If you’ve ever considered taking an herbal remedy under the theory that it can’t hurt and it might help, read this: A study published online Monday by the Proceedings of the National Academy of Sciences reports that people who thought they were taking a harmless weight-loss supplement wound up with a type of bladder cancer as a result.

The researchers, from the U.S. and Taiwan, point the finger at an herbal ingredient called aristolochic acid, or AA. It comes from plants, including wild ginger (Asarum canadense), that have been used in Chinese medicine to treat “stomach ailments, to restore a woman’s energy after the birth of a child, to treat cough, allergy and breathing problems, and in some weight-loss formulas,” according to this 2009 story from the Los Angeles Times Health section.

Scientists have been suspicious of AA for more than a decade. Back in 2000, the U.S. Food and Drug Administration warned healthcare professionals that aristolochic acid could cause cancer and kidney damage. It issued a follow-up letter the next year and also warned manufacturers of herbal supplements to avoid using AA in their products, which aren’t regulated by the government. But in 2003, researchers at UC Berkeley told the FDA that they found 112 herbal products available for sale on the Web that either contained or were likely to contain the controversial ingredient, according to the L.A. Times story.

As Melissa Healy reported:


“The danger of aristolochic acid came to light when more than 100 women participating in a weight-loss program in Belgium developed kidney damage and urinary tract cancers. All had been prescribed an herbal weight-loss remedy that contained it. Though banned throughout Europe and in Japan, Aristolochia extracts continue to be used widely in China. Any product bearing the species name ‘Aristolochia,’ ‘Bragantia’ or ‘Asarum’ should be avoided.”

The country with the highest incidence of upper urinary tract urothelial carcinomas is Taiwan, according to the new PNAS study. Taiwan is also a place where herbs containing AA have been popular for a long time. So researchers looked for a link between the two.

They compared 151 patients with the urothelial cancers to a “control” group of 25 patients with a type of kidney cancer called renal cell carcinoma. They found that aristolochic acid prompted a specific type of mutation on a tumor suppressor gene known as TP53 – a mutation that leads to urothelial cancer. They concluded that the widespread use of AA-containing plants in Chinese herbal medicine is a significant factor in the growth of urothelial cancers in Taiwan over the past quarter century.

The researchers noted that one-third of people in Taiwan have received a prescription for an herbal medicine containing AA, and a lot more people probably have been exposed to it through over-the-counter products. Epidemiological evidence suggests that the more AA people consume over a lifetime, the more likely they are to develop urothelial cancers, they wrote. What’s more, the ingredient is also common in China and elsewhere in Asia – and once exposure to AA causes the dangerous genetic change, people’s risk of developing urothelial cancer remains “significant” for the rest of their lives.


The result, they wrote, is “an international public health problem of considerable magnitude.”

You can read the paper online here.

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