The safety of green tea and green tea extract consumption in adults – Results of a systematic review

Highlights

• Published toxicology and human clinical studies were reviewed, and hepatotoxicity identified as the critical effect.

• Feeding state, dosing condition and purity of catechins are key determinants of toxicity.

• GTEs closely reflecting that of traditional infusions in composition and ingestion mode are safe.

• An Observed Safe Level of 704 mg EGCG/day could be considered for GTEs consumed in beverage form.

• A safe intake level of 338 mg EGCG/day for adults could be considered for GTE ingested as a concentrated solid bolus dose.

Abstract

A systematic review of published toxicology and human intervention studies was performed to characterize potential hazards associated with consumption of green tea and its preparations. A review of toxicological evidence from laboratory studies revealed the liver as the target organ and hepatotoxicity as the critical effect, which was strongly associated with certain dosing conditions (e.g. bolus dose via gavage, fasting), and positively correlated with total catechin and epigallocatechingallate (EGCG) content. A review of adverse event (AE) data from 159 human intervention studies yielded findings consistent with toxicological evidence in that a limited range of concentrated, catechin-rich green tea preparations resulted in hepatic AEs in a dose-dependent manner when ingested in large bolus doses, but not when consumed as brewed tea or extracts in beverages or as part of food. Toxico- and pharmacokinetic evidence further suggests internal dose of catechins is a key determinant in the occurrence and severity of hepatotoxicity. A safe intake level of 338 mg EGCG/day for adults was derived from toxicological and human safety data for tea preparations ingested as a solid bolus dose. An Observed Safe Level (OSL) of 704 mg EGCG/day might be considered for tea preparations in beverage form based on human AE data.