The consumption of popular Chinese herbal products containing aristolochic acid is associated with an increased risk of urinary tract cancer, a study in Taiwan has found.

Aristolochic acid, known as Mu Tong in Chinese, is found naturally in some herbs that are used in Chinese herbal products to treat hepatitis, urinary tract infection, rhinitis, dysmenorrhea and eczema.

While studies in the past have linked urothelial cancer to the use of aristolochic acid, this is the first study to see if the same association can be made between cancer and herbal products containing aristolochic acid.

In the new study, researchers in Taiwan analysed the medical history of 4,594 patients with urinary tract cancer and compared the findings with those of 174,701 other people without the disease.

In a paper published in the Journal of the National Cancer Institute, the researchers said those who consumed Mu Tong had a far higher risk of developing urinary tract cancer, and the level of risk rose the higher the dosages prescribed.

Led by Jung-Der Wang at the Institute of Occupational Medicine and Industrial Hygiene in National Taiwan University, the researchers called for a ban on products containing Mu Tong.

"In addition to a ban on products that contain any amount of aristolochic acid, we also recommend continued surveillance of herbs or Chinese herbal products that might be adulterated with aristolochic acid-containing herbs," they wrote.

"Finally, patients with a history of aristolochic acid nephropathy or consumption of Mu Tong or Fangchi before they were banned should be monitored regularly for urinary cancer."

The Journal of the National Cancer Institute is published by Oxford University Press.