(See also Overview of Medicinal Herbs and Nutraceuticals.)
Kava comes from the root of a shrub that grows in the South Pacific. It is ingested as a tea or in capsule form.
Over 20 people in Europe developed liver toxicity (including liver failure) after taking kava. Thus, the Food and Drug Administration (FDA) has required a warning label on kava products, and safety is under continuing surveillance.
When kava is prepared traditionally (as tea) and used in high doses or over long periods of time, a scaly rash (kava dermopathy), vision problems, changes in blood (such as an increased number of red blood cells), and changes in movement disorders (such as worsening of Parkinson disease) may occur.