The problem with Kava and the liver has apparently been that some forms of the supplement have included Kava plant leaves and stems (which are toxic), not just the root (which is what you want). Kava is apparently illegal in Canada.
http://en.wikipedia.org/wiki/Kava
http://www.google.com/imgres?imgurl=http://www2.ctahr.hawaii.edu/ctahr2001/CTAHRInAction/May_03/images/kawa_root.jpg&imgrefurl=http://www2.ctahr.hawaii.edu/ctahr2001/CTAHRInAction/May_03/kava.asp&h=335&w=370&sz=34&tbnid=feC4nQD-erK-MM:&tbnh=110&tbnw=122&prev=/images%3Fq%3Dkava%2Broot%2Bphoto&hl=en&usg=__hyYuMKBRekp3zwkBmrFoEEUiuYA=&ei=QtP6Sra3MsSknQeD4KWBDQ&sa=X&oi=image_result&resnum=2&ct=image&ved=0CBEQ9QEwAQ
http://www.streetdirectory.com/food_editorials/cooking/herbs_and_spices/the_kava_kava_root_side_effects_and_benefits.html