Autism and bacteria

Greetings Earthlings! 🙂

Leading on from my previous post about digestive issues and autism, this week I’d like to explore the link between bacteria and autism.

Do they think germs are responsible for autism? Not exactly, but alterations in gut bacteria have been linked to autism.

But first we need to understand what bacteria are and the role they play in the body. I know this may seem like simple stuff, but it’s important to understand that bacteria are more than just the “germs” you get warned about on adverts for cleaning products!

So what exactly are they?

Bacteria are teeny tiny organisms that live alongside humans and animals invisible to the human eye (but visible under a microscope). Most bacteria are harmless and play important roles like breaking down organic matter or are used in food and pharmaceutical production, but some can cause disease like chest infections, sepsis, chlamydia or stomach ulcers.

The human body is full of symbiotic bacteria living in a harmonious, mutually beneficial relationship. For example, Limosilactobacillus reuteri (known as Lactobacillus reuteri pre-2020) lives in your gut in a warm, stable environment feeding on dietary leftovers. In return, it interacts with our gut cells to stimulate them to secrete the chemical oxytocin which helps with social behaviours like bonding, trust and love, but also plays an important role in breastfeeding and uterine contractions. Win-win situation!

So where’sthe link with autism?

Studies have shown that autists have an altered gut microbiome (aka the bacterial zoo living in your intestines) vs neurotypicals wherein they have:

Lower levels of good bacteria like Bifidobacterium, Prevotella and Limosilactobacillus reuteri
Elevated levels of specific bacterial strains like Faecalibacterium, Clostridium, and Parabacteroides
Unbalanced levels of bacterial groups like Bacteroidetes and Firmicutes

Research has also linked specific strains to autism development. Citrobacter were more prevalent in infants who went on to develop autism, but the presence of Coprococcus was associated with a decreased likelihood of developing autism. So with all these bacterial alterations, it makes sense that bacteria might contribute to the development of autism.

However, some scientists have argued that these changes in the gut may be correlated to autistic diets which often prefer plain, highly processed foods. In addition, there has been backlash against the quality of evidence in autism and bacteria studies which have used poor statistics, small sample sizes, no placebos and have reported results that are difficult to reproduce. Basically, it’s bad science, with newer, larger, and placebo-controlled studies contradicting previous findings.

Hope you enjoyed this post dear Earthlings!

Have a lovely weekend!🙂

Aoife

August 14, 2026 1

Autism and Thrush

Greetings Earthlings! 🙂

Thrush- not the most fun topic to talk about, and not one that you would immediately associate with ASDs.

BUT!

This opportunistic infection may have more to do with autism than you might think!

Following a recent brush with thrush in my throat (cheers for that Ventolin! 😛 ), and being a super nerd who likes to understand their afflictions, through my reading I’ve discovered that candida infections in the gut are thought to contribute to the symptoms of autism.

So first things first, the basics- what is thrush?

For those of you fortunate enough to have not been infected at some point in your life, Candida is a type of yeast that usually exists in small colonies in the body, kept at bay by the immune system and our friendly neighbourhood symbiotic bacteria. However, when our immune system is run down, or after taking some forms of medication (such as antibiotics and steroid inhalers), this fungus can overgrow and cause a yeast infection (more commonly known as thrush). These infections for the majority of cases are mild and easy to treat, however more severe infections can be life threatening.

But how does this relate to autism?

In recent years, emerging evidence suggests that autists may have over double the amount of candida in their gut than their neurotypical peers. As we have discussed in my previous post exploring digestive issues in autism, the microbiota of the gut can play an important role in influencing brain development and behaviour. As such, it has been theorized that toxins such as ammonia released by yeast during infection may interfere with mental processing and induce autistic behaviours. Some doctors have reported improvements in autistic symptoms through the use of anti-fungal medication and candida diets (low sugar, anti-inflammatory diet purported to improve gut health); however, the vast majority of physicians remain skeptical about candida’s role in autism due to limited scientific evidence (at present).

So might there be a reason that autists are particularly prone to thrush infections?

Interestingly in my reading about pro-biotics (particular strains of live bacteria which can have beneficial effects for gut health such as in yogurts, supplements, pro-biotic drinks etc.) and their use against thrush, I discovered that the bacterium L. reuteri is thought to be one of the main gut defenders against a number of candida infections.

Now why does that name sound familiar?

In my post about digestive issues in autism we learned that this strain of lactobacillus is absent in some cases of autism. Moreover, some studies suggest that administering pro-biotics for L. reuteri to autists can improve behavioural symptoms, which would suggest that perhaps this bacterium, or lack there of, may predispose autists to thrush infections!

See? Far more interesting than you may have thought! 😉

Have a good weekend Earthlings! 🙂

Aoife

August 17, 2018 1

Autism 101- Digestive Problems

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.

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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? 😉

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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! 😉

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Aoife

February 17, 2017 26

Tag: bacteria

Autism and bacteria

Autism 101- Digestive Problems

A Is For Aoife Not Autism