Greetings Earthlings! 🙂

Today I’m going to discuss the issue of digestive problems for people on the spectrum- but don’t worry, I’ll stick to the science! I won’t regale you with any personal tales on this occasion 😛 😉

Gastrointestinal (GI) problems are among the most commonly associated conditions with autism.

Evidence suggests that autists may be over 3.5 times more likely to suffer from issues such as diarrhea, constipation, food allergies, gastroesophageal reflux disease (GERD), irritable bowel syndrome (IBS) and inflammatory bowel diseases (i.e. Crohn’s disease and ulcerative colitis).

I know- not the most pleasant of subjects, but we can all be adults right? 😉

Joking aside- these are serious issues for people with autism, especially for children. Autists are already sensitive to such stimuli as sound and touch. Adding GI discomfort to the mix can make things so much more difficult. The associated pain from these conditions can worsen behaviors, and in some cases, trigger regressions.

So what does science have to say about all of this?

As with autism, it’s another game of Cluedo- research is ongoing to determine ‘who-dunnit’. There are many suspects, but the culprit remains unclear.

Bacterial Abnormalities & Carbohydrate Digestion-The gut is home to trillions of bacteria naturally living in harmony with us.  Our gut provides them with food and shelter, and in return they digest certain dietary substances and produce vitamins B and K for us to absorb. This forms what is known as the gut microbiome. Ordinarily bacteria and host exist in harmony, however, if there is an overabundance of certain bacterial strains, this can lead to a number of GI problems. Studies have shown that such overabundance exists in children with autism.

Abnormalities in carbohydrate digestion have also been reported in cases of autism. The cells of the intestines appear to have difficulty in breaking down and transporting carbohydrates in the gut causing malabsorption of these vital nutrients.

It’s been suggested that these issues with carbohydrates may be connected to the high level of bacteria present in the autistic gut as digestive alterations may influence nutrient availability within the microbiome, but further investigation is needed.

Furthermore, in recent years, evidence is emerging that gut microbes can influence brain development and behavior!

Wuttttttt???!!!

I know!!!

In particular, there is evidence to suggest that people with autism are missing one specific bacterium- Lactobacillus reuteri.

One study in mice showed that following the addition of this bacterial strain to their diet,  the natural microbiome of the was gut restored AND further restored some behaviors associated with ASD’s! Interestingly, L. reuteri promotes the production of oxytocin, which as previously discussed, is essential for human bonding and social behavior.

Who knew that bacteria could control our brains this way?!

Brain-Gut Communication and the Role of Serotonin-As in the picture below, the brain and the gut share a very close relationship in the human body.

The gut in actual fact has it’s own complex nervous system (the enteric nervous system) which regulates the activity of the gut- kind of like a second brain. Together, the gut and the brain form what is known as the brain-gut axis, a two way street where each can influence the other. For example, signals travelling from gut to brain can influence satiety, whereas stress/anxiety signals from the brain to the gut affect gut sensitivity.

Serotonin is an important neurotransmitter (chemical messengers that allow neurons to communicate) within this axis. For example, serotonin plays an important role in the control of intestinal motility. As such, alterations in serotonin levels have been implicated in a number of GI problems.

But how does this relate to autism?

Yep- you guessed it, serotonin levels, like oxytocin, are dysregulated in autism, and therefore likely contribute to associated GI issues.

Further to this, there is also evidence to suggest that certain gut bacteria are involved in the production of serotonin in the body by interacting with serotonin producing cells (enterochromaffin cells). So perhaps alterations in these serotonin producing bacterial colonies may also contribute to these GI issues.

Diet-As people with autism often have restrictive eating habits, it was proposed that perhaps diet may contribute to GI issues. However, studies have shown that although autistic diets may differ, overall nutritional intake does not. On the other hand, many people report improvements in both GI and autistic symptoms following gluten (a protein found in grains like wheat) and casein (a protein found in dairy) free diets, but there is insufficient scientific evidence to support this.

Genetics- Finally, scientists believe that as with autism, genetic abnormalities likely contribute to these GI issues. Moreover, as autism and GI problems are so frequently linked, researchers have suggested that perhaps they both share the same underlying genetic mutation or may be caused by some other unknown biological mechanism.

So there we have it! 🙂

Hope you enjoyed this ‘alimentary’ introduction to digestive issues and the spectrum! 😉

Aoife