Monday, 7 November 2011

The link with zinc

A while back on this blog, the mineral zinc was discussed in relation to quite a few things ranging from the common cold to alcohol metabolism to developmental conditions like autism and ADHD. The collected data on zinc and ADHD were perhaps most interesting and most suggestive of some relationship between reduced levels and specific symptoms like inattention, with the fairly large caveat of a need for more detailed study.

A possible link between zinc and autism was a little more tenuous; some limited suggestion of zinc deficiency in some cases but at the same time reports of an excess of zinc also being found in other cases. A new paper enters the zinc arena followed by some pretty big headlines.

The paper by Hiroshi Yasuda and colleagues* (full-text) reports on measures of hair zinc concentrations from quite a large group (n=1967) of children with autism. Based on ICP-Mass Spectrometric analysis, the authors report that a sizeable proportion of their participant group (males 0-3 years old: 43.5%, females: 52,5%) seemed to be deficient in zinc compared with other reference ranges. They go on to suggest that perhaps through epigenetic processes such deficiency might be contributory to the aetiology of autism (in some cases).

As per such findings, media headlines follow, such as this one from the UK Daily Mail 'Children with low levels of zinc may be at higher risk of autism'. Fairs fair, the headline is balanced by a couple of comments on the lack of appropriate control groups and whether results imply causation or are merely epiphenomenal.

I am however intrigued by this data. Whilst not disagreeing with the requirement for appropriate independent age- and sex-matched control groups when looking at any sort of parameter for autism or anything else, I note that the reference ranges used were actually partially derived from the same research team under different publication coupled with other datasets. I suppose this point would be remedied further by more control population data being produced by the same lab; so looking at comparison groups like learning disability or speech and language disorder (without autism) for example. The accompanying point about ensuring that ethnicity was also controlled for might also be relevant.

Irrespective of any autism-causation link or not, here are results which suggest that quite a large number of children might be pretty deficient in what is quite an important mineral. The question must surely be asked, why? I note that the words 'leaky gut' crop up in the paper as one possible explanation and no doubt some people will have read this and sighed, 'not that again'. As mentioned quite a few times on this blog, hyperpermeability of the gastrointestinal membrane is however slowly starting to move out of the realms of fantasy as being documented in at least a proportion of cases of autism spectrum conditions. Remember de Magistris and colleagues? As per what happens in other conditions where leaky gut is present, deficiencies of nutrients occurs and only when permeability issues are put right do you see something approaching normal absorption. There is also some indication that, in certain bowel complaints, zinc might also play a role on the gut barrier function. It makes me wonder whether any of this participant group were screened for malabsorption causing states like coeliac disease or perhaps even just given the mannitol lactulose test?

I look forward to seeing more research done on zinc and other vitamins and minerals with regards to autism and related conditions. Knowing what problems in early nutrition might be capable of from things like the Barker hypothesis, the onus is surely to investigate such issues further. I must finally add that I am in no way advocating supplementation with zinc or any other nutrient without the appropriate clinical supervision. Don't mess with the vitamins and minerals man!

To finish a touch of spoof metal from the Darkness.

* Yasuda H. et al. Infantile zinc deficiency: association with autism spectrum disorders. Scientific Reports. November 2011.