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.