Scientists are finding promise of a bladder cancer treatment -- one of the most common cancers in the U.S. -- in a South Pacific root called kava.
Dr. Xiaolin Zi, an associate professor of urology at the University of California, Irvine, noticed that while cigarette smoking is a leading cause of bladder cancer, the western Pacific Islands see a relatively low incidence of bladder cancer despite high smoking rates. He thinks kava might have something to do with it.
Traditionally ground and turned into a drink for its relaxing qualities, kava contains compounds called flavokawains, which Zi has shown to stop bladder tumor growth in cell cultures and animal studies. Flavokawains, Zi believes, might also help slow or prevent bladder cancer in humans.
Kava has been used for thousands of years throughout the Pacific Islands as a social and ceremonial beverage; in the Hawaiian culture specifically, it is called `awa. The roots of the plant are fashioned into a drink and are believed to relieve anxiety, relax muscles, and improve sleep. Native cultures, like those in Fiji, sip and share kava drinks during important meetings -- reportedly to calm nerves and reduce possible conflict.
Currently, Zi is focusing on the kava compound flavokawain A. His team has used mouse models of bladder cancer to demonstrate how the compound protects against the carcinogenic effects of tobacco. They found that flavokawain A encourages cell death in precancerous cells by overcoming the effects of the mutated p53 protein -- a protein that plays a critical role in keeping cells from becoming cancerous.
Zi's study set out to show that mice fed high doses of the kava compound experience slower tumor growth. So far, all three bladder cancer mouse models have responded to the treatment.
Kava gained fame in western cultures when it was marketed as an herbal treatment because of its calming effects. However, the root has been linked to some cases of liver damage, though the jury is still out on whether it's the actual kava that caused the liver damage, or if it was the taking of the root with other drugs/herbs. The FDA has issued a warning that the root carries a rare but potential liver failure risk.
A 2011 review of kava in the journal "Chemical Research in Toxicology" sought to explain why Pacific Island people could consume kava safely for centuries while people in the U.S., Europe and other western nations sometimes experienced toxic effects. The review found no consensus on kava toxicity, although several theories have emerged, including deviations in the traditional methods of preparing kava and the particular species of plants being used.
So far in his research, Zi has not seen any evidence of toxicity from the kava compound, and he is hopeful for its potential use as a treatment for human bladder cancer patients.
"The majority of bladder cancer occurs after age 65," Zi, who is also a member of UC Irvine's Chao Family Comprehensive Cancer Center, said in a statement. "Any agents that can delay the onset of cancer are highly beneficial. ... For older people, being cancer-free for years longer dramatically improves quality of life."
Because many bladder cancer treatments come with uncomfortable side effects, Zi hopes that treatments derived from natural sources could carry fewer side effects.
"Although there are not yet a lot of studies showing the cancer-fighting effectiveness of natural treatments, many cancer patients are using them," Zi said in the statement. "More studies are needed to find out if these natural supplements work and in what circumstances people should use them. There's a lot of exciting potential in this area of research."
Zi is hoping to conduct clinical trials on human patients with the kava compound in the near future. Meanwhile, other studies are being conducted hoping produce similar results on the compound's effects on lung cancer.