|Piper methysticum leaves|
The roots of the plant are used to produce a drink with sedative, anesthetic, euphoriant, and entheogenic properties. Kava is consumed throughout the Pacific Ocean cultures of Polynesia, including Hawaii, Vanuatu, Melanesia and some parts of Micronesia. (See canoe plants.) Kava is sedating and is primarily consumed to relax without disrupting mental clarity. Its active ingredients are called kavalactones. A systematic review of its evidence by Cochrane concluded it was likely to be more effective than placebo at treating short-term social anxiety.
- 1 Characteristics
- 2 Pharmacology
- 3 Preparation and consumption
- 4 Effects of consumption
- 5 Regulation
- 6 See also
- 7 References
- 8 Literature
- 9 External links
The several cultivars of kava vary in concentrations of primary and secondary psychoactive alkaloids. The largest number are grown in the Republic of Vanuatu, and so it is recognised as the "home" of kava. Kava was historically grown only in the Pacific islands of Hawaii, Federated States of Micronesia, Vanuatu, Fiji, the Samoas and Tonga. Some is grown in the Solomon Islands since World War II, but most is imported. Kava is a cash crop in Vanuatu and Fiji.
The kava shrub thrives in loose, well-drained soils where plenty of air reaches the roots. It grows naturally where rainfall is plentiful (over 2,000 mm/yr). Ideal growing conditions are 70–95 °F (21–35 °C) and 70–100% relative humidity. Too much sunlight is harmful, especially in early growth, so kava is an understory crop.
Kava cannot reproduce sexually. Female flowers are especially rare and do not produce fruit even when hand-pollinated. Its cultivation is entirely by propagation from stem cuttings.
Traditionally, plants are harvested around four years of age, as older plants have higher concentrations of kavalactones. After reaching about 2 m height, plants grow a wider stalk and additional stalks, but not much taller. The roots can reach a depth of 60 cm.
Kava consists of sterile cultivars cloned from its wild ancestor, Piper wichmanii. Today it comprises hundreds of different cultivars grown across the Pacific. Each cultivar has not only different requirements for successful cultivation, but also displays unique characteristics both in terms of its appearance, and in terms of its medicinal and psychoactive properties.
Noble and Non-Noble Kava
Scholars make a distinction between the so-called "noble" and non-noble kava. The latter category comprises the so-called "tudei" (or "two-day") kavas, medicinal kavas and wild kava (Piper wichmanii, the ancestor of domesticated Piper methysticum). Traditionally, only noble kavas have been used for regular consumption due to their more favourable composition of kavalactones and other compounds that produces significantly more pleasant effects and has much lower potential for causing such negative side-effects as nausea or "kava hangover". The noble cultivars are in fact a result of centuries of conscious selection of mutations with the most desirable properties: growers have selected cultivars to improve the chemical composition responsible for the physiological effects.
According to Dr Vincent Lebot, the far more pleasant and beneficial effects of noble cultivars explain the fact that only these cultivars were spread around the Pacific by Polynesian and Melanesian migrants with presence of non-noble cultivars limited to the islands of Vanuatu from which they originate. More recently, it has been suggested that the widespread use of tudei cultivars in the manufacturing of several kava products might have been the key factor contributing to the rare reports of adverse reactions to kava observed among the consumers of kava-based pharmaceutical products in Europe. This could explain why no significant adverse health effects are observed among kava drinkers in the South Pacific who very rarely, if ever, consume non-noble varieties, especially in countries that generally do not grow any tudei cultivars (i.e. Tonga, Samoa and French Polynesia).
Tudei varieties have traditionally not been grown in Hawaii and Fiji, but in recent years there have been reports of farmers attempting to grow "isa" or "palisi" non-noble cultivars in Hawaii and of imports of dried tudei kava into Fiji for further re-exporting. The key reason why many farmers and distributors are interested in growing and selling tudei varieties is the fact that they appear to be significantly easier and cheaper to grow (while it takes up to 5 years for noble kava to mature, non-noble varieties can often be harvested just one year after being planted). Another factor that has allowed the spread of non-noble varieties is the fact that while traditional drinkers would immediately be able to detect the unpleasant characteristics of tudei, many new consumers from outside of the South Pacific lack any knowledge about kava and hence can be persuaded that tudei-based products offer a normal kava experience.
The concerns about the adverse effects of non-noble varieties produced by their undesirable composition of kavalactones and high concentrations of potentially harmful compounds not present in any significant concentration in the noble varieties, have led to the creation of legislation that prohibits their exports from such countries as Vanuatu. Likewise, efforts have been made to educate the non-traditional customers about the difference between noble and non-noble varieties and that non-noble varieties do not offer the same benefits as noble ones and can potentially cause adverse reactions. In recent years, government institutions and non-profit NGOs (such as the US-based True Kava Group Labs) have been set up with the aim of monitoring kava quality, producing regular reports, certifying vendors selling proper, noble kava and warning customers against products that may contain tudei varieties.
Kava growing regions
In Vanuatu, exportation of kava is strictly regulated. Only strains they deem as "noble" varieties that are not too weak or too potent are allowed to be exported. Only the most desirable strains for everyday drinking are selected to be noble varieties to maintain quality control. In addition, their laws mandate that exported kava must be at least five years old and farmed organically. Their most popular noble strains are "Boroguu" or "Boronggoru" from Pentecost Island, "Melomelo" from Aoba Island (called sese in north Pentecost Island), and "Palarasul" kava from Espiritu Santo. In Vanuatu, Tudei ("two days") kava is reserved for special ceremonial occasions and exporting it is not allowed. "Palisi" is a popular Tudei variety.
In Hawaii, there are many other strains of kava (Hawaiian: ʻawa). Some of the most popular strains are the Mahakea, Moʻi, Hiwa and Nene varieties. The Aliʻi (kings) of precolonial Hawaii coveted the Moʻi variety, which had a strong cerebral effect due to a predominant amount of the kavalactone kavain. This sacred variety was so important to them that no one but royalty could ever experience it, "lest they suffer an untimely death". The reverence for Hiwa in old Hawaiʻi is evident in this portion of a chant recorded by Nathaniel Bright Emerson and quoted by E. S. Craighill and Elizabeth Green Handy. "This refers to the cup of sacramental ʻawa brewed from the strong, black ʻawa root (ʻawa hiwa) which was drunk sacramentally by the kumu hula":
- The day of revealing shall see what it sees:
- A seeing of facts, a sifting of rumors,
- An insight won by the black sacred ʻawa,
- A vision like that of a sacred god!
Winter describes a hula prayer for inspiration which contains the line, He ʻike pū ʻawa hiwa. Pukui and Elbert translated this as "a knowledge from kava offerings". Winter explains that ʻawa, especially of the Hiwa variety, was offered to hula deities in return for knowledge and inspiration.
Relationship with Kawakawa
Kawakawa (Piper excelsum) plant, known also as "Maori kava" is often confused with kava. While the two plants look similar and have similar names, they are different, albeit related, species. Kawakawa is a small tree endemic to New Zealand, which is of crucial importance to traditional, indigenous Māori culture and medicine. It is most likely not a coincidence that this plant has a similar name to kava (piper methysticum). As noted by the Kava Society of New Zealand "in all likelihood the kava plant was known to the first settlers of Aotearoa [New Zealand]. It is also possible that (just like the Polynesian migrants that settled in Hawaii) the Maori explorers brought some kava with them. Unfortunately, most of New Zealand is simply too cold for growing kava and hence the Maori settlers lost their connection to the sacred plant." According to Lebot et al. (1997) "In New Zealand, where the climate is too cold for kava, the Maori gave the name kawa-kawa to another Piperaceae, M. excelsum, in memory of the kava plants they undoubtedly brought with them and unsuccessfully attempted to cultivate. The Maori word kawa also means "ceremonial protocol", recalling the stylized consumption of the drug typical of Polynesian societies". Kawakawa doesn't have any of kava's relaxing psychoactive properties. It is however commonly used in Maori medicine for the treatment of skin infections, wounds and cuts, and (when prepared as a tea) for stomach upsets and other conditions.
Fresh kava root contains on average 80% water. Dried root contains approximately 43% starch, 20% dietary fiber, 15% kavalactones, 12% water, 3.2% sugars, 3.6% protein, and 3.2% minerals. Kavalactone content is greatest in the roots and decreases higher up the plant. Relative concentrations of 15%, 10% and 5% have been observed in the root, stump, and basal stems, respectively.
The mature roots of the kava plant are harvested after a minimum of four years (at least five years ideally) for peak kavalactone content. Most kava plants produce around 50 kg (110 lb) of root when they are harvested. Kava root is classified into two categories: crown root (or chips) and lateral root. Crown roots are the large-diameter pieces that look like (1.5 to 5 inches (38 to 127 mm) diameter) wooden poker chips. Most kava plants consist of approximately 80% crown root upon harvesting. Lateral roots are smaller-diameter roots that look more like a typical root. A mature kava plant is about 20% lateral roots. Kava lateral roots have the highest content of kavalactones in the kava plant. "Waka" grade kava is made of lateral roots only.
A total of 18 different kavalactones (or kavapyrones) have been identified to date, at least 15 of which are active. However, six of them, including kavain, dihydrokavain, methysticin, dihydromethysticin, yangonin, and desmethoxyyangonin, have been determined to be responsible for about 96% of the plant's pharmacological activity. Some minor constituents, including three chalcones, flavokavain A, flavokavain B, and flavokavain C, have also been identified, as well as a toxic alkaloid, pipermethystine.
- Potentiation of GABAA receptor activity (by kavain, dihydrokavain, methysticin, dihydromethysticin, and yangonin).
- Inhibition of the reuptake of norepinephrine (by kavain and methysticin) and possibly also of dopamine (by kavain and desmethoxyyangonin).
- Agonism of the CB1 receptor (by yangonin).
- Inhibition of voltage-gated sodium channels and voltage-gated calcium channels (by kavain and methysticin).
- Monoamine oxidase B reversible inhibition (by all six of the major kavalactones).
Receptor binding assays with botanical extracts have revealed direct interactions of leaf extracts of kava (which appear to be more active than root extracts) with the GABA (i.e., main) binding site of the GABAA receptor, the D2 receptor, the μ- and δ-opioid receptors, and the H1 and H2 receptors. Weak interaction with the 5-HT6 and 5-HT7 receptors and the benzodiazepine site of the GABAA receptor was also observed.
Potentiation of GABAA receptor activity may underlie the anxiolytic effects of kava, while elevation of dopamine levels in the nucleus accumbens likely underlie the moderately psychotropic effects the plant can produce. Changes in the activity of 5-HT neurons could explain the sleep-inducing action  However, failure of the GABAA receptor inhibitor flumazenil to reverse the anxiolytic effects of kava in mice suggests that benzodiazepine-like effects are not contributing to the pharmacological profile of kava extracts.
Recent usage of kava has been documented in forensic investigations by quantitation of kavain in blood specimens. The principal urinary metabolite, conjugated 4'-OH-kavain, is generally detectable for up to 48 hours.
Preparation and consumption
Kava is consumed in various ways throughout the Pacific Ocean cultures of Polynesia, Vanuatu, Melanesia and some parts of Micronesia and Australia. Traditionally, it is prepared by either chewing, grinding or pounding the roots of the kava plant. Grinding is done by hand against a cone-shaped block of dead coral; the hand forms a mortar and the coral a pestle. The ground root/bark is combined with only a little water, as the fresh root releases moisture during grinding. Pounding is done in a large stone with a small log. The product is then added to cold water and consumed as quickly as possible.
The extract is an emulsion of kavalactone droplets in starch and buttermilk. The taste is slightly pungent, while the distinctive aroma depends on whether it was prepared from dry or fresh plant, and on the variety. The colour is grey to tan to opaque greenish.
Kava prepared as described above is much more potent than processed kava. Chewing produces the strongest effect because it produces the finest particles. Fresh, undried kava produces a stronger beverage than dry kava. The strength also depends on the species and techniques of cultivation. Many find mixing powdered kava with hot water makes the drink stronger.
In Vanuatu, a strong kava drink is normally followed by a hot meal or tea. The meal traditionally follows some time after the drink so the psychoactives are absorbed into the bloodstream quicker. Traditionally, no flavoring is added.
In Papua New Guinea, the locals in Madang province refer to their kava as waild koniak ("wild cognac" in English).
Fijians commonly share a drink called grog made by pounding sun-dried kava root into a fine powder, straining and mixing it with cold water. Traditionally, grog is drunk from the shorn half-shell of a coconut, called a bilo. Grog is very popular in Fiji, especially among young men, and often brings people together for storytelling and socializing. Drinking grog for a few hours brings a numbing and relaxing effect to the drinker; grog also numbs the tongue and grog drinking typically is followed by a "chaser" or sweet or spicy snack to follow a bilo.
Supplements and pharmaceutical preparations
Pharmaceutical and herbal supplement companies extract kavalactones from the kava plant using solvents such as supercritical carbon dioxide, acetone and ethanol to produce pills standardized with between 30% and 90% kavalactones. Many experts warn against using such extracts due to the unknown quantities and compositions of compounds extracted using these methods, as well as the difficulty of determining the quality of the plant material used in their manufacturing and instead recommend using traditional kava products (i.e. water extractions of dried or fresh noble roots).
Kava is used for medicinal, religious, political, cultural and social purposes throughout the Pacific. These cultures have a great respect for the plant and place a high importance on it. In Fiji, for example, a formal yaqona (kava) ceremony will often accompany important social, political, religious, etc. functions, usually involving a ritual presentation of the bundled roots as a sevusevu (gift), and drinking of the yaqona itself.
With kava's increasing popularity, bars serving the plant in its liquid state are beginning to open up outside of the South Pacific. Starting in the early 2000's, kava bars first opened within the beach communities of Florida, Hawaii, and California. Since then, locations have spread to other regions. While some bars have been committed to only serving the traditional forms and types of kava, other establishments have been accused of serving non-traditionally consumed non-noble kava varieties (cheaper to obtain, but with a much higher potential for producing unpleasant effects and adverse reactions than noble kava varieties) or serving kava with other substances, including alcohol.
Effects of consumption
The nature of effects will largely depend on the strain of the kava plant and the form of its consumption. Traditionally only noble kava cultivars have been consumed as they are widely known not only as safe but also for their very pleasant physiological effects, potential medicinal properties and low risk of any adverse reactions The specific effects of various noble kava depend on a number of factor such as the cultivar used (and the related specific composition of kavalactones), age of the plant and the form of its consumption. However, it can be stated that in general noble kava produces a state of calmness, relaxation and well-being without diminishing cognitive performance or influencing drinker's capacity to think clearly; with an initial talkative period, followed by muscle relaxation and eventual sleepiness.
According to one contemporary description:
Kava seizes one’s mind. This is not a literal seizure, but something does change in the processes by which information enters, is retrieved, or leads to actions as a result. Thinking is certainly affected by the kava experience, but not in the same ways as are found from caffeine, nicotine, alcohol, or marijuana. I would personally characterize the changes I experienced as going from lineal processing of information to a greater sense of “being” and contentment with being. Memory seemed to be enhanced, whereas restriction of data inputs was strongly desired, especially with regard to disturbances of light, movements, noise and so on. Peace and quiet were very important to maintain the inner sense of serenity. My senses seemed to be unusually sharpened, so that even whispers seemed to be loud while loud noises were extremely unpleasant.
Despite its psychoactive effects, kava is not considered to be physically addictive and its use does not lead to dependency.
Kava has been the key plant of the traditional medicine of the islands of the South Pacific for centuries. It has been used for a wide range of both Central Nervous System (CNS)-centered and peripheral effects. While the former group of effects, most notably kava's potential for treating or managing anxiety, stress and depression, have received the most scientific and popular attention, much of the broad list of traditional medicinal uses is related to its peripheral effects. As noted in one literature review: "Peripherally, [kava] is indicated in traditional Pacific medicine for urogenital conditions (gonorrhea infections, chronic cystitis, difficulty urinating), reproductive and women's health (...), gastrointestinal upsets, respiratory ailments (asthma, coughs, and tuberculosis), skin diseases and topical wounds, and as an analgesic, with significant subtlety and nuance attending the precise strain, plant component (leaf, stem, root, etc.) and preparative method to be used."
Kava today is primarily known for its anxiolytic properties. According to one comprehensive review of literature and research findings: "The current weight of evidence supports the use of kava in treatment of anxiety with a significant result occurring in four out of six studies reviewed." 
According to numerous studies, including the recent placebo-controlled clinical trial undertaken at the University of Melbourne kava could be a safe, non-addictive and effective remedy in treating generalized anxiety disorder(GAD) and a potentially safer and alternative to tricyclic antidepressants and benzodiazepines for the treatment of anxiety disorders.
Toxicity and safety
In 2001, concerns were raised about the safety of kava, which led to restrictions and regulations in several countries, as well as reports by the United States CDC  and FDA. Most of the concerns were related to a small number of reports indicating potential cases of hepatotoxicity caused by consumption of various commercial products derived from kava. A number of scientists and medical practitioners criticized the poor quality of the reports by pointing out that most of the reported rare cases of hepatotoxicity involved patients with a history of alcohol or prescription drugs abuse or concomitant use of medicines known as potentially hepatotoxic. In light of the research findings, on June 10, 2014, the German Administrative Court overturned the 2002 ban reinstating the regulatory requirements of 2001. The court stated that risk from kava exposure had not been clearly demonstrated, nor does it appear unusually high, an opinion presumably driven by the very small number of cases of reported toxicity (n ~ 3) with even a certain degree of causality linked to kava in a global kava-consuming community that may number in the millions of doses consumed daily.
According to a comprehensive review of the relevant literature by Showman et al. (2014): "Despite the link to kava and liver toxicity demonstrated in vivo and in vitro, in the history of Western kava use, toxicity is still considered relatively rare. Only a fraction of the handful of cases reviewed for liver toxicity could be, with any certainty, linked to kava consumption and most of those involved the co-ingestion of other medications/supplements. That means that the incident rate of liver toxicity due to kava is one in 60-125 million patients." According to an in-depth human health risk assessment commissioned by the New Zealand and Australian governments, while consumption of kava may result in such minor and reversible side effects as kava dermopathy (see below), "there is no evidence that occasional use of kava beverage is associated with any long-term adverse effects, including effects on the liver."
Recent publications also confirm that kava appears to be safe and that the previously reported extremely rare cases of hepatotoxicity were in most cases likely related to rare idiosyncratic allergic reactions. The only remaining area of potential concern is the use of the so-called "two-day" (known also as "tudei", "isa", "palisi") and wild (piper wichmanii) cultivars (traditionally not consumed) in the manufacturing of kava-based pharmaceutical products due to their very different phytochemistry and relatively high concentrations of potentially harmful compounds (flavokavains). While other ("noble") cultivars also contain these compounds "toxicity seems to be triggered only at relatively high concentrations, too high to be of relevance with the use of noble kava or its corresponding extract preparations". In line with these findings, consumption of "two day" varieties is not recommended. Such cultivars mainly grow in Vanuatu which outlawed their exports in 2004.
Several adverse interactions with drugs have been documented, both prescription and nonprescription – including, but not limited to, anticonvulsants, alcohol, anxiolytics (CNS depressants such as benzodiazepines), antipsychotics, levodopa, diuretics, and drugs metabolized by CYP450 in the liver.
A few notable potential drug interactions are, but are not limited to:
- It has been reported that combined use of alcohol and kava extract can have additive sedative effects in mice. However, this additive effect has not been studied in humans. But separately kava has been shown to induce sedation. Regarding cognitive function, kava has been shown to have additive cognitive impairments while taken with alcohol when compared to taking placebo and alcohol alone.
- Anxiolytics (CNS depressants such as benzodiazepines and barbiturates)
- Dopamine Agonist - Levodopa
- One of levodopa’s chronic side effects that Parkinson’s patients experience is the "on-off phenomenon" of motor fluctuations where there will be periods of oscillations between "on" where the patient experiences symptomatic relief and "off" where the therapeutic effect wears off early. When taking levodopa and kava together it has been shown that there is an increased frequency of this "on-off phenomenon".
The Australian studies from the late 1990s that contributed towards the rise of concerns about kava focused on populations with heavy concomitant consumption of alcohol and overall poor health. In these studies, heavy kava use in an Aboriginal community in Arnhem Land was associated with overall poor health, a puffy face, scaly rash, and a slight increase in patellar reflexes. A 2012 analysis of cases worldwide proposed that mold could have also contributed to the very rare cases hepatotoxicity induced by kava-based pharmaceutical products.
Long term and heavy kava consumption is associated with a fully reversible skin condition known as "kava dermopathy" or kani kani (in Fiji) characterised by dry and scaly skin covering the palms of the hands, soles of the feet, and back. Despite numerous studies, the mechanism that causes kava dermopathy is poorly understood "but may relate to interference with cholesterol metabolism". The condition is easily treatable with abstinence or lowering of kava intake as the skin appears to be returning to its normal state within a couple of weeks of reduced or no kava use.
Kava remains legal and regulated as food or dietary supplement in most countries. Several Pacific island-states have created specific legislation aimed at regulating the quality of their kava exports or preventing the exports or consumption of non-noble kava varieties or the parts of the plant that are unsuitable for consumption (leaves, stems). Some countries (such as New Zealand) have issued regulations prohibiting the sale of impure kava products (i.e. containing the above-the ground parts of the plant) and non-water based kava extracts (due to the inability of determining the quality of the plant material used in their manufacturing).
Following the discussions on the safety of certain pharmaceutical products derived from kava and sold in Germany, in 2002 the EU imposed a temporary ban on imports of kava-based pharmaceutical products. The sale of kava plant became regulated in Switzerland, France, and the Netherlands. Some Pacific Island States who had been benefiting from the export of kava to the pharmaceutical companies have attempted to overturn the EU ban on kava-based pharmaceutical products by invoking international trade agreements at the WTO: Fiji, Samoa, Tonga and Vanuatu argued that the ban was imposed with insufficient evidence. The pressure prompted Germany to reconsider the evidence base for banning kava-based pharmaceutical products. On June 10, 2014, the German Administrative Court overturned the 2002 ban making selling kava as a medicine legal (personal possession of kava has never been illegal), albeit strictly regulated. In Germany, Kava-based pharmaceutical preparations are currently prescription drugs. Furthermore, patient and professional information brochures have been redesigned to warn about potential side effects. These strict measures have been opposed by some of the leading kava scientists. In early 2016 a court case has been filed against the Bundesinstitut für Arzneimittel und Medizinprodukte (BfArM/German Federal Institute for Drugs and Medical Devices) arguing that the new regulatory regime is too strict and not justified.
Poland is the only EU country with an "outright ban on kava" and where the mere possession of kava is prohibited and may result in a prison sentence.
In the United Kingdom it is a criminal offence to sell, supply or import any medicinal product containing kava for human consumption. It is legal to possess kava for personal use, or to import it for purposes other than human consumption (e.g. for animals).
In 2002 Health Canada issued an order prohibiting the sale of any product containing kava. While the restrictions on kava were lifted in 2012, Health Canada has not licensed any kava products for sale in Canada.
In Australia, the supply of kava is regulated through the National Code of Kava Management. The importation and licensing of kava is prohibited in Western Australia. In the Northern Territory, the police say that "the sale and, in majority of circumstances, possession of kava [...] is illegal". The Australian Therapeutic Goods Administration has recommended no more than 250 mg of kavalactones be taken in a 24‑hour period.
Legislation has been proposed to require that kava products be derived only from noble cultivars, which may be less toxic. Other acts have been passed based on the assumption that aqueous solutions are less harmful. Exclusion of certain aerial parts of the plant are also often required by law or convention, which contain less pipermethystine and other toxic compounds.
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- Teschke, Rolf; Sarris, Jerome; Lebot, Vincent (2011-01-15). "Kava hepatotoxicity solution: A six-point plan for new kava standardization". Phytomedicine: International Journal of Phytotherapy and Phytopharmacology 18 (2-3): 96–103. doi:10.1016/j.phymed.2010.10.002. ISSN 1618-095X. PMID 21112196.
- There are many variations to this ceremony; one of which is described in: Biturogoiwasa, Solomoni; Walker, Anthony R. (2001). My Village, My World: Everyday Life in Nadoria, Fiji. Suva, Fiji: Institute of Pacific Studies, University of the South Pacific. pp. 17–20. ISBN 978-982-02-0160-6. There are numerous anthropological studies, one example being: Tomlinson, Matt (2007). "Everything and Its Opposite: Kava Drinking in Fiji". Anthropological Quarterly 80 (4): 1065–81. doi:10.1353/anq.2007.0054.[improper synthesis?]
- Djavaweb (2015-10-25). "New Kava Bars Prove Kava is Growing". Retrieved 2016-07-28.
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- Kilham, Christopher (1996-06-01). Kava: Medicine Hunting in Paradise: The Pursuit of a Natural Alternative to Anti-Anxiety Drugs and Sleeping Pills. Inner Traditions / Bear & Co. ISBN 9780892816408.
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- Lebot, Vincent; Levesque, Joël (1996-09-01). "Genetic control of kavalactone chemotypes in Piper methysticum cultivars". Phytochemistry 43 (2): 397–403. doi:10.1016/0031-9422(96)00209-9.
- Showman, Angelique F.; Baker, Jonathan D.; Linares, Christina; Naeole, Chrystie K.; Borris, Robert; Johnston, Edward; Konanui, Jerry; Turner, Helen (2015-01-01). "Contemporary Pacific and Western perspectives on `awa (Piper methysticum) toxicology". Fitoterapia 100: 56–67. doi:10.1016/j.fitote.2014.11.012. ISSN 1873-6971. PMID 25464054.
- Jerome, Sarris; et al. (2011). "Kava: A Comprehensive Review Of Efficacy, Safety, And Psychopharmacology". Australian and New Zealand Journal of Psychiatry 45: 27–35. doi:10.3109/00048674.2010.522554. PMID 21073405.
- Sarris, Jerome; Stough, Con; Bousman, Chad A.; Wahid, Zahra T.; Murray, Greg; Teschke, Rolf; Savage, Karen M.; Dowell, Ashley; Ng, Chee (2013-10-01). "Kava in the treatment of generalized anxiety disorder: a double-blind, randomized, placebo-controlled study". Journal of Clinical Psychopharmacology 33 (5): 643–648. doi:10.1097/JCP.0b013e318291be67. ISSN 1533-712X. PMID 23635869.
- Pittler MH, Ernst E (2000). "Efficacy of kava extract for treating anxiety: systematic review and meta-analysis". J Clin Psychopharmacol 20: 84–89. doi:10.1097/00004714-200002000-00014.
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- Shinomiya, Kazuaki; Inoue, Toshio; Utsu, Yoshiaki; Tokunaga, Shin; Masuoka, Takayoshi; Ohmori, Asae; Kamei, Chiaki (2005-07-01). "Effects of kava-kava extract on the sleep-wake cycle in sleep-disturbed rats". Psychopharmacology 180 (3): 564–569. doi:10.1007/s00213-005-2196-4. ISSN 0033-3158. PMID 15700178.
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- Tang, Yaxiong; Simoneau, Anne R.; Xie, Jun; Shahandeh, Babbak; Zi, Xiaolin (2008-11-01). "Effects of the kava chalcone flavokawain A differ in bladder cancer cells with wild-type versus mutant p53". Cancer Prevention Research (Philadelphia, Pa.) 1 (6): 439–451. doi:10.1158/1940-6207.CAPR-08-0165. ISSN 1940-6215. PMC 2830727. PMID 19138991.
- Triolet, Julie; Shaik, Ahmad Ali; Gallaher, Daniel D.; O'Sullivan, Michael G.; Xing, Chengguo (2012-08-01). "Reduction in colon cancer risk by consumption of kava or kava fractions in carcinogen-treated rats". Nutrition and Cancer 64 (6): 838–846. doi:10.1080/01635581.2012.689917. ISSN 1532-7914. PMID 22693990.
- Johnson, Thomas E.; Hermanson, David; Wang, Lei; Kassie, Fekadu; Upadhyaya, Pramod; O'Sullivan, Michael G.; Hecht, Stephen S.; Lu, Junxuan; Xing, Chengguo (2011-01-01). "Lung tumorigenesis suppressing effects of a commercial kava extract and its selected compounds in A/J mice". The American Journal of Chinese Medicine 39 (4): 727–742. doi:10.1142/S0192415X11009202. ISSN 0192-415X. PMID 21721153.
- Sarris, J; Laporte, E; Schweitzer, I (2011). "Kava: A comprehensive review of efficacy, safety, and psychopharmacology". The Australian and New Zealand Journal of Psychiatry 45 (1): 27–35. doi:10.3109/00048674.2010.522554. PMID 21073405.
- United States Centers for Disease Control and Prevention (2002). "Hepatic Toxicity Possibly Associated with Kava-Containing Products – United States, Germany, and Switzerland, 1999 2002". Morbidity & Mortality Weekly Report 51 (47): 1065–1067. Retrieved 16 September 2005.
- Center for Food Safety; Applied Nutrition (2002). "Kava-Containing Dietary Supplements May Be Associated with Severe Liver Injury". United States Food and Drug Administration. Archived from the original on 25 March 2008. Retrieved 16 June 2005.
- Baker, Jonathan (2011). "Tradition and toxicity: Evidential cultures in the kava safety debate". Social Studies of Science 41: 361–384. doi:10.1177/0306312710395341.
- Showman; et al. (2014). "Contemporary Pacific and Western perspectives on `awa (Piper methysticum) toxicology.". Filoterapia 100: 56–67. doi:10.1016/j.fitote.2014.11.012. PMID 25464054.
- "Kava: A Human Health Risk Assessment" (PDF). Technical Report Series No 30 (Food Standards Australia New Zealand). 2016-05-25.
- Pantano, Flaminia; Tittarelli, Roberta; Mannocchi, Giulio; Zaami, Simona; Ricci, Serafino; Giorgetti, Raffaele; Terranova, Daniela; Busardò, Francesco P.; Marinelli, Enrico (2016-04-16). "Hepatotoxicity Induced by "the 3Ks": Kava, Kratom and Khat". International Journal of Molecular Sciences 17 (4). doi:10.3390/ijms17040580. ISSN 1422-0067. PMC 4849036. PMID 27092496.
- University of Maryland Medical Center (2011). "Kava Kava". Retrieved 18 December 2011.
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- Izzo AA, Ernst E. Interactions between herbal medicines and prescribed drugs: a systematic review" Drugs 2001;61(15):2163-75.
- Clough A (2001). "Enough! or too much. What is 'excessive' kava use in Arnhem Land?". Drug Alcohol Rev 22 (1): 43–51. doi:10.1080/0959523021000059820. PMID 12745358.
- Mathews JD, Riley MD, Fejo L, et al. (June 1988). "Effects of the heavy usage of kava on physical health: summary of a pilot survey in an aboriginal community". Med. J. Aust. 148 (11): 548–55. PMID 3374423.
- Kava R (March 2001). "The adverse effects of kava". Pac Health Dialog 8 (1): 115–8. PMID 12017812.
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- Ruze, P. (1990-06-16). "Originally published as Volume 1, Issue 8703Kava-induced dermopathy: a niacin deficiency?". The Lancet 335 (8703): 1442–1445. doi:10.1016/0140-6736(90)91458-M.
- Norton, Scott A.; Ruze, Patricia (1994-07-01). "Kava dermopathy". Journal of the American Academy of Dermatology 31 (1): 89–97. doi:10.1016/S0190-9622(94)70142-3.
- "Vanuatu - Legislation - Kava Act 2002". faolex.fao.org. Retrieved 2016-07-02.
- "Standard 2.6.3 – Kava – Food Standards (Proposal P1025 – Code Revision) Variation—Australia New Zealand Food Standards Code – Amendment No. 154 - 2015-gs1906 - New Zealand Gazette". gazette.govt.nz. Retrieved 2016-07-02.
- "Europe Explains Its Stand on Kava from the Pacific". Radio Australia. March 2012. Retrieved 10 October 2013.
- C.I.J.M. Ross-van Dorp (2003). "Besluit van 23 april 2003, houdende wijziging van het Warenwetbesluit Kruidenpreparaten (verbod op Kava kava in kruidenpreparaten)" (PDF). Sdu Uitgevers. Staatsblad van het Koninkrijk der Nederlanden. Retrieved 7 February 2007.
- "Fiji takes kava ban fight to WTO". The World Trade Review. August 2005. Retrieved 26 October 2013.
- Bowman, Chakriya. "The Pacific Island Nations: Towards Shared Representation". WTO. Retrieved 26 October 2013.
- Comeback unter strengen Auflagen(in German). PHARMAZEUTISCHE ZEITUNG online 16/2015. Retrieved February 28, 2016.
- "New Kava Challenge". Vanuatu Daily Post. Retrieved 2016-03-03.
- "The Medicines for Human Use (Kava-kava) (Prohibition) Order 2002". Retrieved 26 October 2013.
- "Marketed Health Products Directorate Heath Products and Foods Branch". Canadian Adverse Reaction Newsletter (Health Canada) 12 (4). 2002.
- "Listing of Drugs Currently Regulated as New Drugs (The New Drugs List)". www.hc-sc.gc.ca. Health Canada. 6 November 2012. Retrieved 19 March 2014.
- "National Drug Strategy - Aboriginal and Torres Strait Islander Peoples Complementary Action Plan 2003–2009 - Background Paper". Ministerial Council on Drug Strategy, Commonwealth of Australia, May 2006. ISBN 0 642 82328 6.
- "Kava". Government of the Northern Territory of Australia. Archived from the original on 8 January 2013.
In accordance with the Australian Government National Emergency Response in the Northern Territory the commercial importation and licensing of kava is prohibited.
- "Kava in the Northern Territory". Northern Territory Police. Retrieved 26 October 2013.
- "Kava fact sheet". Therapeutic Goods Administration, Government of Australia. April 2005. Retrieved 10 July 2006. (Download PDF 44KB).
- Teschke R, Sarris J, Glass X, Schulze J (March 2011). "Kava, the anxiolytic herb: back to basics to prevent liver injury?". Br J Clin Pharmacol 71 (3): 445–8. doi:10.1111/j.1365-2125.2010.03775.x. PMC 3045554. PMID 21284704.
This raises the question as to whether noble cultivars may be better and safer regarding hepatotoxic effects than the medicinal kava varieties.
- Teschke, Rolf (March 2011). "Kava and the Risk of Liver Toxicity: Past, Current, and Future" (PDF). AHPA Report. Retrieved 26 December 2013.
- Teschke, Rolf; Samuel Qiu; Vincent Lebot (September 2011). "Herbal hepatotoxicity by kava: Update on pipermethystine, flavokavain B, and mould hepatotoxins as primarily assumed culprits". Digestive and Liver Disease 43 (9): 676–681. doi:10.1016/j.dld.2011.01.018. PMID 21377431.
- Lindstrom, Lamont; Lebot, Vincent; Merlin, Mark David (1992). Kava: The Pacific Elixir – The Definitive Guide to its Ethnobotany, History and Chemistry. New Haven, Conn: Yale University Press. ISBN 0-300-05213-8. OCLC 231506209.
- The Mars Trilogy by Kim Stanley Robinson, Spectra, 1993. ISBN 0-553-09204-9. Contains many references to Kava, and "Kavajava" – kava mixed with coffee. The book uses kava as the social drink of choice for the "Martians" (human colonizers of Mars).
- The Sex Lives of Cannibals: Adrift in the Equatorial Pacific by J. Maarten Troost, Broadway Books, New York, 2004. ISBN 0-7679-1530-5.
- Getting Stoned with Savages: A Trip Through the Islands of Fiji and Vanuatu by J. Maarten Troost, Broadway Books, New York, 2006. ISBN 978-0-7679-2199-2. ISBN 0-7679-2199-2.
- Siméoni Patricia; Lebot Vincent (2014). Buveurs de kava. Port-Vila: Editions Géo-consulte. p. 361. ISBN 978-2-9533362-3-8. External link in
|Wikispecies has information related to: Piper methysticum|
|Wikisource has the text of the 1911 Encyclopædia Britannica article Kava.|
- "UNODC - Bulletin on Narcotics: The narcotic pepper - The chemistry and pharmacology of Piper methysticum and related species". United Nations Office on Drugs and Crime. 1973. pp. Issue 2. Retrieved 19 February 2014.
- Kava ban documents
- Piper methysticum information from the Hawaiian Ecosystems at Risk project (HEAR)
- "Kava". Encyclopædia Britannica 14 (9th ed.). 1882.