Despite promising results from in vitro experiments and rodent studies, the main drawback is the lack of large, high-quality randomized controlled trials to validate the therapeutic efficacy of TUDCA on the various conditions it is claimed to treat. While there is one large multicenter trial on primary biliary cholangitis[1] and a couple of large trials on ALS,[2] most of the clinical studies that have examined the effects of TUDCA only include a small number of participants (<30) and the effects are variable and small at best.[3][4][5][6][7]
TUDCA appears to be well tolerated in humans: side effects — primarily gastrointestinal issues like diarrhea, nausea, flatulence, and mild abdominal discomfort — are rare and mild,[1][8][9] and no major safety concerns have been identified in clinical trials. However, many clinical studies of TUDCA fail to report whether any side effects occurred. Furthermore, the exact pathways through which TUDCA exerts its effects are not fully understood (see faq:how-does-TUDCA-work). Consequently, a full understanding of TUDCA’s safety profile in humans is lacking, and the tolerable upper intake level is currently unknown. That said, the ongoing TUDCA-ALS trial includes long-term safety and tolerability as a secondary outcome, which suggests that comprehensive safety data will become available when that data is published.[10]
TUDCA has potential drug interactions. For example, some evidence has shown that TUDCA might bind to the insulin receptor, which means it could interact with drugs like insulin analogs or insulin sensitizers.[11] Furthermore, bile acid sequestrant drugs (e.g., cholestyramine, colestipol, or colesevelam) interfere with the absorption of bile acids,[12][13] which means that bile acid sequestrants could reduce the absorption of TUDCA when it is taken as a supplement. TUDCA might also interact with doxycycline, but the clinical relevance of this interaction is currently unclear.[14][15] Always consult your doctor or pharmacist before considering using TUDCA to check for drug interactions.