Kava (Piper methysticum) was once one of the bright lights in the herbal industry, showing great promise for promoting relaxation and reducing anxiety in users. But German studies published in 2001 suggested a link between kava use and liver damage. The studies led to Federal Drug Administration warnings on kava use in this country, and to an outright ban on products in Germany and other European countries containing more than a minute amount of kava.
Now a new study conducted at the University of Hawaii at Manoa suggests that kava root—the part of the plant traditionally used—may not be the main culprit in the well-documented links between kava and such ailments as hepatitis and cirrhosis. The research gives at least a glimmer of hope to the beleaguered kava industry, though more studies will be needed to prove that kava is safe for consumers.
C.S. Tang, Ph.D., the lead researcher on the new kava study, said that kava's liver toxicity is not a result of kavalactones, the active ingredient found in the plant's root, but of an alkaloid known as pipermethystine. "This compound is not found in the roots or even in the inside of the stem," Tang said, "but only in the green part, the peelings and leaves."
Tang said his research team found evidence that supplements manufacturers commonly purchased leaves and stems—parts of the plant never used traditionally—during the height of the kava boom, and that these ingredients might be to blame for the link between kava products and liver damage.
However, the link between pipermethystine and liver damage may not, by itself, vindicate the use of kava root. Mark Blumenthal, president of the American Botanical Council, based in Austin, Texas, cautioned that leaves and stem peelings shouldn't have been used in the first place. "This is interesting research, but we're not buying into it yet," Blumenthal said. "Kava stems and peelings are not pharmacopeia-grade in European countries. The pharmacopeia specifically stipulates the rhizome, so companies that follow the standards—which most reputable companies do—would not use [other parts of the plant]." Kava root is the only part of the plant legally allowed in U.S.-manufactured supplements as well.
However, kava is included on the list of GRAS [generally recognized as safe] ingredients for dietary supplements because of its long history of traditional use without known side effects. "Kava drinkers in Hawaii use a much heavier dose than those who use capsules, and use it more regularly," Tang said. "It seems unlikely that a carefully made product from the roots in a much lower dosage could have an acute effect. It's not logical."
Blumenthal said that many of the German case studies linking kava and liver damage had other confounding factors, including heavy alcohol use and prior liver disease in participants, though a handful of cases of adverse effects in participants were clearly linked solely to kava use.
Traditional healers and Western physicians in Samoa participated in a new study soon to be published in Herbalgram magazine, which backs the idea that traditional use of kava root does not, in itself, lead to liver problems. "The doctors and the traditional healers found no link between kava use and liver problems, except in those who drank substantial amounts of alcohol," Blumenthal said. "There may be a kava-alcohol synergy, suggested previously, that needs to be fully explored."
Blumenthal said that, while the Hawaiian researchers' hypothesis could well turn out to be correct, he fears that "people are going to be jumping at the first opportunity to have a facile explanation to get kava off the hook, and we don't know ultimately if that will hold water."
"This is a working hypothesis," Tang cautioned. "At this point we know that the alkaloid pipermethystine is far more harmful to the liver-cell culture in vitro than kavalactones. To tell the truth, we don't yet have sufficient data to understand." That, said Blumenthal, is the point. But this new research is a positive step toward re-establishing the legitimacy of kava as an effective dietary supplement.
Mitchell Clute is a poet, musician and freelance writer based in Paonia, Colo.