A new study found high dosage, prolonged use and an inferior quality of kava contributed to the liver poisoning some people experienced in the late 90s.
Kava was banned in some countries, including Germany, after it caused liver disease in 83 people after 1998.
Professor Rolf Teschke from the Goethe University in the German city of Frankfurt has examined all German and Swiss people who suffered from liver problems after consuming kava.
Mr Teschke says there's a similar pattern in all those cases.
"The patients have taken an overdose of kava and the duration of the therapy was also prolonged. [In] 1998 there was a real kava boom, it's assumed that other kava cultivars,an inferior, toxic quality or variety, have been used."
Rolf Teschke says farmers in the Pacific must find out what they have sold prior to 1998 and farm these safe varieties.