Basis for heavy metal detoxification in autistic children
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Is there a need for heavy metal detoxification?
Recently, some autism websites and discussion forums have been quoting a new study published by Soden et al that there are “no heavy metals to be chelated” out of autistic children.
We review the claims here. First, here's an abstract from the study on chelation for heavy metal detoxification:
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Soden SE, Lowry JA, Garrison CB, Wasserman GS.
Section of Behavioral and Developmental Sciences, Children's Mercy Hospital and Assistant Professor of Pediatrics, University of Missouri - Kansas City School of Medicine. Kansas City, Missouri. USA
Clinical Toxicology (Phila) 2007;45(5):476-81.
Introduction. The complementary and alternative medicine practice of prescribing chelators to children with autism is based on the premise that the chronic symptoms of autism can be ameliorated by reducing heavy metal body burden.
However, there has not been definitive evidence, published to date, to support the assertion that children with autism are at increased risk of an excess chelatable body burden of heavy metals.
The oral chelator meso-2,3-dimercaptosuccinic acid (DMSA) can be used diagnostically to mobilize heavy metals from extravascular pools, enhancing the identification of individuals who have a chelatable body burden.
Methods. Seventeen children with autism and five typically developing children were enrolled in a pilot study to test for chelatable body burden of Arsenic (As), Cadmium (Cd), Lead (Pb), and Mercury (Hg).
Evaluation included a questionnaire regarding potential exposure to heavy metals, diet restrictions, a baseline 24-hour urine collection, and a DMSA-provoked urine collection.
Urine collections were sent for As, Cd, Pb, and Hg quantification by Inductively Coupled Plasma-Mass Spectrometry. Unprovoked reference ranges were used in the interpretation of all collections.
Results. Fifteen autistic children and four typically developing children completed the study.
Three autistic subjects excreted one metal in greater quantity during the provoked excretion than baseline.
Two of these were very close to the limit of detection. In the third case, the provoked excretion of mercury was between the upper limit of normal and lower limit of the potentially toxic reference range.
Fish was removed from this child's diet for greater than one month, and the provoked excretion test repeated. The repeat excretion of mercury was within the normal range.
Conclusion. In the absence a proven novel mode of heavy metal toxicity, the proportion of autistic participants in this study whose DMSA provoked excretion results demonstrate an excess chelatable body burden of As, Cd, Pb, or Hg is zero. The confidence interval for this proportion is 0-22%.
Layman’s summary of the study on heavy metal detoxification
Sogen and team (the Soden Study) gave oral DMSA (a chelating drug for heavy metal detoxification) to a group of 15 autistic children and four normal children. The children were given the drug three times over a period of 16 hours.
The researchers measured urine samples before and after all the children (autistic and non-autistic) were given the drug. They found that there were no heavy metals in the urine of normal children
In the case of the autistic children, the study found that two of them had some traces of arsenic and cadmium in their urine before they took the drug. After the drug was given, the researchers found traces of arsenic, cadmium, lead and mercury in five of the children. But these amounts were not considered significant.
Thus, the study concluded that autistic children did not need heavy metal detoxification because they did not have heavy metals in their body that could be chelated with DMSA.
A different study on heavy metal detoxification
However, another scientific study on heavy metal detoxification, published in a peer-reviewed medical journal, came to an entirely different conclusion. In this study, autistic children excreted significantly more mercury than normal children when given the same drug DMSA.
Below is an abstract from this study on heavy metal detoxification:
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Jeff Bradstreet, M.D. DavidA. Geier, B.A. Jerold J. Kartzinel, M.D. James B.Adams, Ph.D. MarkR. Geier, M.D., Ph.D.
Journal of American Physicians and Surgeons Volume 8 Number 3 Fall 2003
ABSTRACT
Large autism epidemics have recently been reported in the United States and the United Kingdom. Emerging epidemiologic evidence and biologic plausibility suggest an association between autistic spectrum disorders and mercury exposure.
This study compares mercury excretion after a three-day treatment with an oral chelating agent, meso-2,3- dimercaptosuccinic acid (DMSA), in children with autistic spectrum disorders and a matched control population.
Overall, urinary mercury concentrations were significantly higher in 221 children with autistic spectrum disorders than in 18 normal controls (Relative Increase (RI)=3.15; P < 0.0002).
Additionally, vaccinated cases showed a significantly higher urinary mercury concentration than did vaccinated controls (RI=5.94; P < 0.005). Similar urinary mercury concentrations were observed among matched vaccinated and unvaccinated controls, and no association was found between urinary cadmium or lead concentrations and autistic spectrum disorders.
The observed urinary concentrations of mercury could plausibly have resulted from thimerosal in childhood vaccines, although other environmental sources and thimerosal in Rh (D) immune globulin administered to mothers may be contributory.
Regardless of the mechanism by which children with autistic spectrum disorders have high urinary mercury concentrations, the DMSA treatment described in this study might be useful to diagnose their present burden of mercury.
You can read the full article on this heavy metal detoxification study at: http://www.jpands.org/vol8no3/geier.pdf
Layman’s summary
Bradstreet and team (the Bradstreet Study) gave DMSA to a group of 221 autistic children and 18 normal children. They compared the urine of the two groups after nine doses of DMSA given over three days.
The study found that the autistic group excreted much more mercury than the normal children. Although the autistic group also excreted more cadmium and lead, the difference was not big enough to be considered significant.
Discussion on heavy metal detoxification
To form an opinion about the relative merits of the two studies, let us look at the differences in design and methods.
| Sogen study | Bradstreet study | |
| Number of cases | 15 | 221 |
| Number of controls | 4 | 18 |
| Doses of DMSA | 3 doses over one day | 9 doses over 3 days |
| Urine collection | 24 hours urine | 1 sample after 9th dose |
| Unit measure of heavy metals | total micrograms over 24 hours | micrograms per gram of creatinine |
| Measure of outcome* | baseline to post | autistic vs normal |
Remarks about measure of outcome:
It was meaningless for the Soden Study to measure autistic vs normal.
Bradstreet Study did not take baseline as it was a retrospective study.
It appears that the Soden Study could not find any significant traces of heavy metals in most of the children tested (both autistic and non-autistic) after administration of DMSA. In this study, urine collection started immediate after the 1st dose of DMSA.
Clinical experience with heavy metal detoxification
However, our clinical experience shows that when autistic children are given diagnostic doses of oral DMSA, the 6-hour urine typically contain measurable amounts of heavy metals like lead, mercury and arsenic. We typically start urine collection after the final dose of DMSA. This is similar to the Bradstreet Study.
This one difference in study design may be the most plausible reason for the difference in trial results. The Soden Study found nothing much in the urine of the children even after 3 doses of DMSA over 16 hours.
The researchers had justified dosing over one day rather than three days by citing data from acute heavy metal poisoning treatment. However, autistic children do not have acute heavy metal poisoning. They are more likely to have low-dose chronic mercury poisoning which could be tightly bound to deep body tissues. A three-day dosing protocol might therefore have been more appropriate.
Another point to consider is that the Bradstreet Study has more statistical power arising from the larger population of 239 subjects vs 19 subjects in the Soden Study.
Further, the Soden Study had stated their scientific hypotheses in a rather curious way: “In the pilot study the DMSA provoked excretion test is used to challenge the assertion (highlight by author) that a substantial proportion of autistic children have an excess chelatable body burden of heavy metals.”
From the language used, it appears that the researchers had a bias against the use of chelators in autistic children and had set out to debunk the practice of heavy metal detoxification.
In contrast, the Bradstreet Study stated their null hypothesis as: “Our null hypothesis was that the populations under study (Authors’ note: i.e. autistic vs non-autistic children) should have similar distribution of excreted heavy metals”
This is how a hypothesis is typically stated in scientific research.
Even if we were to go along with the Soden Study that oral DMSA could not pull any significant amount of heavy metals from the bodies of autistic children, we have to consider the possibility that the sulphur-based drugs – DMSA and DMPS – were doing something to make the children feel better.
The Soden Study did acknowledge this possibility in their discussion. Many families have reported their autistic children responded favorably when treated with chelators like DMSA or DMPS
John Yeo, MSc. RAc.
9 September 2007.