Across Asia, liver cancer is linked to herbal remedies: study

Researchers have uncovered widespread evidence of a link between traditional Chinese herbal remedies and liver cancer across Asia, a study said on Wednesday.

The findings suggest stronger measures are needed to prevent people from consuming chemicals called aristolochic acids (AA), which are derived from the woody vines of the Aristolochia plant family, said the report in the journal Science Translational Medicine.

The acids can be found in some traditional Chinese medicines that are given during childbirth to prevent parasites and promote healing.

Researchers tested 98 liver tumors that were stored at hospitals in Taiwan, and found that 78 percent contained mutation patterns that indicated the cancers "were likely due to contact with the chemicals", said the study.

Since these acids cause "a well-defined mutational signature", researchers also looked at 89 samples of liver cancer in China, and found that 47 percent showed a link to this traditional medicine component.

In Vietnam, five out of 26 tumors studied were a match (19 percent), along with five out of nine from other countries in Southeast Asia (56 percent).

The link to traditional Chinese medicine was far less common in North America at five percent of 209 liver cancers studied, while in Europe it was just 1.7 percent of the 230 samples looked at.

In 2003, Taiwan banned some herbal preparations made using the plants after it was discovered that AA could cause kidney failure and urinary tract cancers.

However, there is no outright ban in China or Taiwan, and "only specific plants, rather than any plant and product containing AA or its derivatives, are regulated, making it hard for consumers to avoid them," said the report.

Researchers found that the prevalence of AA-associated mutations in liver cancers in Taiwan did not drop after the ban was implemented. 

This could be because it would take more time for a drop in cancers to be noticeable in the data, as was the case with tobacco-related cancers after smoking was revealed to cause lung tumors.

Or it could be that people continue to be exposed to these acids through products and herbal mixtures that still contain them.

In Vietnam, official government data shows up to 80 percent of the 50,000 tons of traditional Chinese medicine consumed each year is low-quality and smuggled into northern provinces from China.

Experts in the field said herbal products with clear origins can help treat certain diseases, but smuggled products with no labels from China will do more harm than good, with clear threats to the liver and kidneys. 

According to police, vendors buy the herbs from smugglers and then turn them into “medicine” using their own recipes. For years, local media has been reporting multiple poisoning cases due to traditional Chinese medicine across Vietnam.