The gut-brain connection

In this video interview with dvm360 during the 2026 Fetch Charlotte conference, Callie Harris, DVM, broke down the emerging science of psychobiotics, which are probiotics that may benefit mental health by tapping into the gut-brain axis. From reduced cortisol to increased serotonin, the research suggests that what's happening in your pet's gut may have a greater influence on their mood than veterinary professionals would expect.

Below is a full transcript, edited lightly for clarity.

dvm360: Starting with your name, can you tell us a little bit about yourself?

Callie Harris, DVM: I'm Dr Callie Harris. I'm a small-animal veterinarian and a Purina veterinarian. I'm based in Atlanta, [Georgia]. My clinical background is emergency medicine, and I made that transition into industry almost a decade ago. I still practice on the side every other weekend, and I wear a lot of different hats as a veterinarian for Purina.

dvm360: The concept of psychobiotics was introduced in 2013. Based on the mouse model studies mentioned, how does the gut microbiota actually influence a pet's behavioral disposition?

Harris: There's been some really interesting data that [have] come out, particularly on the [mouse] models, [and] on humans, too. When we refer to a psychobiotic…from a definition standpoint, this is just a probiotic that is expected to confer benefit from a mental health standpoint with our patients, right? So there's been a lot of information [coming] out that showcases that there's something called the gut-brain axis, or that gut-brain connection. So how we interact with the microbiota, or what's taking place in our patients, or even our own gut, can now send up signaling to the brain. The brain can receive it and then send signaling back to the gut, so it's a bidirectional pathway of communication between the 2.

Now there's been some conversation around the specific mechanism of action, and I have to admit that it hasn't been completely teased out. There have been thoughts [that] maybe there are neurotransmitters being released. At least in the studies that have been done on probiotics within the Purina portfolio that we use for pets with anxiety, we understand that cortisol, that stress hormone, actually goes down [and] serotonin goes up.

So again, there's just been a lot of exchange of information that really strongly demonstrates that, again, there's that gut-brain connection. But there are a ton of studies now that you can find more information on, particularly on Purina Institute.

Want to learn more for Harris? She will be presenting at Fetch Encore on May 17, 2026! Join Harris and other veterinary nutrition experts for a day full of learning, and you can earn up to 6 continuing education credits. Learn more and register here today for just $25!