You may be aware that November 1-6 is ‘Vaccine Awareness Week’ (a reminder from Darcy, over at SciBlogs, prompted my previous post.). Those who originally gave the week this label are actually strongly-antivaccines, so all the more reason for some science-based discussion around it as well :)
In one of our first-year labs we get students to compare the rates at which pancreatic lipase (a fat-digesting enzyme produced in the pancreas) breaks down fat in the presence and absence of calcium ions, Ca^2+. Calcium is a co-factor, needed to optimise the enzyme’s action. It’s normally present in pancreatic secretions, which are what we start from in the lab, so in order to look at the lipase’s action in the absence of Ca^2+, we have to remove the ions using dialysis and a chelating agent, EDTA.
Chelating agents are an important tool for doctors treating patients suffering from heavy-metal poisoning, as they bind to the metal ions and these chelator+ion complexes can then be removed, typically by excretion through the kidneys. This isn’t as straightforward as it might sound: some types of chelator bind may not bind strongly to their targets but are readily excreted, while others bind quite well but may just shift the metal ions from one part of the body to another. So using chelators is a skilled process used by people who really, really know what they’re doing.
Nonetheless, in the US – and elsewhere – many of those who are anti- vaccination because they a) wrongly believe childhood vaccines to cause autism and b) believe that this is due to mercury (Hg) in the vaccines, have seized on chelation as a ‘cure’. It would be nice to say that NZ was excluded from ‘elsewhere’ but I’m afraid this isn’t so. A quick search finds nzhealthnet providing in full US-based material that makes all sorts of claims about the supposed links between autism and exposure to mercury (ably debunked elsewhere, by Orac and Ben Goldacre among others), and actively promotes chelation as a ‘therapy’ for autistic children.
Discussing the use of chelation, in the context of a proposed ‘trial’ with autistic children was later withdrawn, Orac has commented that the
hypothesis is that autism is in fact a form of mercury poisoning is the basic hypothesis being tested here, with the corollary being that chelation can remove that excess mercury and alleviate the symptoms of autism. Neither the main hypothesis, nor its corollary is supported by compelling evidence. Indeed, it doesn’t even have biological plausibility going for it, as it in essence postulates that some sort of mercury exposure (from those evil vaccines, naturally) caused some sort of brain damage in infants that led to autism months to years later. Even if mercury in vaccines did cause damage leading to autism, that such damage could be reversed months or even several years later by chelation defies scientific plausibility based just on biology alone.
And he goes on to say:
But it’s more than just scientific plausibility. In any normal trial, especially on children, there has to be good preclinical evidence supporting the hypothesis. There should, for instance, be animal models showing that mercury exposure does indeed cause autistic symptoms and that chelation therapy alleviates those symptoms. There should be cell culture and animal models showing a plausible physiological mechanism. (Throwing a bunch of thimerosal on neurons in cell culture then noting that some of them die doesn’t count. I could do that with bleach, but that wouldn’t prove that bleach causes autism.) Absent strong animal data, there should be high quality observational data in humans that support the hypothesis; for example, compelling, strong, and consistent evidence that autistic children do have higher mercury exposures and higher mercury levels indicative of chronic mercury poisoning. There are no such data, and the usual data presented as “evidence” that mercury poisoning causes autism is of such poor quality that they don’t deserve to be called “data.” Most of all, however, the drug to be used, DMSA, is not risk-free.
Now, this rang alarm bells, because back on nzhealthnet their expert is claiming that DMSA is perfectly OK to use. In fact, an examination of DMSA used for lead toxicity in rats found it worked just fine in animals given a toxic dose of lead. But – a big but – a control group, not exposed to lead but treated with DMSA, suffered ‘lasting cognitive impairment’, & the study’s authors went on to conclude that treatment [with this chelating agent] should be strongly discouraged for children who do not have elevated tissue levels of Pb or other heavy metals. In the States EDTA has also been promoted as a chelator for purposes of removing mercury from children’s bodies. Unfortunately, as students learn in our first-year labs, EDTA is a strong chelator of calcium. Used wrongly (eg at high levels over short periods of time) it can cause blood & tissue Ca^2+ levels to drop very rapldly indeed. Calcium’s involved in muscle contractions (among other things), so a deficit of calcium can really mess up muscle action – including of that very important muscular organ, the heart…
So… there is no good evidence of a causal link between mercury in vaccines and development of autism. (And besides, childhood vaccines have been mercury-free since 2001 – with no decline in reported rates of autism.)
There is no good reason to expose children to chelation for supposed mercury ‘toxicity’, and good ethical reasons not to.
And – given that so many in the anti-vaccine movement seem to espouse ‘all-natural’ & eschew ‘artificial’ – I find it gobsmackingly hypocritical that they can also promote use of chemical ‘cures’ … (Not least, in the US again, the use of an industrial chelating agent as a ‘food supplement’…sold, I am saddened to see, by folk who also promote the dreadful MMS.)