Plate 642 Piper methysticum
The Society Islands
April and August 1769
Piper methysticum is a large-leaved shrub growing to about 2 metres and when first collected by Banks, was named Piper inebrians.
Varieties are found throughout the warmer Pacific Islands: the shrub likes warm (above 25° Celsius) shady conditions, with high rainfall and humidity and loose well-drained soils.
Kava is the Tongan name for the shrub; it is also known as Awa (Hawaii), Ava (Samoa), Yaqona (Fiji), Sakau (Pohnpei), Seka (Kosrae) and Malok (Vanuatu).
Kavakava (often quoted as another alternative name) is actually a name given to various different related shrubs (the double name suggests “false kava”) found also in New Zealand (where it is applied to Piper excelsum), and other areas too cold for the real plant to grow.
The Latin name translates roughly as “intoxicating pepper”. The shrub has psychoactive effects which are due to kavalactones, chemicals usually extracted from the roots (where the concentration is highest) which have sedative, anaesthetic and euphoriant properties.
Piper methysticum or “noble” kava cannot reproduce sexually, and produces no fruit or seed, so is propagated from stem cuttings by the growers. As a result, a number of different cultivars are found round the Pacific (often several varieties on the same island); these have slightly different habitat preferences, appearances and psychoactive effects. The varieties tend to have their own local names (so a bit like for example apple varieties).
These varieties are probably domesticated forms of either Piper wichmanii or Piper subullatum, developed in either New Guinea or Vanuatu and spread round the Pacific islands (where interestingly it probably replaced the use of Betel-nut).
The plants can be harvested from 4 years old, but are usually allowed to reach 5; this gives higher concentrations of the active substances. Kava can be supplied as a dried root, but is reputedly best used fresh; in either case the root can be chewed, but is usually pounded, with the active substances traditionally extracted with water; it can be drunk as a suspension in milk or buttermilk.
Traditional kava extract is sold for consumption on many Pacific islands, where it is felt to be less socially disruptive than alcohol; kava ‘bars’ are common. Here kava is felt to produce pleasant relaxation and mild euphoria. In much of the rest of the world it is regarded as a drug potentially of abuse, so that in the UK it is illegal to import or sell it for human consumption (though it seems to be ok to possess it, or import/sell for animal use).
Part of the problem may be that cheaper extraction methods with organic solvents produce a more toxic mix (this may be because either the method extracts other alkaloids, or is due to the organic solvents used, or probably both) with more side-effects and evidence of long-term liver damage. Recently some cheap (can be harvested after 1 year) “tudei” varieties have been introduced; again these cause more side-effects than the “noble” types such as headache and hangover and produce more (harmful) flavokavanins and less kavalactones. In Vanuatu now only organically-grown noble kava can be licensed for export.
Kava has traditional ceremonial uses in many parts of the Pacific, as a gift or to solemnise special occasions. In Hawaii the mo’i variety was felt to be so special that it was reserved for members of the royal family.
In terms of safety and medicinal use, the WHO view is that traditional use (moderate use of water-based root extract suspension) is probably safe. A Cochrane database review of existing studies suggests that kava is effective as a treatment for anxiety. As above, overuse may be associated with liver problems –especially if inferior preparations are used; there are also reports of scaly skin problems. Traditionally kava is used as an anxiolytic, an analgesic, and for gynaecological and urinary problems. Interestingly it does not seem to produce dependency or addiction.
Information from Wikipedia, Encyclopaedia Britannica, World Health Organisation, Cochrane collaboration, Natural History Museum