How Gut Health Shapes Cognition, Behaviour, and Emotional Wellbeing
“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
A dog’s gut microbiome directly influences mood, stress resilience, and cognitive function, with over 90% of serotonin produced in the gut, gut dysbiosis is a clinically recognised root cause of anxiety, behavioural disorders, and cognitive decline in dogs.
This sophisticated signalling system influences virtually every aspect of canine mental health, from moment-to-moment mood and stress responses to long-term cognitive function and behavioural patterns.1,7,8 This guide examines the science of gut-brain communication and provides evidence-based nutritional strategies for supporting canine mental and emotional wellbeing.
At Bonza, the gut-brain axis is one of the eight gut-organ axes underpinning the “One Gut. Whole Dog.” philosophy, addressed through the Biotics Triad of prebiotics, probiotics, and postbiotics in the Bioactive Bites range of functional supplements, with Bliss formulated specifically to support gut-brain axis function through ashwagandha, L-tryptophan, and Calsporin®.
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:
- Summary
- Key Takeaways
- Introduction
- Understanding the Gut-Brain Axis
- The Gut-Brain Axis and Canine Anxiety Disorders
- Neurodegenerative Diseases and the Gut-Brain Connection
- Canine Behavioural Disorders and Gut Health
- Nutritional Modulation of the Gut-Brain Axis
- Supporting Your Dog’s Gut-Brain Axis: The Bonza Approach
- How to Support Your Dog’s Gut-Brain Axis Through Nutrition
- Frequently Asked Questions
- Conclusion
- References
Introduction
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.
Understanding the Gut-Brain Axis
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.
The Enteric Nervous System: The Second Brain
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
Communication Pathways Between Gut and Brain
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
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
Neurotransmitter Production in the Gut
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 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
The Role of the Microbiome in Brain Function
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
The Gut-Brain Axis and Canine Anxiety Disorders
Anxiety disorders represent one of the most common behavioural problems in dogs, causing significant distress for both pets and their owners.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
Types of Anxiety in Dogs
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 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
The Stress-Gut-Brain Feedback Loop
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
Nutritional Strategies for Anxiety Support
Dietary intervention can support anxious dogs through multiple gut-brain axis mechanisms:1,8
Tryptophan supplementation: As the dietary precursor to serotonin, adequate tryptophan intake is essential for mood regulation. Studies demonstrate that tryptophan supplementation can reduce anxiety behaviours and improve stress tolerance in dogs.1,8
Psychobiotic probiotics: Specific probiotic strains, particularly Lactobacillus and Bifidobacterium species, have demonstrated anxiety-reducing effects.1,8 Lactobacillus helveticus is particularly well-researched for its mood-modulating properties through gut-brain axis mechanisms.1
GABA-supporting nutrients: Magnesium supports GABA receptor function and has natural calming effects. B vitamins, particularly B6, are essential cofactors for neurotransmitter synthesis.1
Anti-inflammatory omega-3s: DHA and EPA reduce neuroinflammation that may contribute to anxiety.3 They also support healthy brain cell membranes and neurotransmitter receptor function.3
Calming botanicals: Herbs including passionflower, lemon balm, and chamomile have demonstrated calming effects, often through GABA-modulating mechanisms.8 Adaptogens like ashwagandha help regulate the HPA axis and reduce cortisol.1
Neurodegenerative Diseases and the Gut-Brain Connection
As dogs age, many experience cognitive decline that parallels human dementia.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
Canine Cognitive Dysfunction Syndrome
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 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
Neuroinflammation and Microbiome Alterations
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
Oxidative Stress and Cognitive Decline
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
Neuroprotective Nutritional Approaches
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
Canine Behavioural Disorders and Gut Health
Beyond anxiety, various behavioural disorders in dogs show connections to gut health and may be influenced by gut-brain axis dysfunction.2,8 Understanding these connections opens additional avenues for supporting dogs with challenging behaviours.
Aggression and Impulse Control
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 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
Compulsive Behaviours
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
Hyperactivity and Attention Difficulties
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
Dietary Influences on Behaviour
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
Nutritional Modulation of the 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
Prebiotics for Brain Health
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
Psychobiotics: Probiotics for Mental Health
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.
Postbiotics and Metabolite Delivery
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
Essential Nutrients for Neurotransmitter Synthesis
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
Omega-3 Fatty Acids and Brain Function
DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) support brain health through multiple mechanisms.3 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.
Adaptogenic Herbs and Calming Botanicals
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.
Supporting Your Dog’s Gut-Brain Axis: The Bonza Approach
Bonza’s “One Gut. Whole Dog.” philosophy recognises that mental and emotional wellbeing begins in the gut. 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
Applying gut-brain axis science to support your dog’s mental and emotional health involves several practical considerations:
- Choose a diet with gut-brain supporting ingredients.
Select a complete food that includes named probiotic strains, prebiotic fibres, omega-3 DHA from identified sources, and supportive nutrients for neurotransmitter synthesis such as tryptophan, B vitamins, and magnesium.6 The quality of functional ingredients matters more than quantity – look for named strains, standardised extracts, and bioavailable mineral forms rather than generic label claims.
Bonza Superfoods & Ancient Grains is formulated to meet this specification, combining Calsporin®, TruPet™ postbiotic, dried chicory as prebiotic, DHAgold® algae-derived omega-3, and PhytoPlus® adaptogenic botanicals within a single complete food built around the gut-brain axis as a primary formulation objective. - Address specific concerns with targeted supplementation.
For dogs with anxiety, cognitive decline, or challenging behaviours, a supportive base diet alone may not deliver therapeutic levels of key compounds.1,8 Calming supplements for dogs providing concentrated psychobiotics, tryptophan, calming botanicals, and adaptogens can complement the daily diet by targeting multiple gut-brain axis pathways simultaneously.1,8
- Build and maintain a diverse gut microbiome.
Support beneficial bacterial populations through a combination of prebiotic and probiotic ingredients.6 Prebiotic fibres from sources like chicory root and inulin selectively nourish SCFA-producing bacteria, whilst probiotics and postbiotics deliver direct gut-brain benefits.6 Dietary variety in plant-based fibres further promotes microbial diversity associated with resilient gut health.6
- Protect the gut during stressful periods.
Anticipated stressors such as moving house, family changes, fireworks season, kennel stays, or veterinary visits warrant proactive gut support to prevent stress-induced dysbiosis and its cascading effects on mood and behaviour.1,8 Begin supplementation several days before known stressful events and continue afterwards, as cortisol-driven gut disruption can persist long after the stressor has passed.1
- Combine nutritional support with appropriate behavioural management.
Gut-brain axis nutrition works best as part of a comprehensive approach alongside appropriate behavioural training, environmental modification, and, where indicated, veterinary treatment.2 Nutritional strategies can make behavioural interventions more effective by improving the neurochemical environment underlying learning, emotional regulation, and stress resilience – issues.1,2
- Start brain-supporting nutrition early for cognitive health.
Supporting gut-brain axis function proactively throughout life is more effective than trying to reverse established cognitive decline.3,4 Introduce DHA omega-3, antioxidants, B vitamins, and microbiome-supporting ingredients in middle age rather than waiting for signs of impairment.3,4 Neuroprotective nutrition is most beneficial before significant neuronal damage has occurred.3
- Allow adequate time for gut-brain changes to develop.
Microbiome shifts and their downstream effects on neurotransmitter production, inflammation, and brain signalling develop gradually.6 Allow four to eight weeks of consistent dietary intervention before evaluating response for anxiety or behavioural concerns.6 Cognitive support in senior dogs may take longer still.3 Premature discontinuation is a common reason for apparent supplement failure – patience is essential.
- Monitor your dog’s response and adjust accordingly.
Every dog’s microbiome and neurological makeup is unique, and responses to gut-brain axis nutrition will vary.6 Track changes in anxiety behaviours, sleep quality, digestive comfort, energy levels, and cognitive function over time. Be prepared to adjust supplement choices, dosages, or dietary composition if initial results are disappointing – the optimal combination differs between individuals.
Frequently Asked Questions
The gut-brain axis is the bidirectional communication network connecting your dog’s gastrointestinal tract to their brain. It operates through neural pathways (primarily the vagus nerve), hormonal signals, immune system messengers, and metabolites produced by gut bacteria. This axis matters because it means gut health directly influences brain function, affecting mood, anxiety levels, cognitive ability, and behaviour. Problems in the gut can manifest as mental health issues, whilst stress can disrupt gut function, creating feedback loops that maintain both physical and psychological symptoms. Understanding this connection reveals why nutritional strategies targeting gut health can support your dog’s mental and emotional wellbeing.
Yes, substantial research supports this connection. Dogs with anxiety disorders consistently show altered gut microbiome compositions, with reduced populations of beneficial bacteria that produce calming compounds. The gut produces the majority of the body’s serotonin and influences GABA availability, both neurotransmitters central to calm and emotional regulation. Gut inflammation can send distress signals to the brain via immune pathways and the vagus nerve. Studies demonstrate that specific probiotic strains can reduce anxiety behaviours in dogs, and dietary interventions supporting gut health can improve stress resilience. Whilst gut health support should complement rather than replace appropriate behavioural management, it offers a valuable additional tool for helping anxious dogs.
Gut bacteria influence the brain through multiple mechanisms. They produce neurotransmitters directly, including GABA and dopamine, and regulate the synthesis of serotonin by gut cells. They generate metabolites like short-chain fatty acids that cross the blood-brain barrier and affect brain inflammation and function. They modulate immune signalling that reaches the brain. They influence vagus nerve activity, which transmits information about gut conditions directly to brain regions controlling mood and stress. They affect the hypothalamic-pituitary-adrenal axis governing cortisol release. Different bacterial species have different effects, making microbiome composition a significant determinant of brain function and mental health.
Psychobiotics are specific probiotic strains that confer mental health benefits when consumed. Unlike general probiotics that primarily support digestive health, psychobiotics have demonstrated effects on mood, anxiety, stress response, or cognitive function through gut-brain axis mechanisms. Lactobacillus helveticus is among the most studied, showing ability to reduce anxiety behaviours and cortisol levels. Other psychobiotic strains include certain Lactobacillus rhamnosus and Bifidobacterium species. These beneficial bacteria can help anxious dogs by producing calming neurotransmitters, reducing inflammatory signals to the brain, improving stress resilience, and supporting healthy gut-brain communication. They work gradually over several weeks of consistent supplementation.
Research supports the role of nutrition in maintaining cognitive function during ageing. DHA omega-3 fatty acids support brain cell membrane integrity and have demonstrated ability to improve cognitive measures in senior dogs. Antioxidants help combat the oxidative stress that contributes to brain ageing. B vitamins support neurological function and neurotransmitter synthesis. Supporting gut microbiome health reduces neuroinflammation associated with cognitive decline. Medium-chain triglycerides may provide alternative brain fuel. Whilst no nutritional intervention can completely prevent age-related cognitive changes, a comprehensive brain-supporting diet can help maintain function longer and potentially slow decline. Starting proactively before significant impairment develops is more effective than trying to reverse established changes.
Tryptophan is an essential amino acid that serves as the sole dietary precursor for serotonin, the neurotransmitter most associated with calm mood, emotional stability, and impulse control. Dogs cannot synthesise tryptophan and must obtain it from food. Once absorbed, tryptophan can cross the blood-brain barrier where it is converted to serotonin through a process requiring adequate B vitamins. Low serotonin is associated with increased anxiety, aggression, and impulsivity. Studies demonstrate that tryptophan supplementation can reduce anxiety behaviours, decrease territorial aggression, and improve stress tolerance in dogs. Gut bacteria also influence tryptophan availability, some compete for it whilst others facilitate its conversion to serotonin.
Adaptogens are herbs that help the body adapt to stress by regulating the hypothalamic-pituitary-adrenal (HPA) axis, the hormonal system controlling cortisol release. Ashwagandha (Withania somnifera) is among the most researched, containing compounds called withanolides that modulate stress hormone production. Rather than sedating, adaptogens help normalise stress responses, reducing excessive cortisol whilst supporting appropriate alertness. This makes them valuable for dogs with chronic anxiety or heightened stress sensitivity. Ashwagandha has demonstrated anxiolytic effects in studies, reducing stress behaviours without causing drowsiness or personality changes. It works synergistically with gut-brain axis support by addressing the hormonal component of stress whilst probiotics and prebiotics address the microbial component.
Serotonin plays a crucial role in impulse control and the regulation of aggressive behaviour. Low brain serotonin is consistently associated with increased aggression across species. Since gut bacteria significantly influence tryptophan availability (serotonin’s precursor) and serotonin metabolism, gut dysbiosis can contribute to impaired impulse control. Gut inflammation also sends signals that may promote irritability and reactive behaviour. Research shows that dietary tryptophan supplementation can reduce territorial aggression in dogs, supporting the gut-behaviour connection. Whilst aggression has many potential causes requiring professional assessment, supporting gut health and serotonin production through nutrition may be a helpful component of a comprehensive management approach.
Microbiome changes and their downstream effects on brain function develop gradually rather than overnight. Some dogs show subtle improvements in digestive comfort within the first week or two. Behavioural changes typically require longer, most recommendations suggest allowing four to eight weeks of consistent supplementation before evaluating response to dietary interventions for anxiety or behaviour. Cognitive support in senior dogs may take even longer to show observable effects. Some acute situational supplements containing calming botanicals like passionflower can produce more immediate effects within 30-60 minutes, but the foundational gut-brain axis changes require patience. Premature discontinuation is a common reason for apparent supplement failure.
Nutritional support should complement rather than automatically replace pharmaceutical treatment for dogs with significant anxiety. For mild anxiety or as part of a preventive approach, gut-brain supporting nutrition may provide sufficient support. For moderate to severe anxiety, combining nutritional strategies with appropriate medication often produces better outcomes than either approach alone. Never discontinue prescribed medications without veterinary guidance. That said, some dogs initially requiring medication may be able to reduce doses or transition to nutritional support alone as their gut-brain axis function improves, always under veterinary supervision. The goal is optimal wellbeing for your dog using whatever combination of tools proves most effective.
Magnesium plays essential roles in nervous system function. It supports GABA receptor activity, GABA being the primary calming neurotransmitter. Magnesium helps regulate the stress response by modulating HPA axis activity. It supports energy production in neurons and is required for numerous enzymatic reactions in neurotransmitter synthesis. Chronic stress depletes magnesium stores, potentially creating a cycle where stress-induced deficiency increases stress sensitivity. The form of magnesium matters: magnesium glycinate offers excellent bioavailability and the amino acid glycine provides additional calming benefits. Adequate magnesium intake supports relaxation, stress resilience, and balanced nervous system function.
Stress and gut health exist in a bidirectional relationship that can create vicious cycles. When your dog experiences stress, cortisol release and sympathetic nervous system activation reduce blood flow to the gut, alter motility (causing either diarrhoea or constipation), increase intestinal permeability (‘leaky gut’), and create conditions unfavourable to beneficial bacteria. This stress-induced gut disruption then signals back to the brain through inflammatory pathways, vagal nerve transmission, and altered neurotransmitter production, potentially increasing anxiety and stress sensitivity. Breaking this cycle requires addressing both components, managing environmental stressors whilst simultaneously supporting gut health to reduce the gut-derived signals maintaining the stressed state.
Effective calming supplements for dogs should address multiple gut-brain axis pathways rather than relying on a single ingredient. Look for psychobiotic probiotic strains (particularly Lactobacillus helveticus), tryptophan for serotonin support, magnesium for GABA receptor function, B vitamins for neurotransmitter synthesis, calming botanicals like passionflower and lemon balm, adaptogens like ashwagandha for HPA axis regulation, and omega-3s for brain health and anti-inflammatory effects. The combination matters, ingredients work synergistically when addressing complementary pathways. Also consider postbiotic ingredients that deliver benefits reliably regardless of individual microbiome variability. Quality manufacturing and appropriate dosing for your dog’s size are also important factors.
Yes, the gut-brain axis influences sleep through several mechanisms. Melatonin, the hormone regulating sleep-wake cycles, is synthesised from serotonin, and serotonin production depends heavily on gut-derived tryptophan and healthy microbiome function. Gut inflammation can disrupt sleep through inflammatory signals reaching the brain. Cortisol dysregulation associated with gut dysbiosis affects circadian rhythms. Some gut bacteria directly influence circadian gene expression. Dogs with disrupted sleep patterns, including those with Canine Cognitive Dysfunction showing reversed sleep-wake cycles, may benefit from gut-brain axis support. Adequate tryptophan intake, probiotics supporting serotonin metabolism, and magnesium for relaxation can all contribute to healthier sleep patterns.
Gut-brain supporting supplements using natural ingredients are generally well-tolerated, though individual responses vary. Probiotic introduction may occasionally cause temporary digestive adjustment as the microbiome shifts, typically resolving within a few days. High doses of certain ingredients could cause soft stools. Some calming botanicals may cause mild drowsiness in sensitive individuals, though this is usually considered a feature rather than a side effect. Quality supplements use ingredients with established safety profiles at appropriate doses. However, always inform your veterinarian about supplements your dog receives, particularly if they have underlying health conditions or take medications. Interactions are uncommon but possible with certain drugs.
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.
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.
Editorial Information
| Last reviewed | March 2026 |
| Next review due | March 2027 |
| Author | Glendon Lloyd, Dip. Canine Nutrition (Dist.), Dip. Canine Nutrigenomics (Dist.) |
| Medical 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. |
