The Gut-Brain Axis in Dogs: The Impact of Nutrition

“The gut-brain axis governs the bidirectional conversation between your dog’s digestive system and their brain, with gut bacteria directly producing neurotransmitters like serotonin and dopamine that shape mood, behaviour, and cognitive function. While we cannot eliminate every source of stress or anxiety, we can profoundly influence the microbial ecosystem that manufactures neurochemicals and determines whether the brain receives signals of calm or distress.”

Summary

The canine gut-brain axis is a bidirectional communication network linking the gastrointestinal microbiome to the central nervous system through neural, hormonal, immune, and metabolic pathways. Over 90% of the body’s serotonin is produced in the gut, with beneficial bacteria playing essential roles in neurotransmitter synthesis, tryptophan metabolism, and GABA production — the neurochemicals that govern mood, anxiety, and stress resilience in dogs. Gut dysbiosis is clinically associated with anxiety disorders, aggression, compulsive behaviours, and accelerated cognitive decline, with anxious dogs consistently showing reduced populations of beneficial bacteria compared to behaviourally healthy controls. The gut-brain axis also underpins Canine Cognitive Dysfunction Syndrome, where gut-derived neuroinflammation and oxidative stress accelerate age-related brain pathology. Nutritional strategies targeting this axis — including psychobiotic probiotic strains, dietary tryptophan, adaptogenic herbs, omega-3 fatty acids, and prebiotic fibres — offer evidence-based tools for supporting canine mental health, stress resilience, and cognitive function across all life stages.

Why Your Dog’s Mental Health Begins in the Gut

When your dog trembles during thunderstorms, becomes destructive when left alone, or shows signs of confusion in their senior years, the instinct is to look to the brain for answers. Yet emerging science reveals that many of the answers lie not in the head, but in the gut. The gut-brain axis, a complex communication network linking the gastrointestinal tract to the central nervous system, has revolutionised our understanding of mental health in both humans and companion animals, offering new explanations for anxiety, cognitive decline, and behavioural disorders, along with promising new avenues for intervention.^1,3,8

The concept that gut health influences mental state is not entirely new; the phrases ‘gut feeling’ and ‘butterflies in the stomach’ acknowledge this connection in everyday language. However, the scientific understanding of the mechanisms involved has advanced dramatically in recent years. We now know that the gut houses its own nervous system containing hundreds of millions of neurons, produces the majority of the body’s mood-regulating neurotransmitters, and hosts a microbial ecosystem that actively communicates with the brain through multiple pathways.^1,7

For dog owners, this knowledge is transformative. It means that supporting your dog’s mental and emotional wellbeing extends beyond training and environmental management to encompass what goes into their food bowl. Nutritional strategies targeting the gut-brain axis can complement behavioural interventions for anxiety, potentially slow cognitive decline in ageing dogs, and help address challenging behaviours that have proven resistant to other approaches.^1,6,8 This guide provides the comprehensive understanding needed to apply gut-brain axis science to your dog’s benefit.

Key Takeaways

• The gut-brain axis is a bidirectional communication network operating through neural, hormonal, immune, and metabolic pathways, allowing gut microbes to directly influence brain function and behaviour whilst the brain simultaneously shapes gut microbial composition.^1,3,7
• Approximately 90-95% of the body’s serotonin, the neurotransmitter most associated with mood, calm, and wellbeing, is produced in the gut, with gut bacteria playing essential roles in its synthesis and regulation.^1,7
• The vagus nerve serves as the primary neural highway between gut and brain, transmitting signals in both directions and explaining why gut inflammation can trigger anxiety and why stress can cause digestive upset.^1,7
• Dogs with anxiety disorders consistently show altered gut microbiome compositions, with reduced populations of beneficial bacteria that produce calming neurotransmitter precursors and anti-inflammatory metabolites.^1,2,5,8
• Canine Cognitive Dysfunction (CCD), often called ‘doggy dementia’, shows strong associations with gut microbiome changes, neuroinflammation, and oxidative stress, all modifiable through nutritional intervention.^3,4
• Specific probiotic strains, termed ‘psychobiotics’, have demonstrated ability to reduce anxiety behaviours, improve stress resilience, and support cognitive function in dogs through gut-brain axis modulation.^1,8
• Tryptophan, the dietary precursor to serotonin, must be obtained from food and requires healthy gut bacteria for optimal conversion, explaining why gut dysbiosis can lead to mood and behavioural disturbances.^1,8
• Adaptogenic herbs like ashwagandha work synergistically with gut health support by regulating the hypothalamic-pituitary-adrenal (HPA) axis, reducing cortisol, and supporting stress resilience.¹
• A comprehensive approach combining prebiotics, probiotics, postbiotics, omega-3 fatty acids, calming botanicals, and supportive nutrients offers the most effective strategy for optimising gut-brain axis function and supporting canine mental health.^1,6,8

In This Guide

• What Is the Gut-Brain Axis and How Does It Work?
• How Gut Dysbiosis Drives Anxiety Disorders in Dogs
• How the Gut-Brain Axis Influences Cognitive Decline and Canine Dementia
• How Gut Health Shapes Aggression, Compulsive Behaviour, and Hyperactivity in Dogs
• Which Nutrients and Supplements Best Support the Canine Gut-Brain Axis?
• How Bonza’s Formulations Address the Gut-Brain Axis at Every Level
• How to Support Your Dog’s Gut-Brain Axis Through Nutrition
• Frequently Asked Questions
• Conclusion
• References
• Editorial Information

What Is the Gut-Brain Axis and How Does It Work?

The gut-brain axis encompasses the bidirectional communication network between the gastrointestinal tract and the central nervous system.^1,3,7 Far from being a simple one-way street where the brain controls gut function, this axis involves constant two-way signalling that allows gut conditions to profoundly influence brain activity, mood, and behaviour. Understanding these communication mechanisms reveals why gut health is inseparable from mental health.¹¹

The Enteric Nervous System: Why Your Dog’s Gut Has Its Own 600 Million Neurons

The gut possesses its own nervous system, the enteric nervous system (ENS), containing between 200 and 600 million neurons in dogs.¹ This extensive neural network has earned the gut the nickname ‘the second brain’ because it can operate independently of central nervous system input, controlling digestive processes through local reflexes. The ENS contains the same types of neurons and neurotransmitters found in the brain, including serotonin, dopamine, and GABA.^1,7 It processes sensory information from the gut environment, responds to mechanical and chemical stimuli, and coordinates the complex movements required for digestion. Importantly, the ENS communicates extensively with the brain, sending far more signals upward than it receives downward, meaning gut conditions constantly inform brain function.¹

How the Gut and Brain Communicate: Neural, Hormonal, Immune, and Metabolic Pathways

The gut and brain communicate through multiple interconnected pathways:^1,3,7

The vagus nerve: This major cranial nerve serves as the primary neural highway between gut and brain, with approximately 80% of its fibres carrying signals from gut to brain rather than the reverse.^1,7 The vagus nerve transmits information about gut distension, inflammation, microbial metabolites, and nutrient content directly to brain regions controlling mood, stress response, and cognition. Vagal tone, the activity level of this nerve, correlates with stress resilience and emotional regulation.¹

The immune system: The gut houses approximately 70% of the body’s immune cells.¹ When gut inflammation occurs, immune signals including cytokines can reach the brain through the bloodstream, potentially triggering neuroinflammation that affects mood and cognition.^1,3 This immune pathway helps explain why gut dysbiosis can manifest as depression, anxiety, or cognitive impairment.^1,8

The hypothalamic-pituitary-adrenal (HPA) axis: This hormonal system governs the stress response, controlling cortisol release.¹ Gut microbiome composition influences HPA axis activity, with dysbiosis often associated with exaggerated stress responses and elevated cortisol levels.^1,8 Conversely, chronic stress affects gut permeability and microbiome composition, creating potential feedback loops.¹

Microbial Metabolites: The Molecules That Connect Gut to Brain

Beyond neural, immune, and hormonal pathways, gut bacteria communicate with the brain through an extensive repertoire of bioactive compounds that enter circulation and directly influence neurological function.^1,6 Among these, short-chain fatty acids (SCFAs), particularly butyrate and propionate, serve as primary molecular messengers. Produced when bacteria ferment dietary fibre, these metabolites can cross the blood-brain barrier and modulate neuroinflammation, neurotransmitter production, and neural plasticity.^1,6,7,12

The scale of this communication system became dramatically clearer with the Waltham Petcare Science Institute’s landmark 2026 genome catalogue of the canine gut microbiome, the most comprehensive mapping of its kind.⁹ The study revealed that nearly 38% of all bacterial species identified possess the genetic machinery for butyrate production, and these species represent 45.6% of the microbiome by total abundance.⁹ For propionate, 18.8% of species showed production capacity.⁹ In other words, almost half of the healthy canine gut microbiome, measured by abundance, is dedicated to producing the very molecules that signal to the brain.Perhaps most remarkably, the two most abundant newly discovered species in the catalogue, Candidatus Skylacomonas catulintestiniplasma (comprising 7.3% of the microbiome) and Candidatus Ileibacterium canenteradaptatus (5.7%), are both enriched for butyrate production pathways.⁹ These bacteria, previously unknown to science, appear to be core members of the healthy canine gut, and their prominence underscores butyrate production as a defining feature of a well-functioning microbiome.⁹

Other bacterial metabolites extend this communication further, with some capable of mimicking or modulating neurotransmitter activity directly.^1,6 But the Waltham findings highlight a critical point for dog owners: when we support the gut microbiome through nutrition, through prebiotic fibre, probiotics, and a diet rich in fermentable substrates, we are directly influencing the molecular signals that reach our dogs’ brains, shaping mood, cognition, and emotional resilience from the inside out.^6,9

How Gut Bacteria Produce and Regulate Your Dog’s Key Neurotransmitters

Perhaps the most striking aspect of gut-brain communication is the gut’s role in neurotransmitter production:^1,7

Serotonin: Approximately 90-95% of the body’s serotonin is produced in the gut by enterochromaffin cells, with gut bacteria playing essential roles in regulating its synthesis.^1,7 Serotonin influences mood, anxiety, sleep, appetite, and pain perception. Whilst gut-produced serotonin does not directly enter the brain (it cannot cross the blood-brain barrier), it affects brain function through vagal nerve signalling and influences on immune function.¹

GABA (gamma-aminobutyric acid): This primary inhibitory neurotransmitter promotes calm and reduces anxiety.^1,8 Certain gut bacteria, particularly Lactobacillus and Bifidobacterium species, can produce GABA directly.^1,8 GABA-producing bacteria are associated with reduced anxiety behaviours in animal studies.¹

Dopamine: Involved in motivation, reward, and movement, approximately 50% of the body’s dopamine is produced in the gut.¹ Gut bacteria influence dopamine synthesis and metabolism, potentially affecting motivation, learning, and behavioural responses.^1,8

Tryptophan metabolism: Tryptophan, an essential amino acid obtained from diet, serves as the precursor for serotonin synthesis.¹ Gut bacteria significantly influence tryptophan availability and metabolism.^1,6,12 Some bacteria compete for tryptophan, whilst others facilitate its conversion to serotonin or redirect it toward other metabolic pathways. Gut dysbiosis can therefore directly affect the building blocks available for mood-regulating neurotransmitter production.^1,8

How Microbiome Composition Directly Influences Your Dog’s Brain Function and Behaviour

The gut microbiome, the collective community of bacteria, fungi, viruses, and other microorganisms inhabiting the gastrointestinal tract, actively participates in gut-brain communication.^1,6 Different bacterial species influence brain function in different ways: some produce neurotransmitters or their precursors; others generate metabolites that cross the blood-brain barrier; still others modulate immune responses that affect neuroinflammation.^1,6,7 The composition of your dog’s microbiome therefore directly influences their mental state and cognitive capacity.^1,2,8 Germ-free animals (raised without microbiomes) show profound abnormalities in brain development, neurotransmitter levels, and behaviour, demonstrating that microbial input is essential for normal brain function.^1,3 Fortunately, microbiome composition is highly modifiable through diet, making it a promising target for supporting canine mental health.⁶

How Gut Dysbiosis Drives Anxiety Disorders in Dogs

Dogs with anxiety disorders consistently show altered gut microbiome compositions, with reduced populations of beneficial bacteria that produce calming neurotransmitters — a finding that directly links gut dysbiosis to the maintenance and amplification of anxiety.^1,8 Whilst behavioural modification and, in severe cases, pharmaceutical intervention remain important management tools, the gut-brain axis offers additional understanding of anxiety’s origins and new opportunities for nutritional support.¹

Which Types of Canine Anxiety Are Linked to Gut-Brain Axis Dysfunction?

Canine anxiety manifests in various forms, each potentially influenced by gut-brain axis dysfunction:^1,8

Separation anxiety: Distress when separated from owners, manifesting as destructive behaviour, vocalisation, house soiling, or escape attempts. This common condition reflects an overactive stress response that may be exacerbated by gut dysbiosis and HPA axis dysregulation.^1,8

Noise phobias: Intense fear responses to sounds such as thunderstorms, fireworks, or construction noise. Dogs with noise phobias often show heightened overall anxiety and may have altered stress hormone regulation.¹

Generalised anxiety: Persistent, pervasive anxiety not tied to specific triggers. Affected dogs may appear constantly vigilant, startle easily, and struggle to relax even in safe environments.^1,8

Social anxiety: Fear or discomfort around unfamiliar people or dogs. This may develop from insufficient socialisation but can be maintained by neurobiological factors including gut-brain axis dysfunction.¹

Travel anxiety: Stress associated with car journeys, veterinary visits, or novel environments. The combination of motion, confinement, and unfamiliarity can trigger significant stress responses.¹

How Gut Dysbiosis Contributes to Anxiety

Research consistently demonstrates that dogs with anxiety disorders show altered gut microbiome compositions compared to behaviourally normal dogs.^1,2,5,8 Anxious dogs typically have reduced populations of beneficial bacteria including Lactobacillus and Bifidobacterium species known to produce calming neurotransmitters and anti-inflammatory metabolites.^1,5,8,14 They may show increased populations of potentially pathogenic bacteria that promote inflammation.^5,8 This dysbiosis affects anxiety through multiple mechanisms: reduced GABA and serotonin precursor production; increased inflammatory signalling reaching the brain via immune pathways; compromised vagal nerve signalling; and HPA axis dysregulation leading to elevated cortisol.^1,8

The Waltham Petcare Science Institute’s 2026 genome catalogue quantifies precisely what is at stake when this microbial balance is disrupted.⁹ In healthy dogs, 45.6% of the microbiome by abundance is dedicated to butyrate production, the very metabolite that supports gut barrier integrity, dampens neuroinflammation, and modulates signalling along the gut-brain axis.⁹ Disruption of these SCFA-producing populations has already been linked to chronic enteropathy in dogs, and the Waltham data suggests the implications extend well beyond the gut.⁹ Any significant shift in butyrate-producing bacteria could fundamentally alter the molecular signals reaching the brain, immune system, and other organs, potentially reinforcing the anxiety-dysbiosis cycle rather than simply accompanying it.^1,9

Importantly, these microbial alterations may not merely accompany anxiety but actively contribute to its maintenance, creating a self-perpetuating cycle.^1,2,5

How Stress and Gut Dysbiosis Reinforce Each Other in a Self-Perpetuating Cycle

The relationship between stress and gut health operates as a vicious feedback loop.¹ When a dog experiences stress, the resulting cortisol release and sympathetic nervous system activation directly affect gut function: blood flow to the digestive tract decreases, gut motility changes, intestinal permeability increases (‘leaky gut’), and the environment becomes less hospitable to beneficial bacteria.^1,8 These gut changes then feed back to the brain through the pathways described above, potentially increasing anxiety and stress sensitivity.¹ This explains why acute stressors can have lasting effects on anxiety levels, the gut disruption they cause persists and continues signalling distress to the brain long after the original stressor has passed.^1,8 Breaking this cycle requires addressing both the psychological and physiological components, with gut health support playing a crucial role.¹

However, evidence on stress-induced dysbiosis is more nuanced than early studies suggested. A 2024 Waltham Petcare Science Institute study by Patel and colleagues exposed twenty healthy adult dogs to repeated acute stress events (car travel, separation) and found no significant changes in faecal quality, pH, or microbiota composition, despite measurable physiological stress responses. This indicates that healthy dogs with established gut microbiome diversity may have meaningful resilience to short-term stress, whereas dysbiosis appears more strongly associated with chronic anxiety states or pre-existing microbiome imbalance.¹⁰^,¹³

Which Nutritional Interventions Help Break the Anxiety-Dysbiosis Cycle?

Breaking the anxiety-dysbiosis cycle requires addressing both ends of the feedback loop simultaneously — the gut environment that generates distress signals, and the neurochemical pathways through which those signals amplify anxiety. No single ingredient achieves this. The evidence supports a multi-layered nutritional approach in which each component targets a distinct mechanism within the cycle.¹˒⁸

The five primary intervention targets are: restoring beneficial bacterial populations to support calming neurotransmitter production; supplying tryptophan as the dietary substrate for serotonin synthesis; supporting GABA receptor function through magnesium and B vitamin cofactors; reducing gut-derived neuroinflammation through omega-3 fatty acids; and regulating the HPA axis stress response through adaptogenic herbs.¹˒⁸ Together, these strategies work on the microbiome, the neurotransmitter synthesis pathways, and the hormonal stress response that perpetuates the cycle — rather than addressing any one component in isolation.

For full detail on each ingredient, the evidence behind specific strains and nutrients, and how they interact within a complete gut-brain axis protocol, see Which Nutrients and Supplements Best Support the Canine Gut-Brain Axis? below.

How the Gut-Brain Axis Influences Cognitive Decline and Canine Dementia

The gut microbiome directly influences neuroinflammation, oxidative stress, and the accumulation of beta-amyloid plaques associated with Canine Cognitive Dysfunction Syndrome, making gut health a modifiable factor in the rate of brain ageing.³ The gut-brain axis plays a significant role in brain ageing and neurodegenerative processes, offering opportunities for nutritional intervention to support cognitive function throughout the lifespan and potentially slow age-related decline.^3,4

What Is Canine Cognitive Dysfunction Syndrome and How Does the Gut Contribute?

Canine Cognitive Dysfunction Syndrome (CCD), sometimes called ‘doggy dementia’, affects a significant proportion of senior dogs.³ Studies suggest that over 60% of dogs aged 11-16 years show at least one sign of cognitive impairment.³ The condition shares many features with human Alzheimer’s disease, including beta-amyloid plaque accumulation in the brain.^3,¹⁵

Common signs include:

Disorientation: Getting lost in familiar environments, staring into space, appearing confused about location or direction.³

Altered interactions: Changes in social behaviour, reduced interest in interaction, failure to recognise familiar people or pets.³

Sleep-wake cycle changes: Sleeping more during the day, restlessness or vocalisation at night, disrupted circadian rhythms.³

House soiling: Loss of previously reliable house training, eliminating in inappropriate locations.³

Activity changes: Decreased activity and interest in play, aimless wandering, repetitive behaviours.³

How Gut Dysbiosis Promotes Neuroinflammation and Accelerates Brain Ageing in Dogs

Research increasingly links gut microbiome changes to neurodegenerative processes.^3,4 Ageing dogs show declining microbiome diversity, with reduced populations of beneficial bacteria and increased potentially pathogenic species.^4,6 This dysbiosis promotes systemic inflammation, including neuroinflammation, chronic low-grade inflammation in the brain that damages neurons and accelerates cognitive decline.³ Inflammatory signals from the gut reach the brain through immune pathways and a more permeable blood-brain barrier (which itself can result from gut-derived inflammation).^3,7 Studies in humans and animal models demonstrate that individuals with cognitive impairment consistently show microbiome alterations, and that these changes may precede and contribute to, rather than merely result from, brain pathology.³

How Oxidative Stress Damages the Ageing Canine Brain — and the Gut’s Role in It

The brain is particularly vulnerable to oxidative stress due to its high metabolic rate, abundant lipid content, and relatively limited antioxidant defences.³ Oxidative damage to brain cells accumulates with age and contributes to cognitive decline.³ The gut microbiome influences systemic oxidative stress levels: beneficial bacteria produce antioxidant compounds, whilst dysbiosis can increase oxidative stress through inflammatory processes.^3,6 Short-chain fatty acids produced by healthy gut bacteria have demonstrated neuroprotective effects, reducing oxidative damage and supporting mitochondrial function in brain cells.^3,6

The Waltham Petcare Science Institute’s 2026 genome catalogue revealed the remarkable extent of this protective capacity: nearly 38% of all canine gut bacterial species possess butyrate production pathways, representing 45.6% of the microbiome by abundance, meaning that in a healthy gut, almost half the microbial community is actively generating neuroprotective metabolites.⁹

Supporting gut health therefore offers an indirect route to reducing brain oxidative stress.^3,6

Which Nutritional Strategies Help Protect Your Dog’s Brain from Age-Related Decline?

Nutritional strategies can support cognitive health through gut-brain axis modulation:³

DHA omega-3: DHA constitutes a major structural component of brain cell membranes. Adequate DHA intake supports neuronal integrity, synaptic function, and neuroplasticity. Studies demonstrate that DHA supplementation can improve cognitive function in senior dogs.³

Antioxidant support: Vitamins C and E, along with plant polyphenols, help combat oxidative damage. Antioxidant-enriched diets have shown benefit for cognitive function in ageing dogs.³

Microbiome support: Maintaining microbiome diversity through prebiotic and probiotic intake supports anti-inflammatory SCFA production and reduces neuroinflammation.^3,6

B vitamin complex: B vitamins support neurological function, neurotransmitter synthesis, and energy metabolism in brain cells. B12 deficiency is particularly associated with cognitive impairment.³

Medium-chain triglycerides (MCTs): MCTs provide ketones, an alternative brain fuel that may benefit cognition in dogs with age-related glucose metabolism changes.³

How Gut Health Shapes Aggression, Compulsive Behaviour, and Hyperactivity in Dogs

Aggression, compulsive behaviours, and hyperactivity in dogs all show documented associations with gut microbiome composition through the neurotransmitter pathways the gut controls — particularly serotonin and dopamine.^2,8 Understanding these connections opens additional avenues for supporting dogs with challenging behaviours.

How Gut-Mediated Serotonin Deficiency Contributes to Aggression and Impulsivity in Dogs

Serotonin plays a crucial role in impulse control and the regulation of aggressive behaviour.^5,8 Low serotonin levels are consistently associated with increased aggression across species.^5,8 Given the gut’s central role in serotonin metabolism and the influence of gut bacteria on tryptophan availability (serotonin’s precursor), gut dysbiosis may contribute to impaired impulse control and heightened aggression in some dogs.^5,8,14 Research has demonstrated that dietary tryptophan supplementation can reduce territorial aggression in dogs, supporting the connection between gut-mediated neurotransmitter metabolism and behavioural regulation.^5,8 Dogs with aggression issues may benefit from dietary strategies supporting serotonin production alongside appropriate behavioural management.^5,8

How Gut-Brain Axis Dysfunction May Drive Compulsive Behaviours in Dogs

Canine compulsive disorders, including tail chasing, shadow chasing, flank sucking, and excessive licking, involve repetitive behaviours that interfere with normal function.⁸ These conditions share features with human obsessive-compulsive disorder (OCD), which has documented associations with gut microbiome alterations.⁸ Compulsive behaviours in dogs may reflect underlying anxiety or neurological imbalances in which gut-brain axis dysfunction plays a role.⁸ Supporting gut health and neurotransmitter balance through nutrition may complement behavioural therapy for dogs with compulsive disorders, though these conditions typically require comprehensive professional management.⁸

How Gut-Derived Dopamine Dysregulation Contributes to Hyperactivity in Dogs

Some dogs display persistent hyperactivity, difficulty settling, and apparent attention deficits that may parallel aspects of human ADHD.⁸ Dopamine and norepinephrine, neurotransmitters central to attention and impulse control, are influenced by gut microbiome composition.^1,8 Gut-produced metabolites can affect dopamine synthesis and signalling, potentially influencing activity levels and attention capacity.^1,8 Dietary interventions supporting balanced neurotransmitter function, including adequate protein intake for amino acid supply, B vitamins for neurotransmitter synthesis, and omega-3s for brain cell membrane function, may help support calmer, more focused behaviour alongside appropriate training and environmental management.⁸

How Diet Shapes Canine Behaviour Through Gut-Brain Axis Pathways

Diet affects behaviour through multiple gut-brain pathways:^2,6,8

Protein quality and amino acid balance: Adequate intake of tryptophan, tyrosine, and other amino acid neurotransmitter precursors supports balanced brain chemistry. Protein quality affects amino acid availability.⁸

Blood sugar stability: Diets causing blood sugar fluctuations may contribute to mood and energy instability. Complex carbohydrates with fibre support more stable blood glucose.⁸

Food sensitivities: Unidentified food sensitivities can cause gut inflammation that signals to the brain, potentially affecting mood and behaviour.⁸ Elimination diets may help identify problematic ingredients.

Gut microbiome effects: Different dietary patterns support different microbial populations with varying effects on brain function.^2,6 Fibre intake, protein sources, and the presence of prebiotic and probiotic ingredients all influence microbiome-mediated behavioural effects.^6,8

Which Nutrients and Supplements Best Support the Canine Gut-Brain Axis?

The modifiability of the gut microbiome through diet makes nutritional intervention a powerful tool for supporting gut-brain axis function.⁶ A comprehensive approach combines multiple strategies to optimise microbial balance, neurotransmitter production, and the various communication pathways linking gut to brain.^1,6,8

How Prebiotics Support Brain Health by Nourishing Beneficial Gut Bacteria

Prebiotics, non-digestible compounds that selectively nourish beneficial gut bacteria, support brain health indirectly by promoting populations of bacteria with positive gut-brain effects:⁶

Fructooligosaccharides (FOS): Found naturally in chicory root and other plants, FOS promotes Bifidobacterium growth, associated with reduced anxiety and improved mood in research studies.^6,8

Inulin: A longer-chain fructan that serves as food for beneficial bacteria throughout the colon, supporting diverse SCFA-producing populations.⁶

Mannan-oligosaccharides (MOS): Derived from yeast cell walls, MOS binds to pathogenic bacteria preventing their colonisation whilst supporting beneficial microbes.⁶

Beta-glucans: These prebiotic fibres modulate immune function and support anti-inflammatory responses that protect against neuroinflammation.⁶

Which Probiotic Strains Have Demonstrated Mental Health Benefits in Dogs?

The term ‘psychobiotics’ describes probiotics that confer mental health benefits when consumed.^1,8 Research has identified several strains with demonstrated effects on mood, anxiety, and cognitive function:

Lactobacillus helveticus: One of the most extensively studied psychobiotics, L. helveticus has demonstrated ability to reduce anxiety-like behaviours, lower cortisol levels, and improve stress resilience in multiple studies.^1,8 It may work partly through GABA production and HPA axis modulation.¹ L. helveticus is considered an anxiolytic probiotic strain.¹

Lactobacillus rhamnosus: Research shows this probiotic strain can reduce anxiety and depression-like behaviours, with effects dependent on intact vagal nerve signalling, demonstrating the neural pathway’s importance.^1,8

Bifidobacterium longum: Associated with reduced stress responses and improved cognitive function.^1,8 This species produces compounds that influence brain function through multiple pathways.¹

Bacillus velezensis (Calsporin®): A spore-forming probiotic that survives digestive transit reliably, supporting overall gut health and microbiome balance that underpins gut-brain axis function.⁶

Bonza’s Bliss Bioactive Bites delivers the psychobiotic Lactobacillus helveticus HA-122 at 2.25 × 10⁹ CFU per serving alongside Calsporin® as the spore-forming probiotic foundation, combining both strains within the Biotics Triad framework to address the gut-brain axis at multiple levels simultaneously.

How Postbiotics Deliver Gut-Brain Benefits Without Relying on Live Bacterial Survival

Postbiotics, the beneficial metabolites or non-viable components of probiotic bacteria, offer a way to deliver gut-brain benefits without requiring live organisms to survive and colonise.⁶ This is particularly valuable given individual microbiome variability and the challenges of maintaining probiotic viability through food processing and gastric transit. Postbiotics can include heat-killed bacterial cells that still signal to the immune system, fermentation products containing beneficial metabolites, and bacterial cell wall components with bioactive properties.⁶ For dogs with compromised gut health or those who have not responded to probiotic supplementation, postbiotics may provide more consistent benefits.⁶

Which Nutrients Are Essential for Neurotransmitter Production in Dogs?

Several nutrients serve as essential building blocks or cofactors for neurotransmitter production:¹

Tryptophan: This essential amino acid cannot be synthesised and must be obtained from diet. It serves as the sole precursor for serotonin and melatonin.¹ Supplementation has demonstrated calming effects and improved stress resilience in dogs.^1,8 Bliss Bioactive Bites provides L-tryptophan at 63mg per two chews, formulated as a therapeutic dose alongside the B vitamin cofactors required for its conversion to serotonin, recognising that tryptophan availability alone is insufficient without the enzymatic support the conversion pathway requires.

B vitamins: B6 (pyridoxine) is essential for converting tryptophan to serotonin and tyrosine to dopamine.¹ B12 supports neurological function and cognitive health.³ B1, B2, and B5 support energy metabolism in neurons.¹

Magnesium: This mineral supports GABA receptor function, promotes relaxation, and is often depleted during chronic stress.¹ Magnesium glycinate offers excellent bioavailability and additional calming properties from the glycine component.¹

Zinc: Required for neurotransmitter synthesis and release, zinc also supports gut barrier integrity.¹ Chelated forms like zinc glycinate offer superior absorption.¹

Taurine: This amino acid supports neurological function, acts as a neuromodulator, and helps regulate stress responses.¹ It is considered conditionally essential for dogs and beneficial for brain health.¹

How DHA and EPA Support Brain Structure and Reduce Neuroinflammation in Dogs

DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) support brain health through multiple mechanisms.^3,¹⁵ DHA comprises a significant portion of brain cell membrane phospholipids, maintaining membrane fluidity essential for neurotransmitter receptor function and signal transmission.³ EPA exerts potent anti-inflammatory effects, helping reduce neuroinflammation associated with anxiety, cognitive decline, and behavioural disorders.³ Both omega-3s influence gene expression affecting neuroplasticity and neuroprotection.³ Studies demonstrate that omega-3 supplementation can improve learning, reduce anxiety behaviours, and support cognitive function in dogs.³ Algae-derived sources provide DHA directly in its most bioavailable form.

How Adaptogens and Calming Herbs Support HPA Axis Regulation and Stress Resilience

Certain herbs offer additional support for gut-brain axis function and stress resilience:⁸

Ashwagandha (Withania somnifera): This adaptogenic herb helps regulate the HPA axis, reducing cortisol levels and improving stress resilience.^1,8 It has demonstrated anxiolytic effects comparable to some pharmaceutical agents without sedation.⁸

Passionflower (Passiflora incarnata): Contains compounds that enhance GABA activity in the brain, promoting calm without drowsiness.⁸ Particularly effective for acute anxiety situations.⁸

Lemon balm (Melissa officinalis): This calming herb inhibits GABA-transaminase, the enzyme that breaks down GABA, effectively increasing GABA availability.⁸ It has mild sedative properties useful for anxiety relief.⁸

L-theanine (from green tea): This amino acid crosses the blood-brain barrier and promotes alpha brain wave activity associated with relaxed alertness.⁸ It increases GABA, serotonin, and dopamine whilst reducing cortisol.⁸

Chamomile (Matricaria chamomilla/recutita): Contains apigenin, which binds to GABA receptors producing mild sedative and anxiolytic effects.⁸ Also supports digestive comfort, addressing both ends of the gut-brain axis.⁸

Within the Bonza “One Gut. Whole Dog.” formulation framework, ashwagandha is included in the PhytoPlus® blend in Superfoods & Ancient Grains and as ashwagandha oil (60mg) in Bliss Bioactive Bites, addressing HPA axis regulation as a core component of gut-brain axis support rather than an optional addition.

The SCFA signalling pathways that connect gut fermentation to brain function are the same pathways driven by fibre-rich plant-based diets in dogs. Direct behavioural-outcome trials on plant-based canine diets remain to be conducted, but the mechanistic chain is well characterised. For the full peer-reviewed evidence on plant-based canine nutrition and the SCFA biology that underpins the gut-brain axis, see the Bonza evidence review on plant-based dog food research.

How Bonza’s Formulations Address the Gut-Brain Axis at Every Level

Both Bonza’s Superfoods & Ancient Grains and Bliss Bioactive Bites are formulated to address the gut-brain axis directly, combining psychobiotics, tryptophan, adaptogens, and the full Biotics Triad to support neurotransmitter production, HPA axis regulation, and microbiome balance simultaneously.. The gut-brain axis is one of the eight gut-organ axes underpinning Bonza’s formulation framework, informing both Superfoods & Ancient Grains and the Bioactive Bites supplement range. The daily food provides foundational gut-brain axis support through Calsporin®, TruPet™ postbiotic, prebiotic chicory, DHAgold® algae-derived omega-3, and the PhytoPlus® botanical blend including ashwagandha, working together through the Biotics Triad to maintain the microbiome balance, SCFA production, and HPA axis regulation that healthy brain signalling depends on.

For dogs requiring targeted gut-brain axis support, Bliss Bioactive Bites is formulated specifically for this axis, combining the psychobiotic Lactobacillus helveticus at 2.25 × 10⁹ CFU, L-tryptophan as serotonin precursor, ashwagandha oil for cortisol regulation, passionflower and lemon balm for GABA pathway support, and magnesium glycinate for nervous system function. Used together with Superfoods & Ancient Grains, Bliss addresses the gut-brain axis at both ends simultaneously, from the microbial foundation of neurotransmitter production to the hormonal stress responses it regulates.

How to Support Your Dog’s Gut-Brain Axis Through Nutrition

Frequently Asked Questions

Conclusion

The gut-brain axis represents a paradigm shift in how we understand canine mental health.^1,3 The discovery that the gut functions as a ‘second brain’, housing its own nervous system, producing the majority of the body’s mood-regulating neurotransmitters, and hosting microbial communities that actively communicate with the central nervous system, reveals why mental and emotional wellbeing cannot be separated from digestive health.^1,7 For dogs struggling with anxiety, cognitive decline, or challenging behaviours, this connection offers both explanation and hope.^1,3,8

Anxiety disorders, neurodegenerative conditions like Canine Cognitive Dysfunction, and behavioural problems including aggression and compulsive behaviours all show associations with gut microbiome alterations.^1,2,3,5,8 The stress-gut-brain feedback loop explains how acute stressors can have lasting effects, whilst the neuroinflammation associated with dysbiosis contributes to cognitive decline.^1,3 Understanding these mechanisms transforms gut health support from general wellness advice into targeted therapeutic strategy.^1,8

Nutritional modulation of the gut-brain axis offers powerful tools for supporting canine mental health.^1,6,8 Psychobiotic probiotics can reduce anxiety and improve stress resilience.^1,8 Tryptophan ensures adequate substrate for serotonin synthesis.¹ Adaptogenic herbs regulate the hormonal stress response.⁸ Omega-3 fatty acids support brain structure and reduce neuroinflammation.³ Prebiotics and postbiotics maintain the microbial balance underlying healthy gut-brain communication.⁶ Combined thoughtfully, these strategies can complement behavioural training, environmental management, and veterinary treatment to help dogs achieve their best mental and emotional wellbeing.^1,2,8

As our understanding of the gut-brain axis continues to advance, we can expect increasingly sophisticated approaches to supporting canine mental health through nutrition. The recognition that what goes into the food bowl influences what happens in the brain empowers dog owners to take meaningful action for their companions’ psychological welfare, one meal, one supplement, one thoughtful nutritional choice at a time.

Explore the Gut-Organ Axes

• The Gut-Oral Axis in Dogs – The Health Implications
• The Dog Gut Microbiome: Vital Key to Dog Health
• Canine Gut-Organ Axes: How Gut Health Shapes Skin, Joints, Brain, and More
• The Gut-Skin Axis in Dogs: Why Skin Problems Start in the Gut
• The Gut-Joint Axis in Dogs – Nutritional Impact on Mobility
• The Gut-Metabolic Axis in Dogs – Powerful Health Regulator
• The Gut-Liver Axis in Dogs – Supporting Vital Detoxification
• The Gut-Heart Axis in Dogs: Nutritional Strategies for Cardiovascular Health
• The Gut-Longevity Axis in Dogs: Key To Improved Healthspan
• Best Gut Health Supplement for Dogs in 2026: A Canine Nutritionist’s Comparative Evaluation
• Gut Health Supplements for Dogs: Why Probiotics Alone Are Not Enough
• Best Probiotics for Dogs: A Canine Nutritionist’s Guide to Real Gut Impact
• From Skin to Joints to Mood: Which Gut Supplement Does Your Dog Actually Need?

References

1. Sacoor, Carina et al. “Gut-Brain Axis Impact on Canine Anxiety Disorders: New Challenges for Behavioral Veterinary Medicine.” Veterinary medicine international vol. 2024 2856759. 23 Jan. 2024, doi:10.1155/2024/2856759

2. Agnese Crisante, Fiona Newberry, Simon R. Clegg, Gabriella L. Mitchell, Thomas W. Pike, Vicky Ratcliffe, Adele Spain, Anna Wilkinson, Helen Zulch, Daniel S. Mills, A critical review of research concerning the gut microbiome in dogs and its relationship with behaviour, Applied Animal Behaviour Science, Volume 292, 2025, 106755, ISSN 0168-1591, doi.org/10.1016/j.applanim.2025.106755

3. Ambrosini, Yoko M et al. “The Gut-Brain Axis in Neurodegenerative Diseases and Relevance of the Canine Model: A Review.” Frontiers in aging neuroscience vol. 11 130. 18 Jun. 2019, doi:10.3389/fnagi.2019.00130

4. Fernández-Pinteño, A., Pilla, R., Suchodolski, J., Apper, E., Torre, C., Salas-Mani, A., & Manteca, X. (2025). Age-Related Changes in Gut Health and Behavioral Biomarkers in a Beagle Dog Population. Animals, 15(2), 234. https://doi.org/10.3390/ani15020234

5. Pellowe, S.D., Zhang, A., Bignell, D.R.D. et al. Gut microbiota composition is related to anxiety and aggression scores in companion dogs. Sci Rep 15, 24336 (2025). https://doi.org/10.1038/s41598-025-06178-4

6. Pilla, Rachel et al. The Gut Microbiome of Dogs and Cats, and the Influence of Diet. Veterinary Clinics: Small Animal Practice, Volume 51, Issue 3, 605–621 DOI: 10.1016/j.cvsm.2021.01.002

7. Gernone, Floriana et al. “Role of Gut Microbiota through Gut-Brain Axis in Epileptogenesis: A Systematic Review of Human and Veterinary Medicine.” Biology vol. 11,9 1290. 30 Aug. 2022, doi:10.3390/biology11091290

8. Kiełbik P, Witkowska-Piłaszewicz O. The Relationship between Canine Behavioral Disorders and Gut Microbiome and Future Therapeutic Perspectives. Animals. 2024; 14(14):2048. https://doi.org/10.3390/ani14142048

9. Castillo-Fernandez J, Gilroy R, Jones RB, Honaker RW, Whittle MJ, Watson P, Amos GCA. Waltham catalogue for the canine gut microbiome: a complete taxonomic and functional catalogue of the canine gut microbiome through novel metagenomic based genome discovery. Microbiome. 2026 Jan 17;14(1):25. doi: 10.1186/s40168-025-02265-w. PMID: 41547860; PMCID: PMC12811905.

10. Patel KV, Hunt ABG, Castillo-Fernandez J, Abrams C, King T, Watson P, Amos GCA. Impact of acute stress on the canine gut microbiota. Sci Rep. 2024 Aug 14;14:18897. doi: 10.1038/s41598-024-66652-3. PMID: 39143138. PMC: PMC11324789.

11. Luca M, Chattipakorn SC, Sriwichaiin S, Luca A. Cognitive-Behavioural Correlates of Dysbiosis: A Review. Int J Mol Sci. 2020 Jul 8;21(14):4834. doi: 10.3390/ijms21144834. PMID: 32650553. PMC: PMC7402132.

12. Pilla R, Suchodolski JS. The Role of the Canine Gut Microbiome and Metabolome in Health and Gastrointestinal Disease. Front Vet Sci. 2020 Jan 14;6:498. doi: 10.3389/fvets.2019.00498. PMID: 31993446. PMC: PMC6971114.

13. Kim H, Lee S, Lee Y. Understanding the diversity and roles of the canine gut microbiome. J Anim Sci Biotechnol. 2025 Jul 7;16(1):95. doi: 10.1186/s40104-025-01235-4. PMID: 40615864. PMC: PMC12228404.

14. Mondo E, Barone M, Soverini M, D’Amico F, Cocchi M, Petrulli C, Mattioli M, Marliani G, Candela M, Accorsi PA. Gut microbiome structure and adrenocortical activity in dogs with aggressive and phobic behavioral disorders. Heliyon. 2020 Jan 29;6(1):e03311. doi: 10.1016/j.heliyon.2020.e03311. PMID: 32021942. PMC: PMC6994854.

15. Tynes VV, Landsberg GM. Nutritional Management of Behavior and Brain Disorders in Dogs and Cats. Vet Clin North Am Small Anim Pract. 2021 May;51(3):711-727. doi: 10.1016/j.cvsm.2021.01.011. PMID: 33653540.

Editorial Information

Field	Detail
Published	December 2025
Last Updated	May 2026
Reviewed by	Veterinary Advisory Board
Next Review	April 2027
Author	Glendon Lloyd, Dip. Canine Nutrition (Dist.), Dip. Dog Nutrigenomics (Dist.), Founder, Bonza
Disclaimer	This article is for informational purposes only and does not constitute veterinary advice. Always consult a qualified veterinarian before making changes to your dog’s diet or supplement regimen.