Nature's Pharmacopeia: A World of Medicinal Plants


Piper methysticum

From its Polynesian center of origin, kava was long ago dispersed by oceangoing peoples, eventually reaching islands across a vast portion of the Pacific, including parts of Micronesia, New Guinea, and much of Polynesia as far east as Hawai‘i.228 It is a perennial plant that produces many branched narrow stems bearing heart-shaped leaves and a tangled mass of medicinally useful roots underground (figure 14.31). Allowed to grow for five or more years, the plant can reach a height of up to 5 or 6 meters, but the roots are typically harvested from plants two to three years of age, at a height of around 2 to 2.5 meters.229Although kava occasionally grows small, spike-like flowering structures, the species is sterile and can be reproduced only through cuttings.230 Therefore, it is thought to exist solely in cultivation.231 Kava was domesticated perhaps 3000 years ago and now grows as dozens of varieties distinguished by coloration, growth habit, and medicinal properties.232


FIGURE 14.31   Kava.

Kava’s importance to social groups across the Pacific is recorded in legend and in the beliefs of people who employ the plant as a mediator of spiritual and community bonds. To many people of Oceania, kava is thought to be a gift of powerful ancestors or gods, sacred in origin and function.233 The plant has most notably been incorporated into numerous traditional rituals, during which the roots are pounded or chewed, the resulting liquid collected and then consumed in customary tribal settings (figure 14.32).234 Kava produces a sense of relaxation and altered sensory experiences perceived as a means to communicate with ancestors.235 It is also offered as a tribute to people of high social rank, shared between men to ease negotiations of a political or economic nature, and used to commemorate community events such as marriages, funerals, and initiation ceremonies.

In modern-day Pacific island cultures, kava is frequently consumed as a recreational beverage. For example, the islands of Vanuatu are dotted with small kava bars called nakamals where people gather, typically in the evenings, to consume freshly prepared kava.236 In addition to kava’s social and recreational roles, numerous medicinal uses have been recorded, including the treatment of female reproductive concerns, urinary problems, and many types of infections.237

European explorers of the eighteenth century and Christian missionaries of the nineteenth and twentieth centuries disapproved of the kava ritual and its accompanying inebriation. As they evangelized the peoples of the Pacific, they discouraged the consumption of kava, considering it an impediment to the moral development of the indigenous groups.238 Despite the religious proscriptions imposed against kava in Oceania, the European and North American medical community of the early twentieth century brought the herb into its materia medica.239 For example, the Parke-Davis pharmaceutical company recommended kava extracts to treat “gout, bronchitis, catarrhal affections” and “especially … acute gonorrhea.” At a low dose, the drug was “a stimulant and tonic,” according to the company experts, and at a larger dose, it produced “intoxication of a silent and drowsy nature accompanied by incoherent dreams.”240


FIGURE 14.32   Young women preparing kava in Samoa, 1916. (Photograph by A. J. Tattersall; Picture Collection, New York Public Library, Astor, Lenox and Tilden Foundations)

By the late twentieth century, kava production in many parts of the Pacific rebounded as self-governance developed and missionary zeal waned.241 While kava’s ritual and social uses remained important among local peoples, interest in kava rose particularly among Europeans and North Americans for its potential anxiety-reducing properties. Numerous companies imported large quantities of kava root for the manufacture of mood-altering supplements.242

Kava’s effects on sensation, perception, and mood are attributed primarily to an assortment of fat-soluble compounds called kavalactones.243 The chemicals exert a local anesthetic effect when absorbed through the skin and a general analgesic property when consumed orally.244 In clinical trials, kava extracts have been shown to reduce anxiety among volunteer participants, an effect probably mediated by kavalactone binding to GABA neurotransmitter receptors in the brain.245 Kavalactones also produce effects on the adrenergic neurotransmitter system.246

While kava has a long history of spiritual, social, and medicinal use in Oceania, along with a growing body of research indicating its mechanism of action and therapeutic efficacy, some questions have been raised about kava’s environmental impacts and safety. With the revival of interest in kava on the Pacific islands during recent decades, farmers have expanded the cultivation of the plant at the expense of forested land, which threatens the islands’ delicate ecosystems.247 Furthermore, questions were raised about the safety of kava-containing products.

During the 1990s and early 2000s, Western regulators noted an association between kava use and liver damage among several dozen patients.248 As a result, governments, including those of Great Britain, Germany, and Canada, banned the sale of kava products; in the United States, the FDA issued an advisory letter warning of kava’s potential risks.249 While the connection between kava constituents and liver damage remains unclear, some researchers speculate that differences in preparation method might account for possible health risks with imported kava. For example, it is possible that some of the dried kava material shipped overseas from Micronesian and Polynesian islands might not be of the same cultivated varieties as the kava consumed by locals and might include material other than the roots. Also, rather than preparing kava in a water-based drink, as is the Pacific custom, many Western companies extract the presumed active principles using organic solvents. These differences in preparation might account for differences in chemical profile, perhaps explaining an increased health risk.250

While researchers in the West continue to investigate the efficacy and safety of kava, it remains a plant of great cultural value in the Pacific. Many generations ago, people carried the plant from island to island, a living connection to a world of ancestors and gods, a mediator of social, spiritual, and physical health. Under the microscope of contemporary science, the herb’s medical usefulness remains incompletely tested, and much more investigation awaits.

Thousands of years of tasting and sniffing, grinding and steeping, and trial and error have given humanity a set of medicinal plants that serve health in the form of spices, herbal teas, lotions, and foods. While some herbs declared their effectiveness early in human history, others came more recently into common use. Yet all have transformed the way people eat, drink, conduct commerce, and view their health through diverse traditional medical systems. With the advent of a biochemical understanding of drug efficacy comes a new set of challenges. Of the many possible active principles in a root, leaf, stem, seed, or fruit, which ones might be responsible for physiological effects? Of the therapeutic properties gleaned from ancient texts, folk wisdom, and traditional practices, which might be supported by robust, controlled clinical trials? How should such plants and their extracts be regulated: as foods, dietary supplements, or drugs? The future of ancient medicinal plants in modern society expects that such questions be addressed in an integrated, multidisciplinary fashion.