The FDA won't classify all natural supplements as drugs or validate any of their benefits because they don't want to step on The Drug companies toes.

Was available freely in UK until about five years ago. Taken off the shelves after reports of extreme liver toxicity associated with over-usage.

What does it contain to cause an effect on brain and liver?

"A majority of experts say the potential side effects are dose dependent,'' he said. Most German kava products give a daily dosage level of 60 to 120 mg of kavapyrones, and doctors may recommend dosages as high as 240 mg per day, yet three of the four people who received liver transplants were taking more than 240 mg per day.

Kava affects the liver by causing a shift in enzymes, especially cytochrome P450. However, this enzyme shift is not unusual -- it occurs after every meal. Even a glass of grapefruit juice causes a similar shift.

I imagine it's the size of the "shift" that's the problem.