Blumenthal emphasized that the information now coming together on kava needs
to be scientifically evaluated and addressed. And he noted this is being
done by the FDA and the trade associations and that "These considerations
and cautions represent a prudent approach to the information presently
available".
Jerry Cott, PhD., former Chief of the Psychopharmacology Research Program at
the National Institute of Mental Health said, "If the incidence of liver
toxicity for kava is correct, then according to German researchers it is
very similar to that of conventional pharmaceutical anti-anxiety and
antidepressant prescription drugs. These are generally considered to be
acceptable (though small) risks," he said, referring to the risk-benefit
comparison by which conventional medicines are evaluated.
Cott also pointed out that a small clinical study from Duke University
published in October showed no adverse effects from kava on the liver.
In 1990 the German government's Commission E, a panel of herbal experts in
the fields of medicine and pharmacy, evaluated the scientific and medical
literature and had approved the use of kava as a nonprescription medicine
for "nervous anxiety, stress, and restlessness". The safe and effective
benefits of kava to relieve symptoms of anxiety were supported last year in
a meta-analysis, a systematic statistical review of seven human clinical
trials published in the Journal of Clinical Psychopharmacology and again in
a similar critical review this year. The reviews did not find adverse
effects related to liver toxicity.
Traditionally served as a beverage in social or ceremonial ritual in island
communities of the south Pacific, kava (also known as kava kava, Piper
methysticum) has been revered as the primary herb in these cultures (e.g.,
Fiji, Vanuatu, Samoa, Tonga) for possibly two or three millennia. Kava use
in these cultures has been considered generally safe, with few adverse side
effects.
"Historically, the scientific literature does not show much basis for
concern about potential liver toxicity. These cases in Europe are
relatively recent," said Blumenthal who is also an associate professor at
the College of Pharmacy at the University of Texas at Austin.
The primary adverse effects of kava reported in the literature are
relatively minor and are usually associated with highly excessive intake.
These effects include the occasional yellowing and scaling of skin, which
returns to normal after discontinuation of the herb. Other effects
associated with high doses include slow adjustments of the eyes to changes
in light and impaired motor control (related to kava's action of relaxing
skeletal muscles, one of the reasons it is used for treating mild cases of
anxiety).
Currently, kava ranks ninth in sales of all herbal dietary supplements sold
in mainstream retail markets, with total mainstream sales in 2000 of
approximately $15 million. This statistic does not include sales in health
food stores, multi-level marketing companies, mail order, or sales by health
professionals, which could account for an additional $15 million, or
possibly more.
The American Botanical Council is the nation's leading non-profit
organization dealing with research and educational issues regarding herbs
and medicinal plants. The 13-year-old organization occupies a 2.5 acre site
in Austin, Texas where it publishes HerbalGram, a peer-reviewed journal on
herbal medicine and other educational materials for consumers and healthcare
professionals, including the highly rated The Complete German Commission E
Monographs - Therapeutic Guide for Herbal Medicines (1998). Its new
publication for health professionals, The ABC Clinical Guide to Herbs, will
be published in spring 2002. Information contact: ABC at PO Box 144345,
Austin, TX 78714-4345, ph: 512-926-4900, fx: 512-926-2345. Website:
www.herbalgram.org.