The Latest on Dog Gut Health and Behavior: What We Know and Don’t Know

Researchers are taking a closer look at canine gut health.  image: AdobeStock

Gut health has become a hot topic in both human and veterinary medicine, and many pet owners are curious about how it may influence their dogs' behavior. I recently sat down with Dr. Sophie Liu, a veterinary behaviorist, to discuss this emerging field and how diet and gut health could be affecting our dogs. 

Sara: Thank you for joining me today, Dr. Liu. Let’s start by getting to know you a little better. Can you tell us about your background and how you became interested in dog behavior?

Dr. Liu: I’ve always had an interest in animal behavior, but it really developed into a passion after I got my first “heart dog,” a Doberman-German Shepherd mix who was dog-aggressive. By the time she turned two, she had bitten four dogs and narrowly missed being reported to authorities and likely euthanized. But she was also incredibly food-motivated, fun to train, and I fell in love with the art and science of excellent dog training. I began volunteering for the late Dr. Sophia Yin, pursued animal behavior opportunities during college at UC Berkeley, and continued pursuing behavior during vet school at Cornell University. After graduating from vet school, I entered a behavior medicine residency at San Francisco SPCA. I now share my home with two Dobermans, the youngest of which I bred and am pursuing bite sports with, a Taiwan rescue dog… and, of course, my patient husband.

Sara: It sounds as though your journey into dog behavior has been both personal and professional. Working with a dog-aggressive dog must have been challenging, but it also seems to have been a catalyst for your passion in this field. Now, as someone who is well-versed in dog behavior, can you share some of the common behavioral issues in dogs that might be linked to their diet or gut health?

Dr. Liu: Dogs can’t tell us how they feel. All we have to go on is careful observation and objective assessments. That’s why it’s so important to simply observe our dogs, without judgment, and let their actions and body language give us a better sense of what might be happening. Some common signs that we know are linked to potential gastrointestinal (GI) distress are lip licking, especially if the dog extends their neck and lip licks frequently, frequent burping, flatulence, licking of self (i.e., paws, abdomen, inguinal area), a kyphotic posture (rounding their back), or a “prayer” position (staying in a downward dog posture). Because of this, we might see behavioral signs like reluctance to interact, increased irritability, which can lead to defensive behaviors, skin reactions, excessive scratching or licking, reduced food interest, and even guarding food.

Sara: It seems as if some of these behaviors could easily be overlooked or mistaken for other issues. Can you explain the role of the gut microbiome in a dog’s health and how it might affect their behaviors?

Dr. Liu: Well, the truth is, we don’t know a lot of specific details about the dog microbiome and its relationship to behavior, at least from a causal perspective. First, the microbiome refers to the population of microbiota that live within a particular physical and chemical environment, such as within your dog’s gut. In common conversation, this typically refers to the bacteria and yeast that live within your dog’s large intestine—where dietary matter is fermented and where the products of those processes help actually nourish the gut cells and play a role in chemical and endocrine signaling. The gut is actually heavily innervated, and there’s a ton of interesting evidence in people and other animals that the “gut-brain axis” has profound potential to influence how an organism thinks or feels, based on how the gut is nourished or not.

We have small lines of interesting evidence, and lots of potential ones, about the relationship between behavior and the gut microbiome. However, we don’t have a robust body of literature that specifically says “X” species causes decreased aggression or “Y” species causes anxiety. We do have some interesting correlational findings that will require more research to clarify. For example, we are starting to build a general picture of which bacterial phyla or genera tend to be common in “normal” healthy dogs, and there are some small studies that suggest certain bacterial populations may be more associated with aggressiveness or anxiety, but none of these are causative; they are entirely correlational at this stage, which means there could be a third alternative cause that creates both anxiety/aggression and altered microbiome. And there are a few studies and white papers that are starting to suggest that specific bacterial strains or mixtures, or prebiotics and probiotics, may be helpful in changing behavior positively. These findings have yet to be replicated, however.

Sara: So while there’s a lot of potential, there’s still much we don’t know for certain. But it’s exciting to think about where the research could lead. Speaking of gut health, are there specific foods or nutrients that promote a healthy gut and, in turn, healthy behavior in dogs?

Dr. Liu: Based on the literature we have, we can’t yet say that this “XYZ” collection of bacteria equals a healthy gut, which therefore equals healthy behavior. Part of the challenge is that every individual’s microbiome is exceptionally unique so two healthy, happy dogs can have fairly different microbiome signatures.

However, we do know that part of what makes a “healthy gut” is the production of short-chain fatty acids, including butyrate, which is a key component of nourishing the gut cells and improving the gut barrier. Short-chain fatty acids (SCFAs) are created from the fermentation of undigested fibers. Thus, I do like to remind people that fiber is a really critical component of the domestic dog gut health, and I like to ensure that dogs in my care are receiving a really nice balance of soluble and insoluble fibers. When I have a really hard case, I like the results I see from using fiber-specific prescription kibble from Hills and Purina. For example, these can often be used to restore a chronic diarrhea case to normalcy. And then, when we’ve established that a fiber-specific food has helped, the owner can transition to their diet of choice and fiber supplementation of choice, or keep the kibble as a fiber supplementation - or just stay on the diet.

Sara: Fiber certainly seems to be a key part of maintaining gut health. I can see how it would have a big impact. What about prebiotics and probiotics? How might they influence a dog's behavior, and are there any specific types you recommend?

Dr. Liu: Prebiotics are basically fermentable foods for the bacteria in your dog’s large intestine, and this is usually some type of fiber like oligosaccharides, which are soluble plant fibers. Probiotics are the bacterial strains themselves. There are certain bacteria that show strong evidence in helping gut cell health, improving immune function, or may even reduce stress responses. Some of the strongest candidates that I have seen reported in the literature are: Bacillus coagulans, Saccharomyces boulardii, various Lactobacilli (though some recent findings in dogs show equivocal evidence), and various Bifidobacterium, including one strain that Purina uses for its Calming Care supplement.

Sara: It sounds like there are some promising options out there. What signs should pet owners watch for that could indicate their dog’s behavior is related to diet or gut health?

Dr. Liu: Reluctance to eat, especially breakfast, nausea or lip licking, vomiting, soft stools, diarrhea, flatulence, and reluctance to participate in activities due to internal pain can all be signs that your dog’s behavior is related to gut health issues.

Sara: If a dog is showing some of these signs, can dietary changes alone improve behavioral issues, or should they be combined with other forms of behavior modification?

Dr. Liu: Based on the data we have, no, dietary changes alone are unlikely to substantially improve behavioral issues based on changing the microbiome. Even old reports about changing protein levels or sources haven’t proven to be exceptionally meaningful. But improving overall GI health is certainly a helpful tool, and it’s important to ensure that the whole animal is capable of meeting the behavioral demands we’re asking. For example, I’m not going to train a dog to jump the meter jump if I have any questions about its musculoskeletal system, and I’m not going to use food reinforcement effectively if I have any questions about its gastrointestinal health. It is all intricately related, but science is still working out what levers we have to pull to make meaningful behavioral change.

Sara: That makes sense - to address the whole picture, not just one piece of it. But for pet owners who are hoping to improve their dog’s behavior through diet, where would you suggest they begin?

Dr. Liu: I recommend monitoring for any problems and having frank discussions with their primary vet. If their primary vet is not specially interested in diet or GI health, I recommend referral to a board-certified veterinary nutritionist. Veterinary nutritionists know the value of things like short-chain fatty acids on gut cell health and will be watching the scientific literature on microbiome carefully. That’s even why large companies like Purina and universities like Texas A&M have begun offering microbiome and dysbiosis testing as well.

Sara: Do you have any thoughts on tools like the DoggyBiome™ Gut Health Test for pet owners who want to better understand their dog’s gut health?

Dr. Liu: I can’t comment on private company products, especially not without robust published literature.

Sara: Fair enough. It’s important to wait for strong evidence before making recommendations. With that said, what are some of the most exciting recent developments or emerging trends in the field of canine gut health and its relationship to behavior? Are there any new studies or findings that pet owners should be aware of?

Dr. Liu: I strongly believe that this is a really interesting time for research into gut health. As organizations and researchers start taking a closer look at the microbiome of dogs—both healthy and atypical—they will generate a massive amount of data. And we are now living in a time where massive amounts of data can be efficiently analyzed through AI. We’re not there yet. The evidence is interesting but not causal, and the possibilities are just beginning.

Sara: The future certainly sounds promising. It will be fascinating to see where the research takes us. Finally, how can people find you if they want to learn more about your work?

Dr. Liu: Folks can contact me through my website: oaklandcanine.com, email me at oaklandcanine@gmail.com, or follow me on Instagram @oakland.canine.

Sara:Thank you for taking the time to walk us through all this, Dr. Liu. I’m sure Bay Woof readers will be interested to learn about any new developments as the research continues.