How your child’s gut affects their speech and development

If your child has speech delay or developmental concerns, you have likely been guided toward speech therapy or behavioral interventions.

However, an important piece of the puzzle that is often overlooked is the connection between the gut and the brain. Emerging research shows that the gut and brain are closely linked, and this relationship may be playing a significant role in how your child’s brain and speech is developing.

What is the gut-brain axis?

Information between the gut and brain travels in both directions, via the gut-brain axis. The enteric nervous system (ENS), often called the “second brain,” is a network of neurons in the gut that communicates with the central nervous system via the vagus nerve, while also receiving information from the brain. The ENS interacts closely with the immune system and gut microbiome to regulate gut function and brain signaling. 

The gut microbiome produces molecules which shape the development of the brain. This includes short chain fatty acids and tryptophan metabolites among others. These molecules are essential during the final three stages of children's brain development: the formation of synapses, the pruning of unused synapses, and myelination, which helps protect neurons.

Synapses are the connections between neurons, and facilitate the passing of information from one neuron to another. This impacts how we process information cognitively and on a sensory level, our social interactions, and our ability to store memory (as well as  many other functions). 

The majority of synapses are formed during the first two years of a baby’s life. Interestingly, the genes involved in the creation of new synapses are the same ones that contribute to the development of neurodiverse conditions. Scans performed by scientists on the brains of autistic individuals have suggested that those with the condition have too few, or too many synapses.

Our gut does much more than digest food. It plays a central role in brain development via the gut-brain axis.

Why the gut matters in speech delay

Children with speech delay commonly experience gastrointestinal symptoms such as constipation, diarrhea, bloating, and food sensitivities. These are not isolated issues, they likely reflect underlying imbalances that can influence the brain.

Research shows that in children with speech delay, the gut microbiome, immune system, and brain are closely connected and influence each other.

When the gut is imbalanced, several things can happen at the same time:

Increased inflammation: an unhealthy gut can activate the immune system and produce inflammatory signals that may affect how the brain processes information and develops language skills.

Changes in brain chemistry: gut bacteria produce important compounds that regulate neurotransmitters like serotonin and dopamine, which are involved in mood, attention, and communication. Imbalances in the gut can significantly disrupt your levels of these key neurotransmitters.

Altered microbial balance: studies have shown that neurodivergent children often have different gut bacteria compared to neurotypical children, and these differences may be linked to symptom severity.

Two-way communication between gut and brain: the gut and brain constantly send signals to each other. This means gut issues can affect behavior, and neurological differences can also affect digestion and gut function.

Rather than being separate issues, these processes are interconnected. This is why gut health can play an important role in a child’s overall development, including speech, behavior, and learning.

Supporting the brain alone may not be enough if underlying gut imbalances are present.

How gut bacterial byproducts influence social interaction, focus and speech

Gut bacteria produce metabolic byproducts when they break down food components such as fibre, fats, and proteins. These compounds can influence the enteric nervous system, immune system, and brain signalling pathways, which are important for social behaviour, attention, and language development.

Short-Chain Fatty Acids (SCFAs): Acetate, Propionate, Butyrate

SCFAs are produced through bacterial fermentation of dietary fiber.

• Butyrate supports gut barrier integrity and regulates your inflammatory response.
• Propionate, has many benefits, but when too elevated it can accumulate and excessive levels have been associated in research with altered neurotransmitter activity and increased neuroinflammatory signaling.
• Acetate influences energy metabolism and brain signaling.

These metabolites can affect the neurotransmitter systems involved in dopamine and serotonin regulation and the activity of immune cells in the central nervous system.

Lipopolysaccharides (LPS)

LPS are released during bacterial turnover or when gut barrier integrity is compromised.

They can trigger immune activation and inflammatory cytokine release, contributing to systemic inflammation and neuroinflammatory signaling.

D-Lactate and Organic Acids

Produced by certain bacterial fermentation processes, D-lactate and related organic acids may accumulate when you have too much bad bacteria in the gut..

They can influence mitochondrial energy production and neuronal signaling efficiency.

These bacterial metabolites do not act in isolation. Instead, they continuously shape immune activity, neural signaling, and brain energy metabolism. When balanced, they support stable communication between gut and brain networks; when imbalanced, they may contribute to variability in attention, social engagement, and speech development.

Identifying if gut health is playing a role

Common contributors to gut-brain disruption include microbiome imbalance, gastrointestinal inflammation, food sensitivities and microbial metabolites which affect the brain. Our tests can identify unknown food sensitivities, dysbiosis and your levels of inflammation.

The gut-brain axis provides a broader way to understand your child’s development. Speech delay and neurodivergent symptoms are not isolated to the brain, interconnected systems play a significant role.

Current research continues to support that the gut microbiome, immune system, and brain are closely linked, and this connection may influence developmental outcomes.

When balanced, gut health can support a healthy inflammatory response, improve nutrient availability, and support more consistent and regulated communication between neurons and brain networks related to attention, language, emotions and behaviour. 

References
G Sharon et al, Human gut microbiota from autism spectrum disorder promote behavioural symptoms in mice, 2019.
J F Cryan et al, The microbiota-gut-brain axis, 2019.
D-W Kang et al, Microbiota transfer therapy alters gut ecosystem and improves gastrointestinal and autism symptoms: an open-label study, 2017.
H E Vuong, E Y Hsiao, Emerging roles for the gut microbiome in autism spectrum disorder, 2017.
E A Mayer et al, Gut microbes and the brain: paradigm shift in neuroscience, 2014.
X Xing et al, Synaptic pruning mechanisms and application of emerging imaging techniques in neurological disorders, 2025.
P Washbourne, Synapse assembly and neurodevelopmental disorders, 2014.
B Kolb, R Gibb, Brain plasticity and behaviour in the developing brain, 2011.
G Marano et al, The paediatric microbiota-gut-brain axis: implications for neuropsychiatric development and intervention, 2025.
Columbia University Irving Medical Center, Children with autism have extra synapses in brain, 2014.
Yale School of Medicine, A key difference linked to autism is found for the first time in living people, 2024.