Birthwort Cancer Risk: People Are Still Eating One of the Most Dangerous Plants on Earth as a Traditional Medicine

Creative Commons Birthwort
A chemical in this birthwort plant, or Aristolochia baetica, has been linked with cancer. A new paper shows it’s responsible for a staggering number of liver cancer cases in two Taiwanese hospitals. Flickr user gailhampshire, via Wikimedia Commons

Updated | Don't eat birthwort. Because if you do, you might be increasing your risk for certain kinds of cancers or kidney problems.

This particular herb has been used as a folk remedy for snakebites and other conditions, Steven Rozen told Newsweek. Rozen is a cancer genomics specialist at the Duke–NUS Medical School in Singapore. He and his colleagues looked at 98 samples of liver cancers from Taiwan and found high rates of a particular, uncommon genetic mutation that scientists already knew was associated with birthwort. The researchers published their findings in Science Translational Medicine on Wednesday.

Without genetic sequencing techniques, the link between birthwort and cancer may have remained undiscovered because it can take years for cancer to develop, Rozen said. There are four letters of the genetic alphabet: A, T, G and C. A chemical found in the plant, aristolochic acid, can glom on to an A DNA base and make it a T instead.

This kind of transversion mutation is quite rare, Rozen said. The body's natural repair process can correct the mutation, but it will usually only do that on one of the two DNA strands. These two factors combined to create a genetic signature of the herb's involvement in the cancer.

The researchers also compared their data to previously reported findings. Of all the reporting countries, clinics or regions, Taiwan had the higher proportion of cases with this signature.

"I thought we would see 10 to 20 percent of liver cancers with AA mutations in them. Instead, we saw over 75 percent with AA mutations in them. I was very surprised at that," Rozen said. China and Southeast Asian countries also reported relatively high proportions of cases that could be linked to the herb.

Birthwort etching
This etching of a birthwort plant, specifically Aristolochia hyperborea, was done by Frederick Smith around 1834. China and Southeast Asian countries reported relatively high proportions of cancer cases that could be linked to the herb. Wellcome Library, London

This study was not an epidemiological survey. Rozen and his colleagues didn't have clinical data that exactly matched the tumor samples, so there was no way to know if patients had actually taken the herb, despite what their tumor's mutational signature indicated. And no conclusions can be drawn from this data about the extent to which taking this herb might elevate a person's risk. "We don't have a baseline," he said, "we don't know how many people have livers that were exposed to AA but never got cancer."

The connection between aristolochic acid and health problems first came to light in 1998 after hundreds of women were poisoned with it at a Belgian weight loss clinic, Rozen said. Many of the women in one particular clinic where herbs had been substituted suffered from serious kidney problems. In 2001, the FDA released an alert to consumers and doctors, warning them about the health risks associated with the plant.

Any new cases in the U.S. linked to these plants are more likely caused by long-ago doses or treatment overseas, as most domestic herbalists know about the risks. According to an American herbalist, it's no longer used medicinally in the United States. "There may be the occasional herbalist who uses it, although I don't know of any who do. I wouldn't, and I wouldn't let anyone use it on me. I think most of us just grow it for butterfly larva fodder and because it is an interesting plant," said Gayle Engels, the special projects director for the American Botanical Council (ABC).

"There has been so much guidance provided by the FDA, ABC and the American Herbal Products Association (AHPA), beginning in the 1990s, that I would be surprised if there is even much inadvertent adulteration in the U.S. herbal products industry."

Rozen thinks more education could still help. "I think education is going to be quite important to try and help people avoid this," he said. "And I think it's quite possible. It's quite addictive. It's not like tobacco, and people ingest it deliberately. I think education can go a long way in the case of efforts to avoid exposure to this."

Correction: An earlier version of this story mistakenly said that Rozen called these plants "quite addictive." In fact, he said they are "not addictive."