Washington ? A 45-year-old woman became jaundiced and then, in just months, became so ill she needed a liver transplant. Her doctor suspects the herbal supplement kava.

European health officials report 25 similar cases of liver toxicity, and some countries are barring kava sales. Now the Food and Drug Administration is investigating whether the herbal sedative promoted to relieve anxiety, stress and insomnia poses a danger.

Under review are 38 Americans, including the transplant recipient, with medical problems possibly associated with kava use. FDA scientists cannot yet say if the blockbuster seller is to blame.

“The jury’s still out on kava,” agrees Mark Blumenthal of the American Botanical Council, which joined industry groups in hiring a toxicologist to investigate.

Already Canada has urged consumers not to take kava until the question of its safety is settled; sales have halted in Switzerland and Britain; Germany is acting to make kava a prescription drug. Here, the National Institutes of Health has suspended two kava studies.

And the FDA’s inquiry has made some startling findings on how Americans use largely unregulated supplements. FDA records show that:

l Two 13-year-olds had to be hospitalized after using kava, one when the sleep-inducing herb apparently interacted with an anesthetic her dentist used on her and the other whose doctor reported she took a deliberate overdose.

l A woman suffering kidney and liver problems used more than 20 supplements and other over-the-counter remedies, handfuls of pills a day.

Dangers of mixing

Aside from the difficulty of teasing out kava’s role, no one knows how dangerous it is to mix all these pills willy-nilly and take such high doses, says FDA dietary supplement chief Dr. Christine Taylor.

Worse, “kids who are still developing their use of this is of particular concern. They’re vulnerable,” she warns.

It’s the latest bad news for the $16 billion supplement industry, which reported sharp sales declines last year.

Under federal law, no one has to prove dietary supplements are safe or work as advertised before selling. The FDA’s $9 million supplement division instead investigates problems and tries to curb use of products it can prove dangerous.

Mystery effects

While kava is sold as a natural alternative to prescription anxiety relievers, little is known about how it works, says Dr. Jonathan Davidson of Duke University, who hopes his NIH-suspended study will resume to answer those questions.

No serious side effects arose in studies where people took only kava for short periods, he says, but “the core of the problem is we really don’t know very much about the way kava interacts with other medicines.”

Kava, a member of the pepper family, has long been used as a ceremonial drink in the South Pacific. Used sporadically, its biggest danger seemed to be if people drank too much of the sedative before driving.

Then, about two years ago, kava in pill form suddenly boomed, bringing in about $30 million in sales, and Europe reported liver damage.