Kava can deplete glutathione levels in the liver unfortunately. This effect is related to hepatotoxicity.
On another note, very closely know a cancer patient (not from one of my clinics), that I encouraged to take tudei (25%) mixed with a headier kava. Noble kavas from Vanuatu were tested to have flavokawain : kavalactone ratios of 0.09 on the average, whilst tudei had an average of 0.39 and wichmannii 0.38. Yet another paper tested liver toxicity in mice and found that even tudei kava had almost no hepatotoxicity normally, but when acetaminephine + kava (noble or ignoble) was added, liver toxicity was high. Flavokawain (A, B, C, and unnamed varieties) appear to be the primary antitumor components in kava, but probably not the only ones. I have spent many hours looking up research studies on this topic in the last month, specifically to help out the person I know. Some studies found better efficacy and lower toxicity using kava than two very common chemo drugs (adriamycin and doxorubicin).
In Fiji, only men tend to drink kava (except perhaps virgin girls). Men have roughly 30% the cancer rate than womn in Fiji. When Fijian men move to Australia where they have little or no kava, their prostate cancer rates go up 5.1 times. I believe the reason why women on't drink kava is not so much patriarchical, but rather since there is anecdotal evidence that it may cause miscarriages. If young women were drinking it, their populations might could have disappeared, if that is the case.