When we think about what shapes our dogs’ behaviour, we usually focus on the obvious factors. Genetics, early socialisation, daily routines and the way we interact with them all play a big part. However, one factor often gets overlooked: what’s in the food bowl. So, does diet affect dog behaviour? A growing body of research suggests that it can, from anxiety and reactivity to impulse control and cognitive function.
As clinical animal behaviourists and veterinary behaviourists, we regularly consider nutrition as part of a holistic behaviour assessment. This isn’t about miracle cures or fad diets. Instead, it’s about understanding how what your dog eats can change how they feel and behave. It’s also about knowing when dietary changes might support a broader behaviour modification plan.
How Diet Affects Your Dog’s Brain and Behaviour
Your dog’s brain needs a steady supply of nutrients to make neurotransmitters. These are the chemical messengers that regulate mood, arousal and behaviour. When the balance of nutrients shifts, the effects on behaviour can be measurable. For example, this can happen through changes in diet composition, in nutrient availability, or in the way nutrients interact with each other.
A landmark review by Bosch and colleagues (2007) mapped out several ways that nutrition can influence canine behaviour. These include the supply of amino acids that the brain uses to build neurotransmitters, and the role of fatty acids in brain structure and function. The review also looked at how feeding patterns can affect frustration-related behaviour.
More recently, researchers have turned their attention to the gut-brain axis. This is the two-way communication system between the digestive tract and the brain. As a result, we now have entirely new ways to understand how diet affects dog behaviour.
Tryptophan, Serotonin and Behaviour
One of the best-studied links between diet and behaviour involves the amino acid tryptophan. Your dog’s body uses tryptophan to make serotonin, a neurotransmitter closely linked to mood, impulse control and emotional resilience. Researchers have linked low serotonin levels to anxiety, aggression and compulsive behaviours in both people and dogs.
In a small study of 33 dogs, DeNapoli and colleagues (2000) tested whether dietary protein and added tryptophan changed behaviour. When the researchers analysed all the dogs together, territorial aggression scores were lower on a low-protein diet with added tryptophan. Scores for aggression towards familiar people were highest on a high-protein diet without added tryptophan. (The study called this “dominance aggression”, a label behaviourists no longer use.)
So, in some contexts, a high-protein diet without enough tryptophan may make certain types of aggression worse. That said, this was a short study with a small number of dogs. Later research on tryptophan for anxious dogs has also produced mixed results.
It’s also worth knowing that tryptophan competes with other amino acids to cross from the blood into the brain. Because of this, simply adding more protein won’t necessarily raise brain serotonin. In fact, a very high-protein diet may reduce tryptophan uptake, because more amino acids are competing for the same route. In other words, the ratio of tryptophan to other amino acids matters more than the total amount.
Fatty Acids and Brain Health
Omega-3 fatty acids, particularly DHA (docosahexaenoic acid), play a key role in brain development and day-to-day brain function. DHA is a major building block of nerve cell membranes. Its availability can also influence the dopamine and serotonin systems, which are central to mood, learning and behaviour.
The balance between omega-3 and omega-6 fatty acids also seems to matter. Most commercial dog foods provide plenty of omega-6, but omega-3 levels can vary widely. Foods enriched with marine omega-3s, such as fish oil, may support cognitive function and emotional regulation. This may be especially relevant for growing puppies and older dogs.
The Gut-Brain Axis: Where Diet and Dog Behaviour Meet
Perhaps the most exciting area of recent research is the canine gut-brain axis. Your dog’s gut is home to trillions of microorganisms, known as the gut microbiota. These microbes communicate with the brain through metabolic, nerve, hormone and immune pathways. When this community falls out of balance (known as dysbiosis), it may contribute to behavioural and emotional problems.
A 2024 review by Sacoor and colleagues highlighted the central role of the gut microbiota in the gut-brain axis. The authors also suggested that dysbiosis may contribute to anxiety disorders in dogs, although research in dogs is still at an early stage.
Similarly, Pellowe and colleagues (2025) found that gut microbiota composition was linked to anxiety and aggression scores in pet dogs. In particular, one group of bacteria, Blautia, was consistently linked to higher anxiety scores.
Finally, a randomised controlled study by Sechi and colleagues (2017) followed 69 dogs with anxiety- and stress-related behaviour problems. Dogs fed a specific nutraceutical diet for 45 days showed higher serotonin and dopamine levels, and lower cortisol and oxidative stress markers. This is a single study of one commercial diet, so more research is needed. Even so, it offers encouraging evidence that a targeted diet can produce measurable changes in brain chemistry.
How to Support Your Dog’s Behaviour Through Diet
Once you know that diet can affect your dog’s behaviour, it’s tempting to overhaul their food straight away. However, it’s best to make changes thoughtfully and, ideally, with professional guidance. Here are some practical points to consider.
Start with a complete, balanced diet
Quality matters more than brand. The foundation is a complete and balanced diet from a reputable manufacturer that meets FEDIAF (or AAFCO) guidelines. From there, your vet or a veterinary nutritionist can help you decide whether any changes might benefit your dog.
Look at the whole picture
Diet is only one piece of the puzzle. A dog showing anxiety or reactivity needs a full behavioural assessment. This should consider their history, environment, relationships, physical health and emotional state. Dietary changes work best as part of a wider plan, rather than as a stand-alone fix.
Be cautious with supplements
Tryptophan, omega-3 fatty acids, probiotics and other nutraceuticals are now widely available. Even so, only use them under veterinary guidance. Dose, timing and interactions with other medication all matter. Also, a supplement that helps one dog may not suit another.
Think about how you feed, not just what
Feeding routines matter too. Research suggests that persistent hunger or frustration between meals can increase repetitive behaviours and aggression, and reduce resting time. Diets higher in fibre may help dogs feel fuller for longer. In addition, the way you feed can shape your dog’s overall state through the day. For example, you could look at meal frequency, food puzzle toys or scatter feeding.
Food Allergies and Intolerances: Another Way Diet Affects Dog Behaviour
Food allergies and intolerances get less attention in conversations about behaviour. However, they can change how your dog feels and, as a result, how they behave. A dog with ongoing tummy upsets, itchy skin or general inflammation may become more irritable and less tolerant of handling. They may also sleep less well and react more quickly to things that worry them.
Discomfort is a common, and often overlooked, driver of behaviour change. You can read more in our guide to the behavioural signs of pain. If your dog has unexplained behaviour changes alongside digestive or skin problems, speak to your vet. A dietary elimination trial under veterinary supervision may well be worth considering.
Need Support With Your Dog’s Behaviour?
At Second Nature Behaviour, we take a whole-dog approach to behaviour assessment. That means we consider everything from your dog’s diet and physical health to their emotional state and environment. Our clinical animal behaviourists and veterinary behaviourists work closely with your vet, so that every part of your dog’s wellbeing is addressed, including nutrition.
If you’re worried that diet might affect your dog’s behaviour, the first step is always to speak to your vet. Once your vet has checked for any medical causes, they can refer you to us for a full behaviour consultation.
Get in touch to find out more →
References and Further Reading
- Bosch, G., Beerda, B., Hendriks, W.H., van der Poel, A.F.B. & Verstegen, M.W.A. (2007). Impact of nutrition on canine behaviour: current status and possible mechanisms. Nutrition Research Reviews, 20, 180–194.
- DeNapoli, J.S., Dodman, N.H., Shuster, L., Rand, W.M. & Gross, K.L. (2000). Effect of dietary protein content and tryptophan supplementation on dominance aggression, territorial aggression, and hyperactivity in dogs. Journal of the American Veterinary Medical Association, 217(4), 504–508. https://doi.org/10.2460/javma.2000.217.504
- Pellowe, S.D., Zhang, A., Bignell, D.R.D., Peña-Castillo, L. et al. (2025). Gut microbiota composition is related to anxiety and aggression scores in companion dogs. Scientific Reports, 15.
- Sacoor, C., Marugg, J.D., Lima, N.R., Empadinhas, N. & Montezinho, L. (2024). Gut-brain axis impact on canine anxiety disorders: new challenges for behavioral veterinary medicine. Veterinary Medicine International, 2024, 2856759. https://doi.org/10.1155/2024/2856759
- Sechi, S., Di Cerbo, A., Canello, S., Guidetti, G., Chiavolelli, F., Fiore, F. & Cocco, R. (2017). Effects in dogs with behavioural disorders of a commercial nutraceutical diet on stress and neuroendocrine parameters. Veterinary Record, 180(1), 18. https://pmc.ncbi.nlm.nih.gov/articles/PMC5284471/
- Tynes, V.V. & Landsberg, G.M. (2021). Nutritional management of behavior and brain disorders in dogs and cats. Veterinary Clinics of North America: Small Animal Practice, 51(3), 711–727.