Traditional Chinese medicine shop in Hong Kong. Photo by Mailer Diablo.

It’s probably best not to make all your meals out of pink slime and enriched HFCS, but a word to the wise: “Natural” doesn’t always mean safe. A new DNA analysis reveals that traditional Chinese medicine often contains carcinogens and other poisons not listed on the label.

In the herbal preparations, Bunce and his colleagues found members of 68 different plant families, among them plants of the genera Ephedra and Asarum. Both can contain toxic chemicals such as aristolochic acid, a compound banned in many countries because it causes kidney disease and cancer of the upper urinary tract.

Not that the ingredients that are actually on the label are much better, reports Kai Kupferschmidt at ScienceNow.

Some products contained material from animals classified as vulnerable or critically endangered, such as the Asiatic black bear and the Saiga antelope—just as the producers claimed.

The researchers involved believe that these toxins could be a major reason why Taiwan has the highest rates of upper urinary tract cancer in the world.