The toxicity and pathology of selected dietary herbal medicines.
Toxicity studies were conducted by the National Toxicology Program (NTP) to provide information on the potential for toxicity from long-term use of commonly used herbal medicines. Here, we review the findings from these NTP toxicology/carcinogenesis 2-year rodent studies of 7 commonly used herbs. In these studies, the individual herb or herbal product was administered to F344/N rats and B6C3F1 mice by oral administration for up to 2 years. The spectrum of carcinogenic responses ranged from no or equivocal evidence for carcinogenic activity (ginseng, milk thistle, and turmeric oleoresin) to a liver tumor response (ginkgo, goldenseal, kava), thyroid tumor response (ginkgo), or an intestinal tumor response (Aloe vera whole leaf nondecolorized extract). Different mechanisms may be involved in the occurrence of liver (ginkgo, goldenseal, and kava kava) and gastrointestinal toxicity (turmeric oleoresin and Aloe vera whole leaf nondecolorized extract), while the toxic lesion is the same. The results from these hazard identification toxicity/carcinogenesis studies along with those from ongoing National Institute of Health clinical trials of herbal medicines provide more complete information on the risks and benefits from herbal medicine use in the general population.