Sunday, 20 February 2011

'Leaky gut' and autism

OK, I'm on a bit of a roll; what with this being my first blog. The next topic that I want to discuss is one quite close to my own research, namely 'leaky gut' and autism. Leaky gut is a little bit of a misnomer. In reality from what I believe, we all have a leaky gut to some degree; the issue at hand is that permeability of the gut is perhaps increased (hyperpermeability) at least in some cases of autism.

I will admit that it has always been fascinating to think that what goes on in the gut could influence behaviour and possibly facets of development and that hyperpermeability might contribute to this. Coeliac disease - that exquisite sensitivity to gluten (celiac to the non-UK audience) has long been associated with gut permeability issues. Looking at the co-morbidity of coeliac disease and autism, it is clear that whilst there is probably no universal relationship, it does occur and perhaps at levels greater than expected in non-autism populations.

The study by Genuis reported a case where autism and coeliac disease was diagnosed and a gluten-free diet introduced. The diet positively affected presented gastrointestinal symptoms but also seemed to affect the presentation of autistic symptoms.  The trouble is that coeliac disease is not routinely checked for in autism (it involves taking a blood sample and possibly a biopsy, so there are ethical considerations).

Anyway back to hyperpermeability, for many years the only study suggestive of hyperpermeability of the gut in autism was that by D'Eufemia and colleagues. They found hyperpermeability in just over 40% of the people with autism involved in their study. That was back in 1996. It was a long time before anything else was done specifically with this issue in mind although there was the odd attempt. Fast forward to 2010 and Laura de Magistris and colleagues published their study suggesting that enhanced gastrointestinal permeability was present in just below 40% of their group. The added value to the de Magistris study was that they had a good size experimental group (90 children) who were well defined in terms of autism diagnosis (ADOS, CARS), a good size control group (64 children), they looked at first-degree relatives and they also looked at what happens to gastrointestinal permeability following use of a gluten- and casein-free (GFCF) diet. Their results were interesting: being on a GFCF diet seemed to reduce the level of permeability present. They even went as far as to suggest that intestinal permeability may be a marker for identifying the sub-group of people with autism who might benefit from such dietary intervention. Don't get me wrong, there is an awful lot of questions that still need to be answered on this whole approach. We have tried to deal with some of them in one of our peer-reviewed papers (read it here) including the negative results from Robertson and colleagues. Still, if there is a subset of people with autism who also may present with coeliac disease or hyperpermeability of the gut, science should be doing more to try and find them. After all, from all the data so far, we know that autism does not confer protection against other conditions, diseases or co-morbidities.