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Kava (Piper methysticum) is a dioecious perennial shrub native to the South Pacific, where it has been used for thousands of years as the source of a narcotic sedative drink derived from its roots and used during celebrations and other events (traditional preparation involved chewing or pounding the roots to a pulp and mixing it with cold water). Since the 1990s, kava has become popular in many regions outside the South Pacific islands (including the United States, Europe, and Australia) as a relaxation and anti-anxiety agent. Studies have supported its efficacy in reducing anxiety, but concerns about safety (especially hepatotoxicity) prompted a ban by the European Union in 2002 and safety advisories from the U.S. Food & Drug Administration and other bodies.
A number of investigators have argued that the rare cases of liver damage among kava users are the result of poor quality preparations, excessive consumption, or other avoidable factors rather than safety issues intrinsic to kava consumption. Sarris et al. (2011) advised using only traditional water soluble extracts of the rhizome (root) of appropriate kava cultivars and avoiding the use of kava in combination with alcohol and possibly other psychotropic medications. They also suggested avoiding long-term use of kava until and unless the safety of such use is well established. Although most studies have failed to find a significant negative impact of kava on cognition (e.g., LaPorte et al. 2011), Sarris et al. suggested that avoiding high doses should be mandatory for anyone driving or operating heavy machinery. They called for additional investigations to assess comparative efficacy and safety (including impacts on the liver, cognition, and driving, as well as sexual effects) versus established pharmaceutical treatments. Teschke and Lebot (2011) proposed the establishment of internationally accepted quality control standards (including kavalactone composition, growing and processing methods, etc.), which they believe could allow the safe use of kava as a traditional relaxing beverage and effective anti-anxiety treatment.
Lebot and Levesque (1996) and Applequist and Lebot (2006) established that the species long known as P. wichmannii was not distinct from P. methysticum, but rather that the taxon referred to as P. methysticum represented a group of sterile cultivars selected from somatic mutants of P. wichmannii. Because the older name P. methysticum has priority, the authors suggested that the the sterile cultivars be referred to as P. methysticum var. methysticum and the wild populations as P. methysticum var. Wichmannii.
(Sarris et al. 2011 and references therein; Stacy 2011 and references therein; Teschke and Lebot 2011 and references therein)