There have been reports of kava induced liver toxicity, which led the EU, UK and Canada to put restrictions on kava. However, a direct link between liver toxicity and kava use seems to be extremely rare. In most cases there were other probable contributing factors, such as use of other medications, high alcohol consumption and medical conditions.  Caution should be used when taking kava. Make sure the preparation is from a company with a great reputation and derived from the root of the plant. Don't use kava if you have any liver conditions, consume alcohol frequently or are taking other medications. The safety of long term kava use hasn't been rigorously confirmed.