Gut-Brain Connection in Autism

Gastrointestinal problems such as intestinal inflammation, leaky gut, poor digestive function, and frequent episodes of diarrhea or constipation are commonly experienced by children with autism ^{1, 2}.

Gut dysfunction is also linked to the absence of certain healthy bacterial strains that help digest food and fight harmful microorganisms. This often occurs because digestive issues that people with autism suffer from are frequently treated with antibiotics, and antibiotics kill certain types of beneficial bacteria ¹.

The loss of essential gut bacteria not only worsens digestive problems, but may also result in emotional disturbances, decreased mental performance, and abnormal neurotransmitter (brain messenger) activity due to the disruption of signals that travel from cells and bacteria in the gut to the brain ^{3, 4}. More specifically, unaddressed gastrointestinal problems negatively affect the gut-brain axis, which is an intricate connection between the intestinal environment and the brain ³.

Inadequate communication between the gut-brain axis is associated with the presence of autistic symptoms such as increased social avoidance, decreased time spent on social exploration and interactions, a reduced preference for social activity, poor memory function, and increased anxiety levels in response to stress ^{3, 4}. However, these types of behaviors tend to improve if the diet is supplemented with probiotics (healthy bacteria) regularly ^4-6.

This is because restoring the optimal balance of good bacteria in the gut enhances digestive function and this boosts mental performance in children with autism by re-establishing proper gut-brain axis communication ^{5, 6}.

Gut inflammation can also cause intestinal nerve damage. There are a number of intestinal nerves that facilitate learning, sustained focus, and emotion regulation, among other processes, by sending signals to the brain. If these nerves become inflamed or damaged, the onset or worsening of autistic symptoms such as psychosocial impairments, antisocial behavior, and anxiety may develop ^{1, 7}.

Furthermore, gut irritation and recurring digestive issues typically cause autistic children to favor certain types of foods and this can lead to nutritional deficiencies that worsen the balance of gut bacteria, increase intestinal inflammation, and prevent vital nutrients from reaching brain cells. All of these factors can exaggerate autistic symptoms due to the negative affect they can have on the brain-gut axis.

Therefore, it is important to address each of these areas in order to promote an enhanced quality of life for people with autism.

Overall, research has repeatedly demonstrated a link between gut-brain axis dysfunction and the degree of social impairment that an individual with autism may demonstrate ⁷. Fortunately, the combination of probiotics such as Lactobacillus, along with a diet that targets inflammation by reducing the intake of inflammatory foods, helps the intestinal tract heal and function properly ⁶.

This strategy has been shown to improve the digestive and cognitive issues that are associated with autism.

References

1. Molloy CA, Manning-Courtney P: Prevalence of chronic gastrointestinal symptoms in children with autism and autistic spectrum disorders. Autism. 2003;7(2):165-171.
2. Konstantynowicz J, Porowski T, et al. A potential pathogenic role of oxalate in autism. Eur J Paediatr Neurol. 2012;16(5):485-91.
3. Carabotti M, Scirocco A, et al. The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Ann Gastroenterol. 2015;28(2):203-209.
4. Mayer EA, Tillisch K, Gupta A. Gut/brain axis and the microbiota. J Clin Invest. 2015;125(3):926-38. 
5. Li Q, Han Y, et al. The gut microbiota and autism spectrum disorders. Front Cell Neurosci. 2017; 11: 120.
6. Li Q, Zhou JM. The microbiota-gut-brain axis and its potential therapeutic role in autism spectrum disorder. Neuroscience. 2016;324:131-9. 
7. Israelyan N, Margolis KG. Reprint of: Serotonin as a link between the gut-brain-microbiome axis in autism spectrum disorders. Pharmacol Res. 2019;140:115-120.