And here is the abstract of the more recent hepatotoxcity study
The culprit of kava hepatotoxicity will continue to remain a mystery in humans, if the underlying reaction is of idiosyncratic, unpredictable, and dose-independent nature due potentially to some metabolic aberration in a few individuals emerging from kava use. In addition, kava hepatotoxicity is presently not reproducible experimentally in preclinical models, as demonstrated by studies showing whole kava extracts are not hepatotoxic. This led us to propose our 'working hypothesis' that contaminant hepatotoxins including moulds might have caused rare kava hepatotoxicity in humans. Further studies are now warranted to proof or disproof our working hypothesis, because kava hepatotoxicity possibly based on contaminant hepatotoxins could be a preventable disease. In the meantime, however, for minimizing toxicity risk in kava users, a pragmatic approach should focus on the medicinal use of an aqueous extract derived from peeled rhizomes and roots of a non-mouldy noble kava cultivar, limited to maximum 250-mg kavalactones daily for acute or intermittent use.
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Hmm. Unfortunately nothing new there -- use water extracts of roots. This one goes on to recommend only (non-moldy, seems kind of obvious really...) noble cultivars and a maximum of 250mg kavalactones at once and on a regular basis.
The theory about mold/bacterial contamination is interesting. Kava is an oily root and has to travel quite a long way to get to North America and even Europe, and one can imagine that kava farmers & shippers probably don't have rigorous food/drug safety practices in place (they get to drink it fresh, the lucky bastards). Unfortunately, it would also be the hardest to prove... I really hope nobody suffers liver damage from drinking kava ever again, but if they do I hope that somebody is able to do an analysis of the kava in question.
