Kava may not have negative effects on the brain and may improve memory and focus, according to a new study.
Kava beverages, made from dried roots of the shrub Piper methysticum, have been used ceremonially and socially in the South Pacific for hundreds of years and in Europe since the 1700s. Several well-conducted human studies have demonstrated kava's efficacy in the treatment of anxiety with effects observed after as few as one to two doses and progressive improvements over one to four weeks. Preliminary evidence suggests possible equivalence to benzodiazepines.
In a new study, researchers analyzed 10 human trials investigating the changes that kava may cause in the brain. They reviewed studies that were published before June 2010 and explored the link between kava intake and any effects on memory and attention.
One study reported that kava significantly improved both memory and visual attention, while another found that participants had poorer visual attention while performing high-pressure cognitive tasks. A third study linked kava to body sway, or reduced balance.
The researchers reported that none of the studies found significantly negative effects of kava on memory and attention. However, more evidence is needed in order to determine whether kava intake is beneficial for the brain.
Many experts believe that kava is neither sedating nor tolerance-forming in recommended doses. Some trials report occasional mild sedation, although preliminary data from small studies suggest lack of neurological-psychological impairment.
There is growing concern regarding the potential for liver toxicity from kava. Multiple cases of liver damage have been reported in Europe, including hepatitis, cirrhosis and liver failure. Kava has been removed from shelves in several countries due to these safety concerns. The U.S. Food and Drug Administration (FDA) has issued warnings to consumers and physicians. It is not clear what dose or duration of use is correlated with the risk of liver damage. The quality of these case reports has been variable; several are vague, describe use of products that do not actually list kava as an ingredient, or include patients who also ingest large quantities of alcohol. Nonetheless, caution is warranted.
Chronic or heavy use of kava has also been associated with cases of neurotoxicity, pulmonary hypertension and dermatologic changes. Most human trials have been shorter than two months, with the longest study being six months in duration.
For more information about kava, please visit Natural Standard's Foods, Herbs & Supplements Database.