Unlike drug manufacturers, supplement producers do not have to warn about risks such as liver damage. A US study now suggests that supplements containing curcuma, green-tea extract, ashwagandha or red yeast rice may be dangerous for people with liver disease. Experts advise consulting a doctor or pharmacist before taking them. Tip: Turmeric as a spice and green tea as a drink are generally safe — but high-dose extracts can be harmful.