Kava on the brain
I recently drank some of the interesting root-based drink kava on the Pacific island of Vanuatu. I鈥檓 happy to report that it had some odd effects. What exactly did it do to my brain?
鈥� Because your correspondent drank the kava in Vanuatu, it may have been made using either fresh or dried roots, while in other countries where kava is drunk 鈥� namely, Fiji, Tonga and Samoa 鈥� it is almost exclusively prepared from dried roots. Vanuatu kava, especially that from fresh material, is much more potent and its effects tend to be greater.
The active chemical ingredients in kava, called kavalactones, produce a number of effects in both the brain and the rest of the body. Initially the tongue becomes numb, as does the inner lining of the mouth. Some of the other effects may depend on the familiarity of the user with the drink. A novice user may find the drink bitter or sour and that food loses its taste and flavour. Nausea may follow, along with headache and intestinal discomfort, effects not experienced by the habitual drinker.
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In contrast to alcohol, kava used in moderate amounts produces a calming effect, reduces fatigue, allays anxiety and stress, and induces a generally pleasant, cheerful and sociable attitude. It is partly for these reasons that it has been consumed in South Pacific communities for hundreds of years as a social drink. One hears expressions like, 鈥測ou cannot hate with kava in you鈥� and 鈥渦nlike liquor, kava does not provoke aggressive, boisterous or violent behaviour鈥�. Nor does it cause the hangovers, physical addiction, memory loss or diminished reasoning associated with alcohol.
Kavalactones have been shown to produce a number of biological effects in the brain that could account for the above observations. They include the compounds鈥� ability to produce a local anaesthetic-like effect 鈥� hence the numbing of the tongue 鈥� and to act on drug receptors in a similar way to some anxiety and stress medications such as benzodiazepine. As a result, kava was introduced in the western world to treat anxiety, stress, restlessness and sleep disorders.
However, less positive effects have been reported with the use of excessive amounts of kava, and in a few cases where it has been combined with medical drugs.
There have been some reports of kava causing liver damage in people who live in western nations where it has been used in the form of pills and other such preparations. Consequently, some countries have suspended the sale of kava or issued health advisories. As this medical condition has not been reported in traditional kava drinkers, it is unclear whether it is directly associated with kava itself, or with the manufacturing process or some other factors. In any case, kava is still widely drunk by people from the South Pacific, including myself 鈥� I am originally from Fiji.
For further information on the effects of kava, please consult my article in CNS Drugs (vol 16, p 731), published in 2002, which is also available directly from yadhu_singh@sdstate.edu.
Yadhu Singh
Brookings, South Dakota, US
鈥� Exactly how kava acts on the brain is unknown. Benzodiazepine anti-anxiety drugs work by stimulating the brain鈥檚 gamma-aminobutyric acid (GABA) receptor proteins, which regulate signal transmission between nerve cells, but kava is not thought to work on GABA and is also thought to act in a different way to the opioid drugs. It may work on the brain鈥檚 limbic system, located in the medial temporal lobe of the brain, which is involved in controlling emotions. There has been speculation that it may antagonise the neurotransmitter chemical dopamine.
Jamie Horder
Oxford, UK
Boring method
In the 1 March edition of 鈥淭he Last Word鈥�, Syd Curtis asks a question about how to make ice, saying he got the recipe from The Windsor Recipe Book. In passing, he also mentioned the book had a recipe for 鈥渉ow to bore holes in glass using camphor dissolved in turpentine鈥�. Does this method really work, and if so, what are the details?
鈥� It is the drill which makes the hole, not the turpentine and camphor. I used this method successfully about 50 years ago. It is essential to frequently release the pressure on the drill and flood more turpentine and camphor onto the area of contact between drill and glass, otherwise a hot spot will form and shatter the glass. I believe that the principal function of the turpentine and camphor is as a coolant.
L. Williams
Birmingham, UK
鈥� Diamond used to be the only really effective material for drilling glass, but the high cost drove glass workers to use alternatives such as hardened steel drills. They used many personal tricks to help them, but success ultimately depended on the skill of the artisan. Recipes for making glass used to be less reliable and more variable, often giving products that were heat-sensitive and likely to shatter. Drilling through dry, thick glass was almost bound to cause local heating and start a crack. Covering the working surface with water improved things, though skill and patience were still required.
Other fluids, particularly solutions of camphor in turpentine or white spirit, were popular because they did not corrode metal tools as strongly as water, were more mobile than water, and they wet the surface more rapidly. This is important, because a fluid that wets the surface of splitting glass helps to reduce the likelihood of the crack propagating further. Wet glass also cools more rapidly, and the fluids reduce friction. The tool can then break off microscopic crumbs of glass, much as a razor can slide harmlessly over lubricated skin to remove stubble.
Jon Richfield
Somerset West, South Africa
This week鈥檚 questions
Breaking the mould
Sometimes our cheddar cheese develops a bluish-green circular mould. My wife maintains the cheese is safe to eat, especially if you cut the mould off. I say you shouldn鈥檛 eat it. Which one of us is correct and why?
Gary Pearson
Birmingham, UK
Canine comforts
Dogs often greet people by jumping up and licking their faces. Why?
K. Kessler
Letchworth, Hertfordshire, UK