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Article of Interest - Mercury Toxicity

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Bridges4Kids LogoResearch 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 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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