Induction of tumors in rats by bracken fern (Pteridium aquilinum) from Ouro Preto (Minas Gerais, Brazil).

1. The possible carcinogenicity of bracken fern (Pteridium aquilinum, common name: "Broto de Samambaia") which is used as food by the population of Ouro Preto (Minas Gerais, Brazil) and neighboring areas, was studied in rats. 2. Fifteen (6 female and 9 male) 45-day old Wistar rats were fed a diet containing dried bracken fern (5%, w/w) for up to 70 weeks. After death or sacrifice, the animals were carefully examined for tumors in the gastrointestinal tract, bladder, lungs, liver, and kidneys. 3. All experimental animals showed gastrointestinal tract tumors which were located mainly in the ileum. Most of the tumors were malignant lesions (adenocarcinomas and sarcomas), although benign adenomas were also present. One animal developed a lymphoma and none showed vesical tumors. 4. No tumors were detected in 11 control rats (5 female and 6 male). 5. These data clearly demonstrate that Pteridium aquilinum is carcinogenic for rats.