Unsolved mystery of kava toxicity

The article appears in American Chemical Society's journal Chemical Research in Toxicology.

Line Olsen and colleagues point out that for centuries, people of the Pacific Islands have safely consumed a beverage made from crushed kava roots. Kava'scalming effects made it popular in Western cultures in the 1990s, when people also began to use a herbal supplement for the treatment of anxiety, emotional stress and sleep problems. But in 2001, reports of liver damage among Westerners who took kava supplements gained widespread attention. Many Western countries, including the United States, the United Kingdom, and Canada, ban or regulate the sale of kava products. To determine why kava is toxic to some people but not to others, the researchers sifted through the scientific studies published on the topic.

Their review of 85 scientific studies on kava toxicity found no consensus on kava toxicity, despite several theories that have emerged over the years. Culprits include methods for preparing kava, the particular species of kava used, the possible toxicity of substances produced by the body when kava is digested and genetic differences among consumers. "To date, there remains no indisputable reason for the increased prevalence of kava-induced hepatotoxicity in Western countries," the researchers say.