More and more autism researchers are concluding that autism may result from a combination of genetic susceptibility and exposure to environmental toxins, such as heavy metals, at critical periods during brain development. As we saw in part 1, there is growing evidence that detoxification systems are impaired in autistic children and their ability to excrete toxins is decreased. This can lead to unacceptably high levels of toxic heavy metals like lead and mercury in the body and brain.

Treatment for heavy metal toxicity involves removing the metals from the body with chelation therapy. Chelation therapy for autism is practiced worldwide despite mainstream medicine’s assertion that there is no credible scientific evidence to support it. One specific type of treatment, DMSA chelation therapy, is the most commonly used chelation therapy for children with autism because it is considered gentler and safer than other chelation therapies and has been researched for this condition. 

What is chelation?

Chelation has its origin in the Greek word chele, meaning claw of a lobster, and thus depicting the concept of clinging or holding with a strong grip.[1] Chelating agents are compounds capable of binding metals to form complex ring-like structures. After metals are bound, the metal-chelating complex is excreted through the kidneys and urine. Chelation enhances the elimination of metals (both toxic and essential) from the body and is used in medicine to ameliorate metal toxicity.

The use of chelating agents is accepted in mainstream medicine for the treatment of acute metal poisonings but is not well-accepted or widely used for lower-dose, more chronic exposures. Nevertheless, both conventional physicians, such as those that specialize in environmental medicine, and integrative/natural physicians around the globe use chelating agents for the treatment of chronic heavy metal toxicity, including children with autism.[2]

What is DMSA chelation?

DMSA, also called succimer, is one of the chelating agents currently used in the United States. It is an oral medication that is FDA-approved to treat mild-to-moderate acute or chronic lead toxicity in children and adults, as well as acute mercury intoxication.[2] It is considered an efficient, but not strong, chelating agent that has a good ability to bind to lead and a lesser ability to bind to mercury.[2] Since DMSA does not effectively bind the essential elements calcium, copper and zinc, DMSA is considered suitable for children and sensitive adults and has a history of safe use in children for chelating lead and mercury.[2]

Research on DMSA chelation therapy for autism

A handful of studies so far have examined whether oral DMSA chelation improves behavior in children within the autism spectrum. The first major study, published in 2009 in BMC Pharmacology and Toxicology, found some improvement in autism symptoms.[3,4] This study involved two phases. Phase 1 involved 65 children, aged 3 to 8, with autism spectrum disorders. They received one round of DMSA therapy (10 mg/kg per dose, in 3 doses per day) for three days. During phase 1, urine metal levels were measured at baseline, after one dose of DMSA, and after the third day of DMSA treatment (after one round).

There were very large and extremely statistically significant increases in excretion of lead after the first dose and after round one, indicating high body burdens of lead.[3] There was also a large and highly significant increase in excretion of mercury after the first dose.

Children with high excretion of toxic metals (arbitrarily defined as above the laboratory’s reference range, defined as the top 95% for typical children who are not undergoing chelation therapy) were allowed to continue on to phase 2. In phase two 49 participants were randomly assigned to receive six additional three-day rounds of either DMSA or placebo with 11 days in-between, for a grand total of seven rounds.

Urine metal levels were measured after the second 3-day round of DMSA and again at the end of the last round.[3] For five participants, urinary excretion of toxic metals had decreased below the cut-off after completing two rounds of DMSA therapy in phase two and therefore they did not continue with the rest of Phase 2. For the rest of the participants, the increased excretion of lead persisted throughout the entire study, and mercury excretion also generally continued with some fluctuations.

77% of children showed improvements in autism symptoms

Autism severity was assessed by certified evaluators and parents before phase 1 and before and after phase 2 using five different standardized assessment tools.[4] Surprisingly, results from three of the five assessment scales showed that one round of DMSA chelation therapy had nearly the same benefit as seven rounds. The other two assessment tools found somewhat more improvement in the 7-round group, but the difference was not statistically significant. Overall, about 77% of the participants had improved autism severity scores, about 12% had no change, and about 11% had a worsening of their scores.[4]

So, although the DMSA treatment appeared to be beneficial in most cases, there was a small subset whose symptoms appeared to worsen slightly. The most common adverse effect seemed to be hyperactivity and this effect was usually temporary, according to the researchers.

DMSA safety was also evaluated

The children had regular blood tests throughout the study to make sure liver and kidney function and blood cells remained normal. The treatment did not cause any significant changes in these lab results.[3] To prevent depletion of essential minerals, the children took a multivitamin/mineral starting two months before therapy and continued it during therapy. DMSA did significantly increase urinary loss of potassium and chromium on the days it was taken, so the researchers recommended supplementation of chromium and potassium and/or increased intake of fruits and vegetables.[3]

More treatment may be needed to reduce heavy metal levels

It seems likely, according to the researchers, that longer treatment duration may have yielded even more beneficial results, since 80% of the children were still excreting high levels of lead and other toxic metals at the end of seven rounds of DMSA chelation therapy.[4]

“It appears that monitoring urinary excretion of toxic metals may be a useful guide as to how long to continue therapy,” said the study authors.[4]

The latest study to be published examining whether DMSA benefits children with autism looked at 44 Saudi Arabian children with autistic spectrum disorder between the ages of three and nine.[5] In this study, which unfortunately had no control group, heavy metal levels were measured in urine and then a DMSA challenge test was performed to compare heavy metal levels before and after a standard dose of DMSA.

Urine tests performed after the DMSA challenge test reflected the accumulated or relative body burden of metals, according to the researchers, rather than levels from recent exposure which are only reflected in the baseline test results.

As expected, the DMSA challenge test increased the urine metal output for a number of potentially toxic metals, especially lead, mercury, and cadmium, all of which increased from baseline by a statistically significant amount, which the investigators interpreted as indicating a high burden of these metals stored in the children’s tissues.

Six months of DMSA chelation decreases autism symptoms

The children were then treated with DMSA chelation therapy for six months, with each child taking one single dose of DMSA (10 mg/kg body weight) per month. After the six month treatment period, results showed that typical autism behavioral symptoms were reduced with DMSA chelation therapy. A comparison between standardized questionnaires and assessment scores before and after the chelation program showed improvements for:

• Verbal and nonverbal communication
• Taste, smell, and touch
• Relating to people
• Adaptation to change

The researchers concluded that DMSA chelation therapy for autism increases the excretion of toxic metals and has a beneficial effect on autism symptoms. Unfortunately, another DMSA challenge test was not reported to have been performed after the six-month treatment. This would have indicated whether the children were still excreting high amounts of heavy metals in their urine and would have provided information as to whether the therapy was reducing the overall body burden of metals and if so, by how much.

Overall evidence for DMSA chelation therapy for autism inconclusive but promising

Recently, a large team of researchers lead by Tonya Davis, PhD, Assistant Professor of Education Psychology at Baylor University in Texas, conducted a systematic literature review of studies that have evaluated the effects of chelation on autism.[4] They found and analyzed a total of five studies, four of which reportedly found mixed results and one of which reported positive results. There were significant problems with the methodology of all the studies, according to the researchers, and therefore they concluded that the research does not support the use of chelation as a treatment for autism.

Another recent review of studies, just published in 2014, investigated all kinds of research to-date on the potential associations between environmental toxins and autism.[7] Their review included 40 studies reporting measurements of heavy metals in children with autism compared with control children and concluded that the cause of autism may involve, at least in a subset of children, complex interactions between certain environmental toxins and genes.

Their review also included 12 studies that reported improvements in levels of toxins or in autism symptoms in children using detoxification therapies, including DMSA chelation therapy.[7] Although no significant adverse effects were reported in these studies, the fact that none of these studies contained a control group or were placebo controlled led the investigators to conclude that, “additional studies examining detoxification methods in children with autism spectrum disorder are warranted to confirm the effects of these treatments.”[7]

How to make a decision about DMSA chelation therapy for autism

Ideally, future studies will use better methodology. Results from larger and higher quality trials will help further clarify whether chelation therapy for autism is truly a safe and valuable treatment for diminishing symptoms. Until then, despite the strong opposition from medical toxicologists, some environmental physicians, integrative MDs, naturopathic physicians, and parents of autistic children will choose to use DMSA chelation therapy based on the available preliminary evidence that chelation may be helpful and safe. Keep in mind that chelation therapy for autism is almost never used as a stand-alone treatment. Besides heavy metal exposure, other toxic chemical exposure, nutritional inadequacies, metabolic problems, food and chemical sensitivities, and digestive dysfunctions may all be involved in autism and may all need to be addressed for the best possible outcomes.

To learn more, you can find a DMSA chelation therapist in the NHA Physician and Practitioner Directory.

Share you experience

Have you tried DMSA chelation therapy for your child’s autism? Was it effective? What other strategies have you tried?
Originally published in 2014, this post has been updated.

[1] Int J Environ Res Public Health. 2010;7(7):2745–2788.

[2] BJMMR. 2014;4(9):1821-1835.

[3] BMC Clin Pharmacol. 2009; 9: 16.

[4] BMC Clin Pharmacol. 2009; 9: 17.

[5] Maedica (Buchar). 2012 Sep;7(3):214-21.

[6] Res ASD. 2013;7(1):49-55.

[7] Translational Psychiat. 2014;4:e360.