Friday, January 21, 2011

It kills the Maori of New Zealand

Its beauty is deceptive and treacherous, as its innocent appearance hides fern highly carcinogenic substances, which cause various cancers in both animals and humans. I am speaking of Pteridium aquilinum, a fern of the family Hypolepidaceae widely distributed throughout the world, except Antarctica. In the genus Pteridium stands a single species: aquilinum, two subspecies: aquilinum and caudatum and twelve varieties.
Vigorous new fronds in a copy of Pteridium aquilinum on the beach in Los Cancajos of the Canary island of La Palma in May.

The Maori of New Zealand cultivated this fern for its rhizomes, from which they obtain a flour to make bread to feed it. Carcinogenic substances from the rhizomes are responsible for the high rate of gastric cancer among these natives of up to two and a half times higher than the rest of the New Zealand population.

 Pteridium aquilinum growing in the mountains at about 1000 m in the Pla de Cuber of the Serra de Tramuntana in Mallorca Island in the middle of July.               
In Venezuela and Costa Rica, where the fern grows into large pasture in the highlands, there called "potreros" cattle feed on the fronds, which are carcinogens that cause the disease called Bovine enzootic hematuria, commonly known as "orinadera de sangre", guilty of the death of a large number of cows, oxen and breeding bulls, in which causes bone marrow depression with leukopenia, thrombocytopenia and severe anemia, exacerbated by bladder tumors that bleed profusely. It also produces cancer in bladder of water buffaloes  and in the intestine and bladder of the sheep that graze on these pastures invaded by the fern, which behaves as an invasive plant and shifts the normal vegetation.

The Bovine enzootic hematuria has been observed in numerous countries as diverse as New Zealand, Brazil, Sweden, England, Canada and Fiji, although the most affected Venezuela and Costa Rica.

Humans who consume contaminated milk from cows that feed on the fronds of Pteridium aquilinum have a high rate of stomach cancer, much higher than expected in any human population. Costa Rica ranks third worldwide in incidence and mortality from stomach cancer. The carcinogenic substances found in milk are shikimic acid, quercetin, aquilide A and above all ptaquiloside, which is considered the main toxic principle and is in highest concentration in the tender fronds. Was isolated in 1983 and its carcinogenic toxicity  in laboratory animals such as rats, mice, quail, dogs, hamsters, etc. .. , in which causes malignant  neoplasm of bowel, bladder, lung and lymphatic leukemia, was shown in 1984. It was also demonstrated experimentally the toxicity in cattle. When ingested is broken down into a chemical  second derivative called dienone, which is the real toxic and cause direct damage to DNA and activation of oncogenes. 

Cows graze in pastures where it not grows Pteridium aquilinum not have the hematuric disease and their milk is free from carcinogenic pollutants, which affects the health of humans who feed on their milk, which present a very low rate gastric cancer, similar to that expected in any human population.

Grassland invaded by Pteridium aquilinum in a clearing in the Sierra de Grazalema Natural Park in the Cadiz province in mid-May.

The Pteridium aquilinum also contains large amounts of the enzyme thiaminase which destroys thiamine or vitamin B1, causing a severe vitamin deficiency similar to beriberi, with motor incoordination, paralysis and seizures, even to cause death by motor suffocation if they have consumed large amounts of fern. This issue primarily affects non ruminant animals such as pigs, horses, mules and donkeys, not affecting ruminants for the large amounts of thiamin synthesized by the ruminal flora.

Copy of Pteridium aquilinum in an oak of Natural Park of Los Alcornocales in the province of Cadiz.

In the sheep causes progressive blindness due to degeneration of the retina and cerebrocortical necrosis, dying of starvation by not being able to drink or feed or follow the herd on the move.

      Pteridium aquilinum sprouting in early May on the outskirts of the city of Horta on Faial Island in the Azores Archipelago

In Japan, where it is customary in some areas to feed on the tender fronds of Pteridium aquilinum, found a clear relationship between consumption and the incidence of cancer of the esophagus and stomach. In these regions is considered a vegetable and is called Warabi. You can see it on sale in markets. Families out for a walk in the field are used to collect the tender fronds of this fern, for cooking later in their homes.
 Pteridium aquilinum growing as an epiphyte on the trunk of a Canary date palm, Phoenix canariensis, in the city of Barlovento of La Palma Island.

In Brazil, in areas where abundant, its tender fronds are also eaten as vegetables and is studying the clear relationship between their consumption and the high incidence of stomach and esophageal cancer.

        Underside of a frond of Pteridium aquilinum with mature sori.    

Studies in Asia have noted that the tender fronds cooking at high temperatures in traditional woks neutralizes carcinogens, and can be safely consumed. Just not suitable for consumption raw or lightly cooking. However, these assertions are contradicted by the high rate of cancer of the Maori eating bread made with flour from rhizomes, logically high temperature ovens.

The sori are covered on the outside by a pseudoindusium formed by the revolute margins of the pinna and on the inside by a true indusium brown membranaceous and fimbriate edge.
Some studies also suggest that the simple inhalation of spores can cause lung cancer, but has not been demonstrated.

In Wales, western England, where it grows in abundance Pteridium aquilinum, there has been an unusual incidence of cancer among the human population. Not being consumed as food, has blamed the contamination of well water exudative fern root and the incorporation of spores into the water in surface water systems, but has not been demonstrated any relationship.

A deep-rooted custom is padded with fronds of Pteridium aquilinum boxes with fresh oysters. In this case perhaps the danger is contamination with spores of the fern open oysters and placed on the fronds.

In countries where this fern behaves as an invasive weed, crowding out the normal grass, are studying various methods of eradication, which to date have been too costly and ineffective.

And finally in the air is a question: why such toxicity?. The answer could perhaps be the same as for the tiny poison frogs of the Amazon forests: the fern Pteridium aquilinum funnels large amounts of toxic substances in their tissues simply not be eaten, to protect itself, to eliminate by a slow and cruel form its predators, ultimately, to survive and  in the light of the results, their strategy has not done anything wrong. 

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