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