Brain toxin found in algae in water
Possible link to Alzheimer's, other ills studied
By Susanne Quick and John Fauber
Milwaukee Journal Sentinel
Posted April 4, 2005
An environmental toxin linked to common neurodegenerative
diseases such as Alzheimer's, Parkinson's disease and
amyotrophic lateral sclerosis has been found in blue-green
algae-contaminated water throughout North America and
The international team of researchers that reported the
finding this week suggested that public health officials
now should consider monitoring for the neurotoxin in waters
that have blue-green algae "blooms," including
water from the Great Lakes and smaller inland waters.
The neurotoxin is called B-N-methylamino-L-alanine, or
"We don't want to be alarmist. This is very preliminary
research," said Paul Allen Cox, lead researcher on
the paper and director of the National Tropical Botanical
Garden, a research institute in Hawaii.
"But gosh, if there is a neurotoxin out there"
it might be prudent to check it out, he said.
The research appears in this week's issue of the Proceedings
of the National Academy of Sciences.
Other researchers agree that the work is interesting
and warrants further investigation. But they, too, caution
it is only suggestive, and no link between blue-green
algae and common neurodegenerative diseases has yet been
"This is certainly very interesting science, and
we're keeping an eye on it. However, its relevance to
Alzheimer's disease has yet to be proven," said William
Thies, vice president for medical and scientific affairs
at the Alzheimer's Association.
The story of Cox and his team's work begins in the early
1900s, when researchers noticed that a large number of
Chamorro people - an indigenous population living in Guam
- were dying of an unusual, paralytic disease that resembled
ALS but had Alzheimer's and Parkinson's disease-like symptoms,
Investigators pointed to a tree called the cycad. Its
seeds, which the Chamorro used for flour, showed trace
levels of BMAA. A strain of cyanobacteria - or blue-green
algae - grows inside cycad roots, where it produces BMAA.
From there, it is transported throughout the plant, including
to the seeds.
But in the 1990s, the theory was discounted. Research
showed that while BMAA can cause neurodegeneration in
monkeys, in order to get toxic effects from cycad flour,
a person would have to eat a heck of a lot of it, Cox
Intrigued, Cox, an ethnobotanist, set out to find out
what was killing these people. He took an expedition to
Guam that was partly funded by Verne and Marion Read,
two Milwaukee-based philanthropists.
Cox knew the Chamorro were eating fruit-eating bats that
foraged on cycad trees. Maybe there was a "DDT effect"
going on there, he thought: bio-magnification of a toxin
through the food chain.
He examined bat tissue and discovered a 10,000-fold increase
in BMAA concentration from seed to bat. This suggested
to him that the Chamorro were unwittingly ingesting high
levels of the neurotoxin.
He then decided to look at brain tissue from Chamorros
who had died of the neurodegenerative disease. To control
for possible baseline levels of the molecule, he examined
15 Canadian brains, too.
What he discovered was shocking: While most of the Canadian
brains showed no sign of the toxin, two had BMAA molecules.
"Where did they get this molecule?" he asked.
What's more, he said, the two BMAA-positive Canadians
had died of Alzheimer's disease - the only two in the
Further investigation revealed similar results: BMAA
was discovered in brain tissue from eight Canadian Alzheimer's
patients, but not in 14 others who had died from causes
other than neurodegeneration. Where were these people
coming into contact with BMAA, Cox wondered. And could
other strains of cyanobacteria carry this neurotoxin?
To find out, he contacted blue-green algae experts around
the globe and asked them to send samples. They complied,
and he received samples from rivers, lakes and oceans.
Of the 30 samples shipped to him, 29 tested positive for
"Holy cow! What's going on?" he wondered. The
neurotoxin appeared to be everywhere he looked.
Wayne Carmichael, professor of aquatic ecology and toxicology
at Wright State University in Dayton, Ohio, is not surprised
Cox found BMAA everywhere.
"Cyanobacterias produce dozens of bioactive properties,"
he said. It's quite possible that if you look, you'll
find other toxins across the board, he said.
He added that what happened in Guam was a unique situation,
and "it does not mean its widespread occurrence is
a general risk to humans. There needs to be a unique set
of circumstances to allow for high enough concentrations."
Others question Cox's link between BMAA and neurodegeneration.
"The data are remarkably thin," said Christopher
Shaw, a professor of ophthalmology and neuroscience at
the University of British Columbia. "They make huge
scientific leaps based on thin data."
Shaw said it's possible that Cox's research is not picking
up BMAA in diseased brains, but rather a similar substance
that is produced in the brain as the result. He noted
that there are a vast number of biochemical abnormalities
in the brains of people with ALS, Parkinson's and Alzheimer's.
In any case, BMAA is an extremely weak neurotoxin, he
However, if Cox is right, he said, his findings will
have to be reproduced by others.
One group of researchers claims to have done that.
Scientists at the University of Miami have been studying
the brains of ALS and Alzheimer's patients from Florida
and other places in the United States.
"We are finding it (BMAA)," said Deborah Mash,
a professor of neurology at the University of Miami and
director of the Brain Endowment Bank. Mash said BMAA has
showed up in all of the brain samples from ALS and Alzheimer's
patients that have been tested by her lab. That research
has not been published yet and the actual number of samples
was not available, she said.
Mash did say, however that only one of 10 brain samples
she examined from patients who did not have brain disease
tested positive for the amino acid, she said. And that
so far, between 40 and 50 brain samples from patients
with brain diseases have tested positive for BMAA among
all the labs that are looking for it worldwide.
However, to definitively establish the link between BMAA
and brain disease, scientists will have to find it in
thousands of samples, she said.
"Here you have this cyanobacteria that's ubiquitous,
that's in lakes, that could be moving up the food chain,"
she said. "Whether or not it's a major environmental
toxin remains to be seen.
"But the story makes sense to me."