Saturday, 17 September 2011

Carbs and dysbiosis in autism

Yes, its another quick post on gastrointestinal factors potentially being related to some cases of autism spectrum conditions. Indeed the paper at the centre of this post is, dare I say, perhaps one of the most important papers that I have covered thus far in terms of the research group involved and most importantly their findings. Strong words I think you would agree, so read on and judge for yourself.

Brent Williams and colleagues* have published a paper today in PLoS ONE on the subject of carbohydrate digestion and intestinal dysbiosis in children with autism. The paper is full-text and can be accessed here.

There is little point in me going through the paper in great detail 'cos it is open-access. I will therefore summarise what I see as the important bits.

  • Tim Buie is on the authorship list. You might remember him from various gastrointestinal (GI) related snippets in cases of autism spectrum conditions. The 'Autism Now' series on PBS NewsHour not so long ago. Lactose intolerance potentially being pretty widespread in some cases of autism. The AAP guidance on managing GI factors in autism. Not a bad list of achievements if I do say so myself.
  • A pretty well defined group of children with autism also presenting with GI problems (n=15) pitted against a control GI group (n=7). Participant numbers were fairly small so get ready with that pinch of salt.
  • The children with autism and GI problems studied may have altered genes involved in digestion according to the press release.
  • Microbial dysbiosis is present and potentially tied into the genes controlling the enzymes used to break down carbohydrates (dissacharidases).
  • Lots of different associations between various species of GI bacteria in the autism group. Bacteroidetes, Firmicutes and even some 'unclassified' bacteria present. Our old friends Clostridia were also noted with some important messages in relation to the timing of onset of GI symptoms. Importantly, they looked at 'ratios' between phyla/species and also looked in different parts of the gut. 
  • Author hypothesis: dissacharidase and hexose transporter problems alter the gut environment with regards to carb metabolism and provide a rich hungry hippo supply of material for bacteria to feast on and do their worst. A possible reason for the effectiveness of the gluten- and casein-free diet in some cases of autism? How about the specific carbohydrate diet (SCD)?

I am a bit tired right now (local time is past midnight) so perhaps will provide a more extensive overview of this paper outside of the Nosferatu period. Happy reading and good night.

* Williams B. et al. Impaired carbohydrate digestion and transport and mucosal dysbiosis in the intestines of children with autism and gastrointestinal disturbances. PLoS ONE. September 2011.