- A potent toxin produced by common algae has been found
in the brains of nine Canadians who died of Alzheimer's disease.
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- The same neurotoxin has turned up in brain tissues taken
from people in Guam who died of dementia, say researchers, who warn that
chronic exposure to the algal toxins may pose a public health threat.
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- It "may now be prudent" to monitor drinking
water and food for the toxin known as BMAA, short for beta-n-methylamino-L-alanine,
an international team reports in the Proceedings of the National Academic
of Sciences this month.
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- BMAA is produced by cyanobacteria, ubiquitous algae common
to lakes, oceans and the soil, and can build up in the food chain.
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- A Canadian dementia specialist stresses the evidence
linking the toxin to Alzheimer's disease is circumstantial. But he says
it is "intriguing" and warrants followup.
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- "It's a red flag, an alert, that we've got to look
into," says Dr. Jack Diamond, scientific director of the Alzheimer
Society of Canada.
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- He stresses that many risk factors are linked to the
mind-destroying disease, and more study is needed to prove BMAA is one
of them.
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- The international team, headed by Paul Cox of the Institute
for Ethnomedicine in Hawaii, reports "BMAA was recently discovered
in the brain tissues of nine Canadian Alzheimer's patients." The toxin
was not detected in 14 other Canadians who died of causes unrelated to
neurodegeneration.
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- Dr. Patrick McGeer at the University of B.C. is reported
to have supplied the Canadian brain samples. McGeer is travelling and could
not be reach for comment.
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- "Cyanobacteria might be the ultimate source of the
BMAA in the Canadian Alzheimer's patients," Cox and his colleagues
suggest in their paper. The team has shown that BMAA is produced by many
species of cyanobacteria around the world.
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- It has long been known cyanobacteria pose health hazards.
Drinking water heavily contaminated with the organisms has led to hospitalizations
and in some cases death.
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- Cox and his colleagues believe the BMAA produced by the
algae may also act as a "slow toxin." They chemical can be bound
by proteins, and gradually released over many years.
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- They have shown BMAA, from soil-dwelling cyanobacteria,
concentrate in plants and flying bats in Guam. The bats are a traditional
delicacy of the indigenous Chamorro people, who suffer a high rate of a
dementia-related disorders. BMAA has been found in the brains of affected
individuals, leading Cox to suggest "Chamorros may unwittingly ingest
high levels of BMAA in their traditional diet."
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- BMAA's chemical signature in the brains of Canadian Alzheimer's
patients indicates the problem may not be unique to Guam.
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- Diamond says the sample size of nine Alzheimer's patients
is far too small and a well-controlled study looking at elderly people
with and without Alzheimer's is needed to establish a link. "It's
an epidemiology study that's needed at this stage," he says. "A
big one."
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- Health Canada scientists are aware of the report and
are tracking the scientific literature, says Christopher Williams, one
of the department's media relations officers. He says there no plan at
this stage to launch a followup study.
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- Cox's team argues the possible health consequences of
chronic exposure to low levels of BMAA deserve more attention.
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- "It may now be prudent to monitor BMAA concentrations
in drinking waters contaminated by cyanobacterial blooms," they say.
They also advise checking for BMAA in fish and animals that may be ingesting
the microbes.
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- © The Vancouver Sun 2005
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- http://www.canada.com/vancouver/
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