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• Comfrey is a source of pyrrolizidine alkaloids that present a serious health hazard to consumers when they are ingested.
• Comfrey contains pyrrolizidine alkaloids, substances that are firmly established to be hepatotoxins in animals.
• Reports in the scientific literature clearly associate oral exposure of comfrey and pyrrolizidine alkaloids with the occurrence of veno-occlusive disease (VOD) in animals. Moreover, outbreaks of hepatic VOD have been reported in other countries over the years and the toxicity of these substances in humans is generally accepted.
• Although information is generally lacking to establish a cause-effect relationship between comfrey ingestion and observed adverse effects humans, the adverse effects that have been seen are entirely consistent with the known effects of comfrey ingestion that have been described in the scientific literature.
• The pyrrolizidine alkaloids that are present in comfrey, in addition to being potent hepatotoxins, have been shown to be toxic to other tissues as well.
• There also is evidence that implicates these substances as carcinogens.
• Manufacturers bear the primary responsibility for ensuring that their dietary supplement products are safe. The agency strongly recommends that firms marketing a product contains comfrey or another source of pyrrolizidine alkaloids remove the product from their market and alert their customers to immediately stop using the product.
• The FDA also believes that manufacturers need to take adequate steps to identify and report adverse events, especially adverse events that may include liver disorders, associated with any product that contains an ingredient known to contain pyrrolizidine alkaloids.
* The letter was sent to: American Botanical Council, American Herbal Products Association, Council for Responsible Nutrition, Consumer Healthcare Products Association, National Nutritional Foods Association, Utah Natural Products Alliance, American Association of Oriental Medicine, and the American College of Acupuncturists and Traditional Medicine.
Source: U.S. Food and Drug Administration, Rockville, MD.