University of Hawaii scientists may have an answer as to why kava kava, consumed as a beverage by Pacific Islanders for 2000 years, has only recently been associated with liver toxicity.
According to the team of scientists headed by Dr. C.S. Tang at the University of Hawaii - Manoa, an alkaloid compound found in the stem peelings and leaves, pipermethystine, has a 'strong negative effect' on liver cells.
The beverage consumed by islanders is made from kava kava root, rather than peelings or leaves. It is speculated that products on the market may contain non-root material, and this may account for the liver problems recently observed, which led banning of kava products in many markets around the world. According to an article in Florida Today, it wasn't until recent demand increases (2000 and 2001), that non-root materials were traded and presumably used as raw materials.
Article in Florida Today: