Friday, 15 November 2013

Iodine deficiency and autism

With all the recent-ish chatter about dietary quality for those on the spectrum (see here), coupled with a hint of something like the mechanisms of malabsorption being linked to specific cases (see here), the potential issue of 'nutritional deficiency' in relation to autism represents a pretty constant research topic these days.
 Iodine @ Wikipedia

I've talked before about research defining a deficiency in certain vitamins and minerals in relation to cases of autism on this blog; be it in relation to the vitamin-of-the-hour, vitamin D (see here) or vitamin B12 (see here) or something like zinc (see here).

The picture is a complicated one and not necessarily a universal one in terms of prevalence across the autism spectrum nor being solely due to poor eating patterns. But given the increasing understanding of the importance of nutrition to mental and physical health and wellbeing, one would expect quite a lot more to be said on this topic over the coming years.

The paper by Rasha Hamza and colleagues* detailing findings in relation to iodine in cases of autism and other family members adds to the interest. Based on a relatively small participant group, the authors reported that: "Of autistic children and their mothers, 54% and 58%, respectively, were iodine deficient". This contrasted with none of the 50 control group children or mothers presenting with iodine deficiency (ID).

Before progressing through the Hamza study further, I might point out that the British Dietetic Association (BDA) carries quite a detailed information sheet about iodine (see here) as does the US Office of Dietary Supplements (see here). Iodine is sourced mainly from food, and as you'll see from the links, outside of seafood and shellfish, milk and dairy products are one of the biggest dietary sources of iodine. Casein-free diet anyone?

A primary use for iodine in the body is for the production of thyroid hormones. Without going over previous ground, there is some research history when it comes to thyroid hormone and autism as per discussions on the measurement of thyroid hormone levels in autism (see here) and more recent research talking about maternal thyroid levels and offspring 'autistic symptoms' (see here). Dare I even mention the possible environmental variables which have been associated with thyroid function too?

Back to the Hamza paper. As well as measuring levels of urinary iodine (UI) - which apparently is quite a good way of measuring iodine intake** - the researchers also scored child participants with autism using the CARS so as to have some measure of the extent of their presented symptoms. That and examining levels of some of the various thyroid hormones, they were able to arrive at a few other preliminary, but potentially important conclusions.

"Childhood Autism Rating Scale (CARS) score correlated negatively with UI (r = -0.94, p <0.001)". I'm no statistician (add it to the long list of things for which I'm more amateur than professional) but a correlation (r) of -0.94 seems pretty good to me bearing in mind that (1) or (-1) indicates a perfect positive and negative correlation respectively. This data translates as a higher CARS score being generally associated with lower levels of urinary iodine. Further, when looking maternal and child UI output and other thyroid hormones, the authors reported some interesting positive correlations between child and mother values obtained.

It would be easy to say that the Hamza study has some methodological issues. Outside of the quite small participant group, and their exclusive focus on Egyptian families, this was very much a snapshot study in terms of looking at participants at a particular point in time. CARS, like many other autism screening and assessment instruments, is still quite a subjective measure also and who's to say that if this study was repeated a week or a month later, whether similar results would be had with the same group. And then there is that milk-free dietary issue to also consider...

But with all that in mind, this remains an interesting study. I note that other independent groups have also reported issues with iodine being related to cases of autism as per the findings by Blaurock-Busch and colleagues*** (open-access here) and a familiar name to this blog (see here) Jim Adams and his paper***. I was also drawn to an interesting communication on the topic of iodine deficiency as being related to autism from Sullivan & Maberly**** as food for thought, bearing in mind I'm less inclined to believe there is just one factor linked to the increasing numbers of cases of autism being reported.

So, perhaps on that collected basis, there is a little more research to do when it comes to iodine and autism? Oh, and with my blogging caveat about no medical or clinical advice given or intended, please take some proper medical advice if you're thinking about supplementing with iodine (see here).

To close, The Life of Riley by the Lightning Seeds (not to be confused with the life of Whiteley).

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* Hamza RT. et al. Iodine Deficiency in Egyptian Autistic Children and Their Mothers: Relation to Disease Severity. Arch Med Res. 2013 Oct 9. pii: S0188-4409(13)00222-1. doi: 10.1016/j.arcmed.2013.09.012.

** Delange F. et al. Determining median urinary iodine concentration that indicates adequate iodine intake at population level. Bulletin of the World Health Organization. 2002; 80: 633-636.

*** Blaurock-Busch E. et al. Toxic Metals and Essential Elements in Hair and Severity of Symptoms among Children with Autism. Maedica (Buchar). 2012 Jan;7(1):38-48.

**** Adams JB. et al. Analyses of toxic metals and essential minerals in the hair of Arizona children with autism and associated conditions, and their mothers. Biol Trace Elem Res. 2006 Jun;110(3):193-209.

***** Sullivan KM. & Maberly GF. Iodine deficiency as a cause of autism? BMJ. Rapid Response. 13 October 2004.

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ResearchBlogging.org Hamza RT, Hewedi DH, & Sallam MT (2013). Iodine Deficiency in Egyptian Autistic Children and Their Mothers: Relation to Disease Severity. Archives of medical research PMID: 24120386