I might be late to the game on this, but apparently green tea extract, specifically EGCG has been linked to liver damage. Granted, it’s only a correlation, not necessarily causation. I took 1g per day for 3 months during my competition shred. My blood work ALT and AST were normal during this time, but I’m not going to take chances with it next time.
Green tea extracts are widely used without problems. For me , it seems one of 2 possibilities:
Some people are genetically more (a lot more) affected in a way that damages the liver.
Heavy metal contamination. Green tea might contain quite dangerous levels if sourced from cheapest place.