How Nutrition Influences Behavior
Written by Kristine Strøm (PoteNord), this article highlights how a dog’s physical state, especially nutrition and gut health, can shape behavior, stress tolerance, and the ability to learn.
Introduction
When we aim to change behavior, it is natural to first think about training methods: setup, reinforcement, distance, repetitions, and criteria. These are important tools, but how successful we are in training is also influenced by the state of the body. If the body and mind must use energy to cope with burdens such as itching, allergies, and/or gastrointestinal imbalance, the dog’s capacity may be reduced. The tolerance window becomes narrower, and the dog may more easily go over threshold. The result can be that the dog is triggered more quickly, becomes more restless or frustrated, and that learned behaviors “slip” more easily in challenging situations. This does not necessarily mean that the dog cannot, but rather that, in that moment, the dog is not able to access the skill.
Why Is This Relevant in Behavior Modification?
Whether the challenge involves restlessness, handling issues, resource guarding, separation-related problems, reactivity, or other difficulties, it is rarely sufficient to simply try to “stop” the behavior we consider problematic. For lasting change, we must change what the dog feels, expects, and chooses in a situation. To achieve this, the dog must actually have the capacity to learn and self-regulate. For learning to occur, the dog needs: - to remain within a manageable level of stress (below threshold) - to be able to receive reinforcement/reward (food, toys, social or environmental reinforcers) - to have sufficient recovery between sessions (quality sleep and rest) When the body is out of balance, the dog may become more reactive, more restless, more easily frustrated—and have a “shorter fuse.” Not because the dog is difficult, but because capacity is limited.
When the Body Interferes with Learning: Why We Often Need to Stabilize First
In some cases, training-based interventions alone can be effective. In other cases, however, the physical burden is so significant that it becomes difficult to achieve lasting progress before the dog’s physical state improves. Discomfort must be reduced, and sleep and rest must improve before clear training progress can be expected. Research on itching/atopic dermatitis shows associations between chronic itch and increased prevalence of fear, anxiety, and aggression in some dogs. When a dog experiences persistent itching, it is therefore plausible that this can make it more difficult for training to “stick.” In many cases, it is therefore necessary to work along two parallel tracks: 1) Reduce physical burden (e.g., itching, gastrointestinal issues, discomfort—often with veterinary support, ideally in collaboration with a nutritionist. 2) Implement temporary adjustments in training and daily life that promote safety and success, and prevent unwanted behaviors from becoming more strongly established.
Gut and Brain: The Gut–Brain Axis
In addition to the impact of itching, gastrointestinal issues, and other discomfort on capacity and tolerance, there is increasing evidence of bidirectional communication between the gut and the brain—known as the gut–brain axis. The gut and brain communicate through several systems, including: - the nervous system (e.g., the vagus nerve) - the immune system (inflammatory signaling) - the hormonal/stress system (HPA axis, cortisol) - microbial metabolites (e.g., short-chain fatty acids/SCFAs) In dogs, this is a growing field of research. Evidence suggests that this gut–brain communication may be relevant in anxiety and stress, but more research is needed before we can determine exactly how this applies to individual dogs. Recent studies also indicate that the composition of the gut microbiome may be associated with behavioral traits such as anxiety and aggression. This supports the idea that the gastrointestinal system can be an important part of the overall picture. Importantly, this relationship is bidirectional: stress can also influence the dog’s gut microbiome.
In Summary
The gut and brain influence each other. We also know that both internal and external factors affect behavior. When working with dog training—especially behavior modification—it is therefore useful to consider the body as part of the equation. Not necessarily as a simple explanation, but as a factor that can influence threshold, sleep, and overall capacity. This is general information and does not replace veterinary assessment. In cases of persistent gastrointestinal issues, severe itching/pain, ear problems, blood in stool, or rapid changes in general condition, a veterinarian should be consulted.
References
McAuliffe, L.R. et al. (2022). Associations Between Atopic Dermatitis and Anxiety, Aggression, and Fear-Based Behaviors in Dogs. Journal of the American Animal Hospital Association. Sacoor, C. et al. (2024). Gut-Brain Axis Impact on Canine Anxiety Disorders: New Challenges for Behavioral Veterinary Medicine. Veterinary Medicine International. Crisante, A. et al. (2025). A critical review of research concerning the gut microbiome in dogs and its relationship with behaviour. Applied Animal Behaviour Science. Pellowe, S.D. et al. (2025). Gut microbiota composition is related to anxiety and aggression scores in companion dogs. Scientific Reports. Patel, K.V. et al. (2024). Impact of acute stress on the canine gut microbiota. Scientific Reports.