Gut Feelings | Anxiety and the Microbiome
Anxiety and Aggression in Dogs: How Diet and the Gut Microbiome Play a Role
If your dog struggles with anxiety or shows aggressive behaviours, you’re not alone. These are common behaviour issues that can be stressful for both dogs and their families. Recent research suggests the gut microbiome, the community of bacteria living in the intestines, may play a surprising role. These microbes communicate with the brain through the gut–brain axis, influencing mood, stress, and behaviour. This means what your dog eats could directly affect how they feel and behave.
Why Look at the Gut?
The gut and brain are linked through the vagus nerve, the immune system, stress hormones, and chemicals made by gut microbes. For example, short-chain fatty acids (SCFAs), produced when bacteria ferment dietary fibres, help reduce inflammation and support brain health. The amino acid tryptophan, found in protein foods, is converted into serotonin (the 'feel-good' chemical) with the help of microbes. All of this means the gut microbiome may directly influence how anxious or calm your dog feels.
What Do Studies Show?
Several studies have found differences in gut bacteria between dogs with anxiety or aggression and those without. For example, some studies found more of certain bacteria like Blautia in anxious dogs, while fearful dogs had more Lactobacillus. Although the science is still developing, these findings suggest the microbiome could be linked to behaviour.
Prevotella, Diet, and New Approaches
Recent studies have noted that dogs with high drive or strong motivation traits may show an increase in Prevotella in their gut. Prevotella is linked with carbohydrate fermentation and while not always harmful, overgrowth can disrupt balance. One interesting area of research is the use of fucoidan. A natural compound from seaweed which shows antimicrobial effects that may help regulate Prevotella levels. Another developing tool is faecal microbiota transplantation (FMT), which involves repopulating the gut with a healthy donor microbiome. While still experimental in dogs, FMT has the potential to restore microbial balance where severe dysbiosis is present
How Diet Shapes the Microbiome
Diet is one of the strongest influences on the microbiome. What your dog eats feeds their microbes, which in turn influence behaviour:
Fibre-rich foods (pumpkin, oats, beet pulp, vegetables) increase SCFA-producing bacteria that calm inflammation.
Protein-rich diets (meat, fish, eggs) feed bacteria like Fusobacteria that help digest protein, but need balance with fibre.
High-fat, processed diets may increase Proteobacteria, linked with gut imbalance and inflammation.
Polyphenols in herbs (oregano, rosemary, thyme) and blueberries help support beneficial microbes and reduce harmful ones.
Mechanisms Linking Gut and Behaviour
SCFAs: Reduce gut and brain inflammation, influence mood.
Tryptophan: Microbes help regulate whether this amino acid becomes serotonin (calming) or kynurenine (linked to stress).
Vagal and immune pathways: Microbes send constant signals that tune how the brain responds to stress.
Can Changing the Gut Change Behaviour?
Some diet and supplement strategies show promise:
Probiotics: Specific strains like Bifidobacterium longum (BL999) reduced anxious behaviour in a trial, and Lactobacillus plantarum PS128 also shows potential.
Tryptophan: Adding tryptophan to the diet has reduced aggression in some dogs, though results are mixed.
Balanced diets: Moving from highly processed foods to diets rich in whole foods, fibre, and omega-3 fatty acids may improve gut and behaviour health over time.
What You Can Do Now
Even while research continues, there are safe, practical steps you can take to support your dog’s gut and behaviour:
Add fibre: Pumpkin, carrots, oats, or prebiotic supplements help beneficial bacteria thrive.
Include omega-3s: Fish oil reduces inflammation and supports the brain.
Rotate proteins and whole foods: Variety encourages a diverse microbiome.
Try targeted probiotics: Use strains with published benefits and allow 4–6 weeks to see results.
Keep routines stable: Regular feeding, sleep, and exercise schedules help both stress hormones and microbes stay balanced.
Conclusion
The gut microbiome is an exciting new area in canine behaviour research. While diet alone may not cure anxiety or aggression, supporting a healthy, balanced microbiome can make a meaningful difference. A diverse diet with fibre, quality protein, and anti-inflammatory nutrients, when combined with training, veterinary care, and love, offers the best support for your dog’s wellbeing.
Dr. Carol Hughes
Biome 4 Pets
If you’re interested in discovering your dog’s unique microbiome configuration, use my code AUGUSTUS for 20% off all test kits.
I choose to work with this company because I feel that they genuinely care for our pets. I met Dr Carol at a conference and told her about the plight of breeds with gluten intolerance, how under and misdiagnosed it is. As a terrier mum herself, she not only listened, she hand made contamination free products to help our dogs. She hand selected new suppliers to make sure no rosemary or gluten products were grown, harvested or processed alongside the others.
Her passion is contagious, her depth of knowledge is unrivalled, her compassion, just like mine is dedicated.
Thank you for learning about this with me at the bleeding edge of this exciting new science. And thank you for caring so much about dogs.
Lana
Soco Fairy Dog Mother
References (Selected)
· Pellowe SD, Zhang A, Peña-Castillo L, Walsh CJ. Gut microbiota composition is related to anxiety and aggression scores in companion dogs. Sci Rep. 2025;15:24336.
· Kirchoff NS, Udell MAR, Sharpton TJ. The gut microbiome correlates with conspecific aggression in rescued dogs. PeerJ. 2019;7:e6103.
· Mondo E, Barone M, Soverini M, et al. Gut microbiome structure and adrenocortical activity in dogs with behavioural disorders. Heliyon. 2020;6(1):e03311.
· Sacoor C, Marugg JD, Lima NR, Empadinhas N, Montezinho L. Gut–Brain Axis Impact on Canine Anxiety Disorders. Vet Med Int. 2024;2856759.
· DeNapoli JS, Dodman NH, Shuster L, Rand WM, Gross KL. Effect of dietary protein and tryptophan supplementation on aggression in dogs. JAVMA. 2000;217:504-508.
· Templeman JR, Cant JP, Osborne VR, Shoveller AK. The effect of dietary tryptophan on canine behaviour. Can Vet J. 2018;59:891-897.
