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 Research
Supports Link in Autism to Mercury
by Tina Hesman, St. Louis Post-Dispatch, December 13,
2004
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Children with
autism may process mercury differently than most children,
leaving them susceptible to damage from preservatives in
vaccines and other sources of the heavy metal, according to a
controversial new report released Monday.
The report, by the independent Environmental Working Group,
highlights the research of S. Jill James, a professor of
biochemistry and pediatrics at the University of Arkansas for
Medical Sciences. James conducted blood tests on 20 children
with autism and compared them with blood samples taken from 33
children who do not have autism. She found lower levels of a
mercury-detoxifying chemical, called glutathione, in the blood
of autistic children.
The enzyme also helps rid the body of other heavy metals that
may damage cells and organs.
"Given an equal load of environmental toxicants, these kids
wouldn't be able to detoxify it or excrete it as well as the
average kid," James said.
James also found that supplementing the autistic children's
diets with a combination of folinic acid, betaine and methyl
vitamin B-12 brought glutathione levels back to levels seen in
the children in the control group. The study did not
address whether those changes in metabolism lead to clinical
improvements.
But a pediatrician at the University of Virginia, Dr. Elizabeth
A. Mumper, says children she treated with the supplements got
better. The results of Mumper's study are not yet published.
The studies again raise concerns that some genetically
susceptible children are more prone to neurological damage when
exposed to mercury and other toxins in the environment.
Vaccines, fish and dental amalgam fillings have been fingered as
sources of mercury.
The vaccine connection to the disorder has been the subject of
intense debate. Parents and some scientists say that the use of
a mercury-based preservative, called thimerosal, in vaccines
corresponded with an explosion in the number of autism cases.
Autism is estimated to affect about 60 of every 10,000 children
in the United States. That rate is about 10 times that of 1980.
Some experts say the difference may be due to better diagnosis,
but other groups say increased awareness does not account for
the massive increase. Thimerosal was taken out of vaccines in
2002, but the rate of autism remains at the same level as before
it was removed. Many scientists say the prestigious
Institute of Medicine, associated with the National Academies of
Science, definitively severed the purported link between vaccine
preservatives and autism in a review earlier this year. The
preservative has been phased out of childhood vaccines, although
some flu shots still contain thimerosal.
But parent groups continued to insist that population-based
studies, known as epidemiological studies, overlooked groups of
children with genetic susceptibility to neurological damage from
mercury. The new research supports a link between mercury and
autism and offers a biological explanation for the connection
that numbers could never achieve, some parents and activists
say.
"As a mother, I can tell you I'd much rather talk to a scientist
who spends their life in front of a microscope than a
statistician who talks to me with Excel spreadsheets and a
calculator. I want to see the hard clinical evidence," said
Lujene G. Clark, co-founder of the Web site
www.NoMercury.org. Clark
and her husband, Dr. Alan Clark, started the Web site after
their son was diagnosed with Asperger's syndrome, one of a
spectrum of autism disorders. The Clarks say a flu shot with the
mercury-base preservative thimerosal caused their son's
disorder.
The Environmental Working Group admits that James' study does
not establish mercury as a cause of autism but recommends that
the metabolic test be used in further epidemiological studies to
see if children with lower levels of glutathione are indeed more
likely to develop the disorder. The group also called for more
stringent limits on environmental contaminants to protect the
most vulnerable children. The Environmental Working Group is a
nonprofit, nonpartisan organization that receives the bulk of
its funding from private charities.
Some scientists say the study is intriguing but is unlikely to
reopen an investigation of a link between vaccines and autism.
"Any study that shows a difference between autistics and
controls is of great interest and worth pursuing," said Dr. John
Constantino, a professor of psychiatry and pediatrics at
Washington University.
But the metabolic defect James discovered does not appear to be
specific to autism, he noted. Children with Down syndrome also
had lower levels of the metal-detoxifying enzymes. That could
mean that the difference is a symptom of autism and other
neurological disorders rather than a cause, Constantino said.
"It's still interesting, even if it's only an effect of autism,"
he said.
Even if single exposures to mercury in vaccines leads to autism,
it is doubtful that dietary changes could reverse damage to
brain cells, Constantino said. Other dietary remedies for
autism, including Vitamin B6 and secretin, have failed to stand
up to scientific scrutiny, he said.
Study is criticized
Autism is widely regarded as a genetic disorder, probably caused
by defects in multiple genes. Researchers at Washington
University and elsewhere have located several stretches of DNA
likely to contain autism-related genes but do not yet know which
genes are responsible for the disorder. James said she had
preliminary data suggesting that defects in several genes
involved in making glutathione may be linked to autism. Results
of those studies are expected to appear early next year.
Parents are quick to assign blame for autism to environmental
factors despite a lack of evidence, said Dr. Paul Offitt, a
pediatrician and vaccine expert at Children's Hospital of
Philadelphia.
"Medicine has many weaknesses, and one of them is that we don't
know what causes everything," said Offitt. "It may be that
thimerosal causes harm. I haven't seen one shred of evidence to
support it."
Offitt called the study "weak" and expressed concern that it
offered false hope to parents desperately searching for a cure
for their children's autism. The study involved a small number
of autistic children and failed to account for dietary and
behavioral differences that could lead to changes in blood
chemistry, he said.
The Clarks already give their son dietary supplements, said
Lujene Clark. She said she doesn't need further proof that the
remedy is a success.
"I don't need to see any additional clinical data. I live with
9-year-old living proof that methyl B-12 works. I'm sitting here
with my son's report card, and he is tremendously better."
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