Tauroursodeoxycholic acid is a hydrophilic bile acid found endogenously in small amounts; concentrated form of ursodiol with taurine conjugation.
Mechanism — Reduces ER stress (protein-folding stress), stabilizes mitochondrial membranes, inhibits apoptosis pathways. Direct hepatoprotective effect via bile acid pool modulation. Crosses blood-brain barrier; neuroprotective in some models.
Use case — Liver support during high-supplement-load periods, prohormone or hepatotoxic medication courses, NAFLD adjunct. Typical 250-500 mg/day, often dosed 2x.
Caveats — Diarrhea at higher doses. Don't combine carelessly with bile-acid sequestrants. Pricier than milk thistle but with cleaner mechanism.