Green Tea Extract (EGCG)

Claimed to increase thermogenesis and fat oxidation, cause weight loss and reduce body fat, and act as an antioxidant and anti-cancer agent. The Cochrane review of 15 weight-loss and three weight-maintenance studies in 1,945 completing participants found, in the six studies conducted outside Japan, a mean difference of −0.04 kg (95% CI −0.5 to 0.4) — forty grams, not statistically significant. The eight Japanese studies were too dissimilar to pool and individually ranged from −0.2 kg to −3.5 kg. The geographic split is itself the finding: the only impressive numbers come from one country’s trials, which could not be combined with the rest.

There is a verified hepatotoxicity signal, demonstrated in randomised trials and acted on by two independent authorities. EFSA concluded that EGCG at or above 800 mg/day taken as a food supplement significantly raises serum transaminases relative to control, and explicitly did not set a safe supplement dose or an upper intake level — the strongest available statement that the safe margin is unknown. The USP review found the injury pattern is hepatocellular, that published case reports associate hepatotoxicity with EGCG intakes of about 140 mg up to roughly 1,000 mg/day with substantial, possibly genetic, individual variability, and that repeated bolus doses taken while fasting increase catechin bioavailability, probably by saturating first-pass elimination. It found no evidence that solvent residues, pesticide residues, pyrrolizidine alkaloids or elemental impurities were involved: the hepatotoxicity is attributable to the catechins themselves. Note that the 140 mg lower bound of reported case intakes sits far below the European Union’s 800 mg/day regulatory ceiling.

Catechins from traditionally prepared infusions, and reconstituted drinks of equivalent composition, were considered generally safe at reported intakes, with rare liver injury most likely idiosyncratic. Regulation of this compound now consists largely of warnings.