Human Carcinogenesis and Bracken Fern: A Review of the Evidence

Abstract

The complex taxon embraced in the Pteridium genus, popularly known as bracken fern and notorious weeds in many parts of the world, is one of the few vascular plants known to induce cancer naturally in animals. It has been known for long to be acutely toxic to livestock and sublethal chronic oral feeding of bracken fronds leads to cancerous lesions in the urinary bladder, or bovine enzootic haematuria (BEH) and ileum of cattle. Bracken poisoning has been attributed chiefly to ptaquiloside, a norsesqui-terpene which is also a potent carcinogen inducing various malignancies in laboratory animals. It is capable of alkylating uncoiled DNAbases at key proto-oncogenes of selected organs. Some human populations also eat young bracken shoots and epidemiological studies in Japan and Brazil have shown a close association between bracken consumption and cancers of the upper alimentary tract. In addition, other studies reveal that the mere presence of bracken swards represents a greater risk to die of gastric adenocarcinoma for people who live more than 20 years in such areas or are exposed in childhood. This work reviews the bracken-cancer connections established by in vitro and in vivo experiments and epidemiological studies in various parts of the world, and provides insights into the possible bridges for bracken carcinogens to reach the human diet. Also, specific points where more research is needed are highlighted.

Bovine papillomaviruses, papillomas and cancer in cattle

“…It possesses the structure of an illudane and is quite unstable in mildly acidic or basic conditions, decomposing into an illudane-dienone. Additionally, the ptaquiloside aglycone ptaquilosin is also very unstable and decomposes into the same dienone [3,15]. The dienone has been shown to alkylate DNA via a reactive cyclopropyl ring to form a number of different DNA adducts at N3 of adenines, which can lead to point mutations.…”

“…Metabolites from ptaquiloside and quercetin along with other chemicals from bracken are also found in the blood, urine and milk of cows naturally exposed to bracken and suffering from bladder cancer [15,80]. Exposure to ptaquiloside indirectly through milk from bracken-grazing cows has a big impact on human health, since it has been correlated with human oesophageal and gastric cancer [3,122,139]. In different parts of the world the human consumption of bracken has been linked to GI cancer [2,3,82].…”

“…Exposure to ptaquiloside indirectly through milk from bracken-grazing cows has a big impact on human health, since it has been correlated with human oesophageal and gastric cancer [3,122,139]. In different parts of the world the human consumption of bracken has been linked to GI cancer [2,3,82]. HPV-16 DNA has been found in high percentage in oesophageal cancer particularly in developing countries where the consumption of bracken or milk from bracken fed cows is high [79,84].…”

Immunomodulatory effects ofPteridium aquilinumon natural killer cell activity and select aspects of the cellular immune response of mice

“…Epidemiological studies have revealed a higher risk of certain types of cancers (i.e., esophageal, gastric) in people who consume bracken fern (or its toxins) directly, as in case of crosiers or rhizomes (Sugimura, 2000;Abnet, 2007), or indirectly through consumption of milk from livestock that have fed on the plant (Alonso-Amelot et al, 1996, 1999Alonso-Amelot, 1997;Shahin et al, 1999;Alonso-Amelot and Avendaño, 2002).…”

A biological hazard of our age: Bracken fern [ Pteridium aquilinum (L.) Kuhn] — A Review

“…The usual procedure before eating (cooking in water, in the presence of different chemicals) serves for removing most, but not all, of the carcinogenic activity. In some countries (Japan, Brazil and Venezuela) a close association was found between the consumption of bracken fern and cancers of the upper alimentary tract (Alonso-Amelot and Avendano, 2002). The frequency of oesophageal and gastric cancer is 5.1-8.1 higher in people with a daily bracken intake than in the people not eating this plant (Marliere et al, 1998).…”