Written by Joyce Elizabeth Mauk, MD
Advisory Board Member, Association for Science in Autism Treatment
President/CEO and Medical Director Child Study Center, Fort Worth, Texas
One of the unfortunate byproducts of the media hype relating autism to vaccines is renewed interest in chelation as a treatment for autism. Chelation refers to a medical procedure that uses chemicals to remove heavy metals from the bodies of children with autism. The agents most commonly used are Calcium Disodium ethylenediamine-tetraacetic acid (Ca-EDTA), Dimercaptosuccinic acid (DMSA) and 2-3-dimercaptopropane-1-sulfonate (DMPS). These man-made molecules all have a high affinity to bond metals and remove them from the body via urine when the drug itself is excreted. In addition to these more traditional chelation agents, I have found Internet references to the use of the herb cilantro and certain types of clay for chelation.
The administration of metal-binding molecules to treat autism is based on speculation that mercury poisoning (via administration through immunization, mercury-containing dental fillings or environmental exposure) causes autism. Therefore, the rationale is that removing the toxic metal will cure the autism or lead to an amelioration in the symptoms of autism.
It is important to note that chelation has some legitimate uses. In particular, it is indicated for removing lead from children with severe lead poisoning, and many papers in the medical literature confirm its efficacy for this purpose. Of note, however, chelation is also an unproven, but widely-prescribed treatment for atherosclerosis. There are also industrial uses for these chemicals.
Determining whether or not chelation is an appropriate treatment for autism is predicated on chelation proponents obtaining and publishing high-quality scientific evidence to support their assertions. Medical scientific evidence is published in legitimate peer-reviewed scientific publications. Scientists submit publications with a hypothesis to test and present their evidence to prove or disprove it. Editors have experts in the field review papers and decide if they are appropriate for publication. This process can lead to delays in making new scientific information available to the public or treating physicians, but there are many safeguards in this process. There is also a hierarchy of quality of scientific studies with case reports, testimonials and expert opinion being at the lowest level of quality and with randomized case-control studies with high numbers of participants as the highest. Also, good scientific studies have clear outcome measures (for example a decrease in the counts of abnormal behavior, an increase in skills learned, etc) as opposed to reporting a subject being generally “better”. They control for other competing variables, i.e. no change in medication, diet, or therapeutic intervention during the course of the study. Also the evaluators of outcomes should be “blind” to the treatment condition, not knowing if the child has received the active agent (chelator) or not.
Whether or not exposure to heavy metals causes autism requires conducting careful studies to identify patterns that would suggest causality such as a temporal association of cause and effect (e.g., whether mercury exposure is followed immediately by signs of autism), a plausible biologic mechanism, and a dose response relationship (e.g., whether higher levels of mercury exposure increase the risk of autism). Existing scientific evidence does not support mercury as a cause of autism, and suggests instead that a number of genetic variations are most likely responsible for the condition.
Typically, physicians who prescribe chelation will test baseline levels of heavy metals in the urine of patients and then test the urine again after the administration of the chelation drug. However, this may not be a valid assessment. One published report of a child with environmental mercury toxicity (presenting with acrodynia, or burning pain associated with mercury toxicity) showed that urinary level did not reflect clinical improvement after chelation. Another study of children with autism concluded that since DMSA chelation did not lead to high excreted levels of mercury, the children with autism did not have a high body burden of the metal.
A recent search of the scientific literature via Medline found no randomized controlled trials of the use of chelation for the treatment of autism. A proposed study that was to be funded by the NIMH was canceled. Several papers outlining only the opinion of the authors (listed as “pre-pilot”) advocate a role for chelation as a treatment for autism based on personal experience.
Individuals or parents making decisions about introducing a drug intervention such as chelation must weigh risks to benefits. There are no known scientifically-validated benefits of the administration of chelating agents, yet there are some reported risks. Known side effects of these chemicals include: Two reported deaths (presumably from hypocalcemia induced by using an incorrect drug administered too quickly); hypocalcemia; and depletion of beneficial metals (zinc, iron). Ten percent of DMSA-treated patients show evidence of gastrointestinal issues including elevation in liver enzymes. In short, there is not enough scientific evidence available at this time to advocate a role for chelation of heavy metals in the treatment of autism, and there is potential for adverse side effects.
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Citation for this article:
Mauk, E. J. (2009). Chelation treatment for children with autism. Science in Autism Treatment, 6(1), 7, 14.