kava

Other Common Names: Kava kava, kava peper, awa,
yangona
Latin Name: Piper methysticum G. Forst. [Piperaceae]
Plant Part: Root



A water extract of ground kava root (actually a rhizome or underground
stem) has been used traditionally in the Pacific islands in
religious ceremonies and at social events. Modern commercial preparations
are usually made by extraction with ethanol or acetone. Pharmacological
studies have profiled the constituent kavapyrones, also
known as kavalactones, which are thought to be responsible for the
anxiety-relieving effect of kava (Schulz, Hänsel, and Tyler, 2001).
Laitan®, produced by Dr.Willmar Schwabe GmbH & Co., Karlsruhe,
Germany, contains an extract (WS 1490) prepared with acetone
and standardized to 70 percent kavalactones.
Two studies used aqueous extracts prepared by soaking either 30 g
root in 500 ml water or 200 g root in 1,000 ml water.
Kavatrol™, produced by Natrol, Inc., is sold in capsules containing
200 mg root extract including 60 mg kavalactones (30 percent)
and 50 mg dried plant material each of hops (Humulus lupulus L.)
flowers, passionflower (Passiflora incarnata L.) aerial parts (aboveground
parts), schizandra [Schisandra chinensis (Turcz.) Baill.]
fruits, and chamomile (Matricaria recutita L.) flowers.


Kava is used traditionally to make a ceremonial beverage. It has
been tested clinically most often for its use to treat anxiety. Anxiety is
a vague, unpleasant emotional state with qualities of apprehension,
dread, stress, and uneasiness. The presence and severity of characteristic
anxiety symptoms are often measured using the Hamilton Anxiety
Rating Scale (HAM-A), a standard and well-established clinician
rated scale with 14 items. The total item score is the “gold-standard”
measure used to establish and compare the efficacy of new treatments
for general anxiety disorder. Benzodiazepines are commonly used to
treat anxiety, but are associated with adverse effects such as dependence,
sedation, and memory impairment (Hardman et al., 1996).
Ten controlled trials on the use of kava were reviewed. Six studies
were conducted on anxiety. Five of these studies, which used the
product Laitan, were well-designed studies that reported significant
effects. The sixth study, which used the product Kavatrol, showed a
trend toward efficacy. The other four studies on cognitive functioning
and sleep were poorly designed, and although kava had no obvious
effect on cognitive performance, any definite conclusion would be
premature.


Anxiety

A kava product that also contains small amounts of four other botanicals,
Kavatrol, was tested for its effect on anxiety in 60 subjects.
A dose of two (200 mg) capsules were given twice daily, the equivalent
of 800 mg extract per day, or 240 mg kavalactones. Subjects evaluated
their own degree of stress in a Daily Stress Inventory and a
State-Trait Anxiety Inventory. According to the authors, the study indicated
that kava reduced the stress associated with the daily hassles
of life (Singh et al., 1998). However, our reviewers deemed the study
to be flawed due to a lack of description of the type of anxiety, coupled
with the fact that no assessment of the anxiety state was made by
a physician.



Cognitive Functioning

The effects of kava on cognitive function were tested in two poorquality
trials that used aqueous extracts of the root. The first study
compared the effects of two different doses of kava to controls who
consumed no kava in open-label experiments on 27 healthy college
students. The lower dose was an aqueous extract prepared from 30 g
root, and the second dose varied with the weight of the subject (1 g
per kg body weight, or 70 g for a 150 lb person). After a single administration,
neither kava dose altered the speed of activation of verbal
information in long-term memory or alertness (Russell, Bakker, and
Singh, 1987). The second study used a slightly higher dose of kava,
equivalent to 100 g root. In this placebo-controlled study with 24 subjects,
one dose of kava produced feelings of intoxication, body sway,
and a trend toward reduced cognitive performance (Prescott et al.,
1993).