A Chinese herb that caused kidney failure in more than 100 people also causes kidney cancer, according to researchers at The Free University of Brussels and elsewhere. As of June, the herb was still being sold in the U.S.

Joelle Nortier and colleagues found cancer in 18 of 39 Belgians who had been diagnosed with end-stage kidney failure caused by the Chinese herb Aristolochia fangchi. All but two of the other 21 people had precancerous lesions.

The patients had all taken weight-reducing pills containing powdered Chinese herbs between 1990 and 1992. The manufacturer inadvertently replaced one of the herbs, Stephania tetrandra, with Aristolochia fangchi, which has a similar-sounding Chinese name. It contains aristolochic acid, which is toxic to kidneys and carcinogenic in animal studies.

"The 1994 Dietary Supplement Act does not require that dietary supplements...be shown to be safe or effective before they are marketed," wrote David A. Kessler, former Commissioner of the Food and Drug Administration, in an editorial that was published with the study.

Congress allows the FDA to act if a supplement poses a "significant and unreasonable risk," noted Kessler, but "the burden of proof lies with the FDA. Even when the agency is able to act, how is it supposed to know which products contain aristolochic acid, and who sells them?" he asked. "Congress has put the FDA in the position of being able to act only after the fact and after substantial harm has already occurred."

New Eng. J. Med. 342:1686, 1742, 2000.

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