A remedy peppered with variety of problems

The Irish Times
Health Supplement, p. 13
11 November 2008

DOES IT WORK? Does Kava help treat anxiety? 

KAVA IS a popular social drink in the South Pacific islands. Captain James Cook led the first European expedition to report on the drink, calling it “intoxicating pepper”.

A water-soluble extract was prepared as part of an elaborate ritual and the drink played a similar role to alcohol in our society. Today, kava herbal remedies are made using alcohol or acetone to make an extract from the same pepper plant.

The different methods of preparation are one of the reasons proposed to explain why kava has recently led to rare, but serious, adverse effects in some people. More than 100 cases of serious liver toxicity, a few fatal, have been reported after people took kava herbal remedies. For this reason, kava products were voluntarily taken off the market in Ireland in 2002. The UK, Germany, Switzerland and Canada have banned their sale. However, kava products remain on the market in the US and Australia and on the internet, and cases of liver toxicity continue to be reported.

Problematic aspects

The ban on kava sales has had a detrimental effect on the economies of the South Pacific islands which exported kava. During the 1990s, the market for kava increased massively as its reputation for treating anxiety spread to Western countries. However, the pepper plant from which it is made is slow-growing. The extract is traditionally made from the roots when the plant is four or five years old. Pressure to keep up with demand is believed to have led to cultivation of faster- growing varieties which contained a different mixture of compounds. In addition, stems and leaves began to be used in making the remedies. Research has since revealed that these contain toxic compounds not found in the roots.

The problems are not just due to the plant material. One of the anomalies with kava is that some people can take the remedy without any problems while others have adverse reactions almost immediately. Research is now showing that about 10 per cent of people with European ancestry have a genetic trait which is not found in Pacific Islanders. People with this trait are “poor metabolisers” which allow liver toxins to build up and cause damage. Such people are also at higher risk of side effects when taking kava along with other prescription medicines which are metabolised the same way.

Evidence from studies

Ironically, there is evidence that when people do not have adverse liver problems, kava is effective in relieving mild generalised anxiety disorder (but not other forms of anxiety). One particular German product, WS1490, has been shown to be more effective than placebo and as effective as mild valium-like prescription medicines. It is standardised to contain a fixed per cent of active ingredients, but other products vary widely in their strength. Some of the studies conducted with kava products have found them to be no more effective than a placebo.


The voluntary removal of kava products from the Irish market is in keeping with other international regulatory agencies which have banned the sale of kava products. A review in 2007 by the UK Medicines and Healthcare Products Regulatory Agency concluded that the ban should continue in the interests of public health.

Anyone using kava anyway should be particularly alert for signs of liver toxicity, which can include yellow skin (jaundice), fatigue and dark urine. These can develop within a few weeks of taking kava. Kava should not be taken for more than a month without seeking medical advice. Liver function tests can be ordered by a GP to verify whether any problems are developing. Taking alcohol along with kava can hasten liver toxicity. Anyone taking prescription medicines, especially for anxiety, should not take kava.

One final warning is needed. Kava is traditionally used as a social beverage which induces relaxation and drowsiness. This can affect reaction times and lead to poor judgments, requiring particular caution when driving or operating machinery.

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