A new study [/align] warns that use of certain Chinese herbal products may be linked to increased risk of urinary tract cancer. The study focused on aristolochic acid, a carcinogen found in Chinese herbs such as mu tong (an ingredient in some formulas said to alleviat[align=left]e urinary tract infections).
Researchers analyzed data on 179,295 people, examining the association between use of mu tong and incidence of urinary tract cancer. Study results showed that having been prescribed more than 60 g of mu tong was associated with an increased risk of urinary tract cancer. The increased risk was independent of arsenic exposure (another risk factor for urinary tract cancer).
The study's authors call for a ban on products that contain any amount of aristolochic acid. They also recommend that patients with a history of consumption of mu tong be monitored regularly for urinary cancer.

http://altmedicine.about.com/b/2010/01/0...r-risk.htm

In 2001, the Food and Drug Administration (FDA) issued warnings and an import alert that herbal products are unsafe if they contain or are suspected to contain aristolochic acid.1 A report in the Journal in 2000 described a cohort of 105 patients in whom rapidly progressive nephropathy developed after they had been given an herbal weight-loss product containing aristolochic acid by a Belgian clinic.2 Because of a suspected association between aristolochic acid and urothelial carcinoma, 39 patients with end-stage renal disease underwent prophylactic removal of the kidneys and ureters; urothelial carcinoma was diagnosed in 18 of them. Aristolochic acid nephropathy has been reported in eight other countries, and associated urinary tract cancer has been reported in two.3 The International Agency for Research on Cancer classifies products containing aristolochia species as human carcinogens.4

Despite the actions of the FDA, in 2003 we identified 19 products containing aristolochic acid and 95 products suspected to contain aristolochic acid for sale on the Web. These products and approximately 100 related Web sites are listed on the Web at potency.berkeley.edu/aristolochicacid.html. These herbal products should not be available but are sold on U.S. Web sites for gastrointestinal symptoms, weight loss, cough, and immune stimulation.

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