SAN FRANCISCO, Nov. 3 (UPI) -- Some provocative, though not proof-positive, clues to the autism puzzle are starting to emerge from research investigating differences in children with the disorder.
Among the most compelling results for those who see a link between vaccination and a rise in autism diagnoses, scientists reported up to 80 percent of autistic children are low in glutathione, a key antioxidant for expelling heavy metals from the body.
Glutathione acts as a shield against cellular harm by neutralizing both oxygen-free radicals -- the damaging byproducts of metabolism thought to underlie aging and suspected of contributing to heart disease and cancer -- and toxic metals.
The youngsters' metabolic shortfall came to light in blood tests conducted by a team led by S. Jill James, a former Food and Drug Administration research scientist who now works as a professor of biochemistry and pediatrics at the Arkansas Children's Hospital Research Institute at the University of Arkansas for Medical Science in Little Rock.
The glutathione deficit could leave the children unprotected against toxic substances, and "may contribute to the development and clinical manifestation of regressive autism," one study concluded.
However, the authors cautioned that at this stage they do not know for certain whether the abnormality precedes or proceeds from the disorder.
The discovery may explain why so many autistic children have intestinal problems; glutathione is vital to a healthy gut, the researchers said.
The studies suggest supplements, such as folinic acid and methyl B12, might bring the protective antioxidant back to normal levels, the authors said.
While some anecdotal reports have suggested such treatment may lead to improved mental and social functioning, no conclusive research has determined whether the compounds might extend any benefits to youngsters with autism.
To those who see a link between neurodevelopmental disorders and a mercury-based preservative called thimerosal, once commonly used in childhood shots, James's studies shed a telling light on some other puzzling aspects of autism.
Glutathione levels are naturally lower in males, which could help explain the disproportionately high number of boys affected by the disorder, they said. In addition, the female hormone estrogen is an antioxidant like glutathione, so girls possess a mightier chemical arsenal against metal toxins, they added.
The findings renewed claims that the population-based studies that have provided the preponderance of evidence against a vaccine-autism link have overlooked groups of children susceptible to neurological damage from mercury.
The research not only supports such a connection but also offers a biological explanation for it that could never be gleaned from epidemiology, the thimerosal doubters asserted.
Others, however, said the metabolic defect does not seem to be specific to autism, also making an appearance in children with Down syndrome, among others, raising the possibility the irregularity is a symptom rather than a cause of autism and similar disorders.
In addition, they found fault with the low number of participants -- 55 in one study, 170 in another -- and the failure to account for dietary and behavioral differences that could alter blood chemistry.
The author herself, while acknowledging the findings are suggestive and warrant a follow-up, cautioned against making too much of them.
For example, she thought a press release promoting "Evidence of Harm" (St. Martin's Press, 2005) -- a best-selling book that presents a partial-to-parents portrayal of the autism-vaccine controversy -- overstated the case.
The marketing material, sent to reporters and posted on author David Kirby's Web site, says James's study "is hugely significant in the effort to link mercury exposure to childhood disorders such as autism."
It continues: "(T)he work of Jill James, which shows how a genetically altered metabolism can play a role in blocking the body's ability to excrete heavy metals such as mercury, is 'one more piece of this complicated puzzle that is dovetailing into a workable theory.' The work of Jill James is explained in great detail in 'Evidence of Harm.'"
It goes on: "She found that autistic children cannot properly shed mercury that they received through vaccines, maternal fish consumption, and other sources, because of extremely low levels of sulfur-based proteins, such as glutathione. 'These sulfur-based substances naturally bind with heavy metals to eliminate them from the system,' Kirby says. 'Without them, mercury exposure becomes much more problematic.'"
James commented: "I'm afraid Mr. Kirby is overstating our conclusions -- which did not mention mercury. We simply showed for the first time that children with autism have lower levels of the major intracellular antioxidant, glutathione, which incidentally happens to be the major mechanism for mercury elimination from the body."
"We did not show any genetic data ... Although it may be a logical assumption that children with low glutathione would be less able to excrete mercury, we did not evaluate that in our study, and that possibility was not mentioned," she continued.
"It also must be taken into consideration that our study evaluated children who already have autism, so we do not know whether low glutathione is a cause or consequence at this point," she added. "Our study is provocative but not definitive -- it does warrant further research into the implications of the findings."
Next: Mixed bag of mercury test results
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