How Your Dog’s Gut Microbiome Affects His Behavior

By Katie B. Kangas, DVM, CVA, CVCP

Canine behavioral problems like anxiety and aggression can have many causes, and an out-of-balance microbiome may be one of them. Learn how your dog’s gut health can influence his behavior. 

If you’ve been learning about your dog’s (or your own) microbiome, you may be familiar with the term “gut-brain axis”. Several years ago, medical scientists suggested the gut was the “second brain” because so many of the neurotransmitters used by the brain and nervous system are created in the gut. However, the latest research suggests the enteric system (gut) may actually be viewed as the first or primary brain. That’s because gut health and microbes influence mental condition and behaviors such as aggression and anxiety (as well as immune function and overall health) in both humans and animals. Let’s take a look at how your dog’s gut health can impact his behavior.

Bacteria in the gut communicate with the brain

Gut bacteria make chemicals that communicate with the brain through the nerves and hormones — this connection is called the gut-brain axis. In fact, it is now known that many key chemicals and hormones used by the brain and nervous system, such as serotonin, dopamine and GABA, are produced in the gut.

  • Serotonin impacts mood and anxiety, and has actually been termed the “happy chemical” because it contributes to emotional well-being, while low levels of serotonin have been associated with depression. It is estimated that 70% of serotonin is made in the gut.
  • Dopamine is involved in motor function, mood, decision-making, and the control of other hormones. Reports estimate that about 50% of dopamine is produced in the gastrointestinal tract by enteric neurons and intestinal cells.
  • GABA – Gamma Aminobutyric acid regulates stress, anxiety and sleep patterns, and is known to be modulated by bacteria in the gut microbiome.

To be clear, “microbiome” is the term used to describe the vast ecosystem of bacteria, fungi and viral organisms that live within the bodies of all other living organisms, including you and your dog. Our microbe populations actually far exceed the number of our cells. In fact, the number of microbial organisms living in just the intestinal environment is ten times greater than the number of cells in the host’s body! Everybody’s microbiome is essentially like a fingerprint, unique to the individual, but animals within the same species will have many similarities. The more diverse the microbiome is, the healthier the person or animal will be!