Herbs & Supplements

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Uses

Note: In March 2002, the U.S. Food and Drug Administration (FDA) issued a warning that taking kava has been associated with rare cases of liver damage. The FDA recommends that individuals--especially those with liver diseases or those taking medications that might impair liver function--discuss the use of kava with a healthcare professional before they begin taking it.

Britain, Canada, and some European countries have prohibited the sale of all kava products due to their potentially severe side effects. In addition, kava is likely to interact with numerous other substances. Since the ban went into effect, however, some countries (such as Germany and Wales) have resumed limited sales of kava. Other countries, including the United States, are considering whether or not to take it off the market. Currently, the World Health Organization (WHO) is also re-considering the safety of kava.

In Western cultures, kava most often has been used to reduce anxiety and treat insomnia, although results of some recent clinical trials have not shown that is more effective than placebo (inactive sugar pills) for either condition. It does contain chemicals known as kava lactones (also called kava pyrones) that appear to have several calming effects on the central nervous system (CNS). However, unlike some other antianxiety and sedative drugs, the chemicals in kava do not seem to interfere with blood pressure, breathing, heart rate, or thinking.

Kava lactones may affect the amounts of certain neurotransmitters in the blood. Neurotransmitters are chemicals that carry messages from nerve cells to other cells. Taking kava may keep the body from re-absorbing one neurotransmitter known as norepinephrine. The resulting increased blood levels of norepinephrine may be associated with lessened anxiety and relaxed mood. The lactones in kava may also cause the body to produce more attachment sites for another neurotransmitter, gamma aminobutyric acid (GABA). More GABA sites may mean more GABA activity, which promotes sedation. Other ways that kava might work are to block the action of an enzyme known as monoamine oxidase-B (MAO-B) and to affect levels of a third neurotransmitter, dopamine, but in unpredictable ways. Although both MAO-B and dopamine play roles in emotional balance, the results of kava's effects on them are unclear.

Its calming effects have made kava a subject of laboratory studies for various other types of CNS conditions including attention deficit activity disorder (ADHD), depression, epilepsy, and psychoses. However, no major human studies are underway, and not enough is known about kava's activity in any of these CNS disorders to recommend its use. Presently, the FDA advises consumers that the risk of severe side effects, although very small, outweighs the possible benefits of taking kava for any reason.