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Are blood mercury levels an important metric in autism?

Posted Oct 25 2009 11:01pm

A recent study shows that autistic children do not have more mercury in their blood than typical children. When it came out I didn’t have time to discuss it. I have some time now, and other people have blogged it, so I decided it was time to address some thoughts here.

The study, from the U.C. Davis MIND Institute: Blood Mercury Concentrations in CHARGE Study Children with and without Autism concluded:

After accounting for dietary and other differences in Hg exposures, total Hg in blood was neither elevated nor reduced in CHARGE Study preschoolers with AU/ASD as compared with unaffected controls, and resembled those of nationally representative samples.

This paper and its conclusion were sure to be criticized by the alternative-medical autism community. Why? because the autism communities are still battling the idea that autism is a “novel” form of mercury poisoning. Anything, no matter how small, that challenges that idea will be (and is) challenged.

The idea that autism and mercury poisoning are similar was put forth in a paper in the pseudo journal Medical Hypotheses. The paper, Autism: a novel form of mercury poisoning, by SafeMinds founders Bernard S, Enayati A, Redwood L, Roger H, Binstock T., purported to show similarities in autism and mercury poisoning.

The abstract of the SafeMinds paper states:

Autism is a syndrome characterized by impairments in social relatedness and communication, repetitive behaviors, abnormal movements, and sensory dysfunction. Recent epidemiological studies suggest that autism may affect 1 in 150 US children. Exposure to mercury can cause immune, sensory, neurological, motor, and behavioral dysfunctions similar to traits defining or associated with autism, and the similarities extend to neuroanatomy, neurotransmitters, and biochemistry. Thimerosal, a preservative added to many vaccines, has become a major source of mercury in children who, within their first two years, may have received a quantity of mercury that exceeds safety guidelines. A review of medical literature and US government data suggests that: (i) many cases of idiopathic autism are induced by early mercury exposure from thimerosal; (ii) this type of autism represents an unrecognized mercurial syndrome; and (iii) genetic and non-genetic factors establish a predisposition whereby thimerosal’s adverse effects occur only in some children.

The paper is discussed on the SafeMinds website as a “cornerstone document”:

In April of 2000, SafeMinds founders put forth the first definitive work reviewing the link between mercury and Autism Spectrum Disorders. This effort showed that the autism presentation mirrored mercury toxicity. This research was key to propelling the issue into the awareness of the public and government officials. The resulting report, “Autism: A Novel Form of Mercury Poisoning” (Bernard, Enayati, Redwood, Roger, Binstock) was and remains recognized as a cornerstone document to the discourse on medical mercury exposure and toxicity and its effects on health.

They still hold to this idea, even though the it has been thoroughly rejected by actual specialists in mercury toxicity. Heck, it’s been rejected by non-specialists. Autism and mercury poisoning are just not the same thing.

If you spend any time with the online autism community you already know the mercury hypothesis is still alive and well. Chelation, a drug therapy to remove some of the body’s mercury burden, is still applied to autistics by alternative medical practitioners. Join one of many autism discussion groups and the idea is bound to come up.

Given that, it may seem counterintuitive that the evidence for the mercury hypothesis is so weak that any study that purports to support it is quickly cheered by the alternative medical community.

Such was the case when, in 2007, two researchers looked at what was then an already existing dataset of blood mercury levels in autistic children and declared that contrary to the previous reports, autistic kids do have high levels of blood mercury. The reanalysis paper, Blood Levels of Mercury Are Related to Diagnosis of Autism: A Reanalysis of an Important Data Set, was itself immediately reanalyzed ( epiwonk, epiwonk-2, Autism Street, leading to a response analysis by the Age of Autism blog, to name a few).

The quick and multiple responses to the DeSoto paper serve show how important the idea of autism as mercury poisoning is in some circles.

Shortly after the DeSoto paper came out, Mark Blaxill of SafeMinds (a very vocal proponent of the mercury hypothesis) wrote at the Age of Autism blog:

This is an important and unexpected finding. It supports one of the central hypotheses at the heart of the autism-mercury controversy and suggests that the excretion deficit in autistic children might persist longer than anyone had guessed

Mr. Blaxill has also used the DeSoto paper in his congressional briefing to support the idea that “Autistic children metabolize mercury differently”. Beyond the question of whether DeSoto is an accurate analysis of the data, this assertion by Mr. Blaxill is clearly not what the DeSoto paper showed.

That said, Mr. Blaxill’s remarks show how the DeSoto paper was obviously a major milestone in the attempt to legitimize the mercury hypothesis.

This struck me as odd at the time, as the prevailing wisdom was (and remained) that blood levels of mercury were not a good metric. Check any autism-biomed discussion and you will find loads of discussions about all sorts of odd tests for mercury: chelation challenge tests, urinary porphyrin tests, hair tests…pretty much everything except blood tests. The reason is simple, and sad. Autistic kids aren’t suffering from mercury poisoning, and blood tests show it.

The recent MIND Institute paper clearly refutes the DeSoto analysis paper. The MIND study is larger and uses a cohort of kids of similar ages (DeSoto uses a broad age range) and, very importantly, the MIND study controls for mercury exposure from diet and other sources. These are factors missing in the data analyzed by DeSoto. This puts the alternative medical autism community into a bit of a quandary. The MIND Institute and the lead author (Dr. Hertz-Picciotto) are well respected in those quarters as they generally support the idea of a real rise in autism incidence and the idea that vaccine-causation should be researched. And, yet, the MIND study would speak against autism as mercury poisoning.

One thing about waiting to do a longer blog post is that I can see what others have said. For example, the comments over at the Age of Autism blog were predictable in suggesting that blood levels are not an accurate metric. Here are a cpouple of examples:

This study on children’s BLOOD mercury levels does not take into account the fact that the mercury (and aluminum) is stored in tissues and organs including especially the BRAIN. The body protects itself from heavy metals by encapsulating this in fat cells especially, and in an infant or child, the largest concentration of fat is in the brain. The vast majority of the mercury (and/or aluminum) is NOT IN THE BLOOD.

and

Blood levels are always inaccurate. Best to get urine after chelation, then you see the difference. Even kids with autism, after many rounds still don’t dump the stuff. And by the way, selenium soils is a key thing Maria…because the lowest selenium soil states have the highest autism. And visa versa. Lest we forget, many other metals also cause problems…did they look at those or bother?

And let’s get this straight…mercury not only causes autism, it causes behavioral problems, immune problems, metabolic problems….just looking at one aspect of the outcome is not a study.

Another desperate attempt to downplay mercury, not going to work guys…

I bring this up because similar observations were not made when the DeSoto paper was being discussed. Yes, even though the prevailing wisdom is that blood levels of mercury are not the “correct” metric, none of the people at blogs like the Age of Autism spoke up.

Back to the present, I note also the SafeMinds response to the MIND Institute study, which includes this line:

Research has demonstrated that certain subgroups, including children with autism, show potentially higher susceptibility to environmental stressors like mercury (James, 2009; Ralston, 2008; Sajdel-Sulkowska, 2009). Some recent studies have indicated increased mercury in tissues and organs of people with autism relative to controls (Adams, 2007; Sajdel-Sulkowska, 2009; Desoto, 2007; Desoto, 2008). Given equivalent exposures, as indicated by the CHARGE study, SafeMinds feels that it is imperative that research is conducted that determines not only exposure, but differences in how individuals with autism handle mercury exposures and its impact to the body’s tissues and organ systems.

Yes, that is the same DeSoto paper they are citing. I am a bit of a loss as to what SafeMinds is trying to say. They cite DeSoto, an analysis of a study which did not control for exposure and because of this is a paper which to this observer is clearly refuted by the MIND Institute study. Without controling for exposure, DeSoto can’t be claimed to show increased mercury in tissues.

Sound confusing? That’s because it is. Mercury in the blood is important to the biomed community. At least it is if it is a paper (like DeSoto) that supports the idea that mercury causes autism. Mercury in the blood is not important if the paper (like the one from the MIND Institute) doesn’t support the link. The DeSoto paper is important because it supports the hypothesis, even when SafeMinds are using the MIND study which refutes DeSoto…

Yes, all this is confusing. There isn’t a consistent view on whether blood levels are important, except to say that data which supports the mercury hypothesis is good, data which doesn’t is bad.

If this is so confusing, what can we say? We can say that no, mercury in the blood is not a good metric for anything having to do with autism. Not because blood levels aren’t a good measure, but because autism is not a novel form of mercury poisoning.

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