DNC News

Autism: another piece in the puzzle

Jacob Schor, ND

June 1, 2006


Subject: New evidence suggests that inability to detoxify heavy metals plays a role in autism.



About this time last year I sent out a newsletter reviewing recent developments in the understanding of autism. A study published in April, 2005 suggested that children who develop autism have a genetic trait which lowers their ability to inactivate toxic substances in their bodies. They were more susceptible to injury from toxic exposures.





A new study reported on in the May 30, 2006 issue of New Scientist takes this a step further.

The magazine reports that urine samples from French children show a link between autism and heavy metals and dangle the possibility that the drugs used to treat heavy metal poisoning might be useful in treating autism. [i]


The sample obtained from autistic children contained high levels of chemicals called porphyrins which are precursors to hemoglobin. Heavy metals block hemoglobin production causing higher than expected amounts of porphyrin to accumulate and show up in the urine. The concentrations of one molecule, coproporphyrin, were 2.6 times higher in autistic children as in controls.


That autism is linked isn't a totally new idea of course. An ongoing debate has raged for years over the idea that autism is triggered by the mercury used as a preservative in vaccinations. A hypothesis proposed in October, 2005 suggested that the mercury in the vaccines, although a small quantity, was enough to inhibit the action of the enzyme methionine synthetase in genetically susceptible individuals enough to cause changes in brain development. [ii]


The International Journal of Toxicology reported in 2003 that infants with autism had difficulty excreting mercury compared to other children. Researchers had compared mercury levels in hair samples from healthy and autistic children and found almost seven times the amount of mercury was being excreted by the healthy kids. [iii]


The recent New Scientist article says that normal porphyrin levels can be restored through chelation in the autistic children but does not report whether it affected their mental function. In recent years a good number of anecdotal reports have circulated regarding the benefit of heavy metal chelation therapy for autistic children yet I have not yet seen a well controlled study of this therapy published. Given the current theories and data though we should expect such a study in the near future.




[i] http://www.newscientist.com/channel/health/mg19025535.400.html


Neuro Endocrinol Lett. 2005 Oct;26(5):439-46.

Related Articles, Links

Mercury and autism: accelerating evidence?

Mutter J , Naumann J , Schneider R , Walach H , Haley B .

Institute for Environmental Medicine and Hospital Epidemiology, University Hospital Freiburg , Germany . joachim.mutter@uniklinik-freiburg.de

The causes of autism and neurodevelopmental disorders are unknown. Genetic and environmental risk factors seem to be involved. Because of an observed increase in autism in the last decades, which parallels cumulative mercury exposure, it was proposed that autism may be in part caused by mercury. We review the evidence for this proposal. Several epidemiological studies failed to find a correlation between mercury exposure through thimerosal, a preservative used in vaccines, and the risk of autism. Recently, it was found that autistic children had a higher mercury exposure during pregnancy due to maternal dental amalgam and thimerosal-containing immunoglobulin shots. It was hypothesized that children with autism have a decreased detoxification capacity due to genetic polymorphism. In vitro, mercury and thimerosal in levels found several days after vaccination inhibit methionine synthetase (MS) by 50%. Normal function of MS is crucial in biochemical steps necessary for brain development, attention and production of glutathione, an important antioxidative and detoxifying agent. Repetitive doses of thimerosal leads to neurobehavioral deteriorations in autoimmune susceptible mice, increased oxidative stress and decreased intracellular levels of glutathione in vitro. Subsequently, autistic children have significantly decreased level of reduced glutathione. Promising treatments of autism involve detoxification of mercury, and supplementation of deficient metabolites.



Int J Toxicol. 2003 Jul-Aug;22(4):277-85.

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Reduced levels of mercury in first baby haircuts of autistic children.

Holmes AS , Blaxill MF , Haley BE .

SafeMinds, Cambridge , Massachusetts , USA .

Reported rates of autism have increased sharply in the United States and the United Kingdom . One possible factor underlying these increases is increased exposure to mercury through thimerosal-containing vaccines, but vaccine exposures need to be evaluated in the context of cumulative exposures during gestation and early infancy. Differential rates of postnatal mercury elimination may explain why similar gestational and infant exposures produce variable neurological effects. First baby haircut samples were obtained from 94 children diagnosed with autism using Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM IV) criteria and 45 age- and gender-matched controls. Information on diet, dental amalgam fillings, vaccine history, Rho D immunoglobulin administration, and autism symptom severity was collected through a maternal survey questionnaire and clinical observation. Hair mercury levels in the autistic group were 0.47 ppm versus 3.63 ppm in controls, a significant difference. The mothers in the autistic group had significantly higher levels of mercury exposure through Rho D immunoglobulin injections and amalgam fillings than control mothers. Within the autistic group, hair mercury levels varied significantly across mildly, moderately, and severely autistic children, with mean group levels of 0.79, 0.46, and 0.21 ppm, respectively. Hair mercury levels among controls were significantly correlated with the number of the mothers' amalgam fillings and their fish consumption as well as exposure to mercury through childhood vaccines, correlations that were absent in the autistic group. Hair excretion patterns among autistic infants were significantly reduced relative to control. These data cast doubt on the efficacy of traditional hair analysis as a measure of total mercury exposure in a subset of the population. In light of the biological plausibility of mercury's role in neurodevelopmental disorders, the present study provides further insight into one possible mechanism by which early mercury exposures could increase the risk of autism.

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