Bracken as a risk factor in digestive tract tumors: state of the art

The present knowledge of the risks of exposure to bracken fern (Pteridium aquilinum) is presented. The history of research on bracken toxicity is reviewed, covering the animal observations and chemical analysis, and focusing on the carcinogenic effects in various animal species and on the nature and biological properties of the known carcinogens. The implications of human exposure to bracken are inferred, the possible ways of contamination are discussed, and the existing epidemiological studies are commented. Bracken contribution to digestive tract tumors is deduced, and the need of further research on the plant toxicity and detailed epidemiological investigations with the exposed population is stressed.