“Green tea extract can cause liver injury.”

Of 1,414 liver-injury cases in the US Drug-Induced Liver Injury Network, 40 (3%) were judged to be caused by green tea products, often in multi-ingredient supplements. Most people had yellow skin or eyes, and in 3 people the injury came back after taking green tea again. One immune gene variant was found in 72% of green tea cases but only 11% of the general population, so some people seem genetically more likely to react. A US Pharmacopeia review found that reported cases involved about 140 to 1,000 mg a day of EGCG, the main catechin in extracts, and that taking extract on an empty stomach raises EGCG levels in the blood. A registry shows that the harm happens, but not how often it happens in everyone who takes an extract. Europe's food safety agency concluded in 2018 that green tea brewed the traditional way is generally safe, though rare cases of liver injury have been reported after drinking it, most likely an unusual personal reaction. The same review found that supplements giving 800 mg or more of EGCG a day raised liver enzyme levels in clinical trials.