Are kavalactones the hepatotoxic principle of kava extracts? The pitfalls of the glutathione theory.

Dear Editor: Recently, in this journal Denham et al. (2002) and (within the same paper) Whitton et al. published their ideas about the influence of glutathione in aqueous preparations respectively low alcoholic tinctures of kava (Piper methysticum roots.html) on the safety of intake regarding adverse liver reactions. Even though the theory presented is highly interesting, and deserves a closer inspection, the weak point of the argumentation is that it is based on the hypothesis that kavalactones are hepatotoxic. There is, however, currently no evidence to back up this theory. The worldwide discussion on potential liver toxicity of kava was triggered by the risk– benefit reevaluation of the German health authorities, on the assumption of hepatotoxic effects, which finally led to the ban of kava products in Germany in June 2002 (for details, see www.uni-muenster.de/Chemie/PB/Kava/ kavaroot.html). One should keep in mind, however, that the circumstances of the case reports and the existing preclinical and clinical data still do not allow a deduction of a specific hepatotoxic potential of kava extracts, even though several case reports have been cited with the evaluation of a “probable” causality in a most recent approach by Teschke (2002). However, the potentially hepatotoxic concomitant treatment of the patients was still largely left out of the discussion (Teschke, 2002). The outcome of the official German assessment was heavily criticized by experts in phytomedicine and toxicology, including the members of the German Commission E (who would normally have been consulted in the decision-making process), because the kava ban would not decrease, but rather increase the risk of potentially serious adverse effects, including liver diseases, for individual patients (Anonymous, 2002a, 2002b, 2002c). The experts of the German Commission E filed their protest against the decision in the media, however, without success.