometimes progressing to liver failure, in users of green tea extracts, most commonly in weight-loss or energy supplements where concentrated EGCG is present; the phenotype is typically an acute hepatitis-like syndrome with marked transaminase elevations and jaundice, and a small number of fatalities or transplant cases have been described historically [2] [6]. These reports emphasize that injuries are often idiosyncratic — unpredictable, not dose-linear for every patient, and not reproducible in animals — but they also frequently involve exposures to concentrated extracts or non-oral routes (a 2022 intravenous case report highlights the severe risk of non-oral administration), which strengthens the link between formulation/dose and harm [4] [2].
3. Context: brewed green tea behaves differently from supplements
Multiple reviews and authoritative panels emphasize that traditional green tea brewed and consumed as a beverage is generally safe, with catechin concentrations far below those used in supplements and no widespread signal of hepatotoxicity in normal consumption patterns; reported hepatotoxic cases almost universally involve supplemental, concentrated GTE preparations rather than a cup of tea [1]. EFSA explicitly distinguished between catechin exposure from traditional infusions and from supplements, finding the latter category responsible for most of the safety concerns; this distinction explains why public health guidance and regulatory actions target supplement composition and labeling, not ordinary dietary tea drinking [1].
4. Practical risk factors: dose, duration, formulation, and individual susceptibility
The documented risk factors for GTE/EGCG hepatotoxicity include high EGCG dose (≥800 mg/day), prolonged exposure (weeks to months), concentrated extract formulations, and unusual delivery routes, while underlying host factors (genetic susceptibility, concurrent hepatotoxic drugs, pre-existing liver disease) likely modulate risk in individual cases, producing idiosyncratic outcomes in some users but not others [3] [7]. Case reports of acute liver failure linked to weight-loss supplements and an intravenous preparation illustrate that both supplement formulation and route of administration can meaningfully amplify toxicity risk, and regulatory bodies have therefore focused on limiting maximum daily EGCG in consumer products and raising clinician awareness to recognize supplement-associated liver injury early [6] [4].
5. How clinicians and consumers should interpret the evidence today
Taken together, randomized studies, regulatory reviews, and case reports establish a consistent message: ordinary green tea is safe for most people, but concentrated EGCG supplements at or above roughly 800 mg/day carry a measurable risk of liver injury that has led to regulatory limits and multiple confirmed adverse-event reports; clinicians should ask about supplement use in unexplained hepatitis and consider EGCG as a possible cause, while consumers should avoid high-dose extracts, heed label warnings, and consult healthcare providers before starting supplements, especially if they have liver disease or take other hepatotoxic medicines [1] [3] [2].