The milder, more medicinal effects of kava were overshadowed for some time, as English explorers who visited the South Seas described natives going into a stupor and falling asleep after drinking several cups of kava. Because of this, they gave the plant the botanical name Piper methysticum, or intoxicating pepper. The native word, kava, refers to its sharp, pungent taste.

In order to become so sedated on kava that you pass out, you would have to drink nearly toxic amounts, says Irene Catania, N.D., a naturopathic doctor and homeopathic practitioner in Ho-Ho-Kus, New Jersey. "The natives were literally overdosing on it," she says. "When you take kava medicinally, you use only a fraction of that amount, and it doesn’t have an intoxicating effect."

In lower doses, kava helps to benefit the brain, relieve anxiety, and act as a mild sedative or tranquilizer. Unlike many pharmaceutical drugs used for anxiety, such as diazepam (Valium) and alprazolam (Xanax), kava doesn’t space you out or leave you with a kind of hangover, says Dr. Catania.

"That’s one of the real benefits of kava. It’s relaxing but not depressing. It doesn’t deteriorate your mood," she says. "Most people feel more alert and have increased mental acuity."

Kava is good medicine any time there is anxiety from stress, mild depression, a phobia, premenstrual syndrome, or menopause. It also helps with insomnia when anxiety causes sleeplessness, says Dr. Catania. "The way it helps people get to sleep is by relaxing them and decreasing their anxiety level," she says.

Traditionally, only the main root of kava was used medicinally, but the lateral roots, sprouts, and peelings of the interior and exterior bark also contain active ingredients. What apparently brings on feelings of well-being is a group of chemicals known as kavalactones. They are especially abundant in the fat-soluble resin of the roots.

When researchers isolated kavalactones from the kava and gave study subjects only this one group of chemicals the tranquilizing effects were not as pronounced. People seemed to get more benefit when they took an extract that contained all of the ingredients. That may indicate that other chemicals are at work in addition to kavalactones, or it may be that kavalactones are more bioavailable—that is, more quickly taken up by the body—when taken in extract form.

Several European countries have approved kava extract to treat nervous anxiety. The extract is standardized to 70 percent kavalactones. Exactly how kava works in the brain is still a bit of a mystery. What’s clear is that it goes about its business differently than pharmaceutical drugs. Valium binds to certain receptor sites in the brain, which then change the chemical makeup of the brain itself.

Animal studies show that kava affects the limbic system, an ancient part of the brain and the principal seat of emotions. In other words, it may alter the way emotions are processed rather than having a tranquilizing, depressing action.

"Because it doesn’t bind to the receptors, it also can be used a lot more safely than the anti-anxiety drugs," says Priscilla Evans, N.D., a naturopathic doctor at the Community Holistic Center in Chapel Hill, North Carolina. "Kava is nonaddictive, and you don’t build up a tolerance to it as you do with drugs."

Kava's lack of side effects and its ability to relieve anxiety show up in several European studies. In one study, 58 patients who had anxiety were given either a very large dose of kava extract or an ineffective substitute that contained no kava (a placebo). The participants’ anxiety levels were measured with standard psychological assessment tests. After just four weeks, the patients taking the kava showed a statistically significant reduction in feelings of nervousness. They also had fewer complaints related to anxiety, such as heart palpitations, chest pain, headaches, and dizziness. In addition, they reported no side effects from the kava extract.

In another study, German researchers tested kava extract with a group of 101 patients who had a range of anxiety and tension disorders. For 25 weeks, half of the group received a dried kava extract containing 70 percent kavalactones; the other half received a placebo. Once again, the group receiving kava showed significant mood improvement as compared to those given only a placebo.

Kava’s calming action occurs not only in the brain but also throughout the body. It has a pronounced antispasmodic or relaxing effect on skeletal muscles. Dr. Evans sometimes uses kava just to relieve muscle tension brought on by emotional stress or physical work. "It’s effective for acute and chronic muscle spasms and tension," she says. Dr. Catania has also successfully used kava to treat people who have gastrointestinal problems such as nausea or stomach pain that’s caused by anxiety.

Kava is available in dried bulk form and as capsules and tinctures. Medicinal doses are generally no higher than 210 milligrams of kavalactones daily. In comparison, one cup of a typical kava drink as used traditionally in the South Pacific contains about 250 milligrams of kavalactones, and several cups are usually consumed at one sitting.