• doi: 10.3390/nu12103044
• Published online 2020 Oct 5

Tengfei Bian,^1,†Pedro Corral,^1,†Yuzhi Wang,^1,†Jordy Botello,^1,†Rick Kingston,²Tyler Daniels,³Ramzi G. Salloum,⁴Edward Johnston,⁵Zhiguang Huo,⁶Junxuan Lu,⁷Andrew C. Liu,⁸ and Chengguo Xing^1,

Abstract

Kava beverages are typically prepared from the root of Piper methysticum. They have been consumed among Pacific Islanders for centuries. Kava extract preparations were once used as herbal drugs to treat anxiety in Europe. Kava is also marketed as a dietary supplement in the U.S. and is gaining popularity as a recreational drink in Western countries. Recent studies suggest that kava and its key phytochemicals have anti-inflammatory and anticancer effects, in addition to the well-documented neurological benefits. While its beneficial effects are widely recognized, rare hepatotoxicity had been associated with use of certain kava preparations, but there are no validations nor consistent mechanisms. Major challenges lie in the diversity of kava products and the lack of standardization, which has produced an unmet need for quality initiatives. This review aims to provide the scientific community and consumers, as well as regulatory agencies, with a broad overview on kava use and its related research. We first provide a historical background for its different uses and then discuss the current state of the research, including its chemical composition, possible mechanisms of action, and its therapeutic potential in treating inflammatory and neurological conditions, as well as cancer. We then discuss the challenges associated with kava use and research, focusing on the need for the detailed characterization of kava components and associated risks such as its reported hepatotoxicity. Lastly, given its growing popularity in clinical and recreational use, we emphasize the urgent need for quality control and quality assurance of kava products, pharmacokinetics, absorption, distribution, metabolism, excretion, and foundational pharmacology. These are essential in order to inform research into the molecular targets, cellular mechanisms, and creative use of early stage human clinical trials for designer kava modalities to inform and guide the design and execution of future randomized placebo controlled trials to maximize kava’s clinical efficacy and to minimize its risks.

Keywords: kava, kavalactone, cultivars, quality control, quality assurance, stress, anxiety, cancer, hepatotoxicity, inflammation

1. Introduction

Kava, also known as kava kava, ‘Awa, or ‘awa, is a type of perennial shrub that belongs to the pepper family, known as Piperaceae [1]. Piper methysticum is its botanical name, which derives from the Latin “methysticum”. In the local language and culture, the word “kava” is used to denote something “bitter”. Kava is native to Oceania, with important cultural and historical significance. It has been grown throughout the regions of Micronesia, Polynesia and Melanesia for its relaxant and medicinal effects as a pain reliever, muscle relaxant, and as a remedy for anxiety, nervousness and insomnia. Kava has been domesticated in these regions for thousands of years [2] (Figure 1a). Female flowers of kava are scarce and fruit pollination is not particularly productive. Kava is cultivated by propagation from stem cuttings [3]. It has over one hundred different chemotypes and cultivars. A set of lactones are abundant and present almost exclusively in kava, thus named kavalactones. These kavalactones are also believed to be responsible for the health benefits of traditional kava preparations [4]. Their fingerprints have also been used to distinguish different kava cultivars. The sum of the six major kavalactones has been used to standardize different kava products. Kava is consumed in the traditional form as a beverage, in a more merchandized form as either an anxiolytic agent or a dietary supplement, or more recently as a recreational drink served in kava bars.

Reference:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7600512/