Behavioral Probiotics – Whole Dog Journal


The main job of the intestine is complicated and critical – extracting nutrients from food and removing waste products from the body – it is a marvel of engineering. In the last few decades, however, we have learned that the intestine is even more complex and astonishing than before: Researchers have found that the bacteria and fungi that live in the intestine can influence our behavior – or, more importantly for WDJ readers, our behavior dogs Behavior!

Gut feeling

The populations of bacteria, viruses, fungi, and microfauna that live on the bodies of dogs (and humans and rodents) are known as the Microbiome. You and your dog live in several different environments with different populations of tiny beings living on you: on the skin, in the mouth, in the vagina if you have one, and in the intestines.

The intestine is a type of tube that runs through you. The lining of this tube is a dynamic ecosystem of diverse bacteria that help digest your food, produce the nutrients it needs, and it turns out to have an effect on your emotions.

There is strong evidence of a relationship between gut and behavioral health. Inflammatory bowel disease in humans is linked to anxiety and depression. Autism is linked to bowel problems, as are many psychiatric illnesses. Antibiotics can kill many of the insects in our intestines, and when they do, the risk of developing an anxiety disorder increases. Intestinal infections can also increase the risk of anxiety disorders. We know that the gut microbiome can affect the stress response and that this relationship goes both ways – the stress response can also affect the flaws in our gut.

Normal, non-pathological personality traits also seem to change in harmony with our gut bacteria. A 2020 study looked at 655 people who completed online questionnaires and sent in stool samples. They found a decreased intestinal diversity in participants who reported having a high level of stress and in participants who described themselves as “more conscientious”. The researchers also found increased intestinal diversity in people with larger social networks. They also identified specific types of bacteria that are associated with people with certain personality traits.

These studies show correlations that gut and behavioral health go hand in hand. However, we still don’t know how this relationship works. Does Anxiety Cause Bowel Dysfunction? Or does a bowel dysfunction cause anxiety?

Studies in laboratory rodents show that fecal transplants (which populate the intestines of one mouse with the contents of the intestines of another mouse) can adapt the recipient’s behavior to that of the donor.

In one study, researchers stressed mice until their behavior changed to show fear. Then they gave a non-stressed population of mouse feces from these anxious donor mice. The previously unstressed population showed anxiety behavior, apparently only due to the transplantation of bacteria from stressed mice. Fascinating!


Okay okay Let’s discuss what is most important to us dog owners: Can we alter the bacterial populations in our dogs’ intestines to change their behavior?

We already frequently alter bacterial populations in dogs to encourage them Intestines Health, either through carefully curated commercial probiotic supplements or less carefully curated supplements in the form of foods like yogurt, kefir, or herb. Could we give probiotics that not only have gut health benefits, but behavioral health benefits too?

Several studies have addressed this issue in humans and laboratory rodents. Because a single The study is limited to what it can tell us – it is influenced by the exact methods used by the researchers as well as a healthy dose of chance – the best evidence we have is a Meta-analysis, A study that summarizes the results of many other smaller studies.

A meta-analysis by Reis et al. We looked at a number of studies on the effects of probiotics on human (14 studies) and laboratory rodents (22 studies) behavior. This summary study gives us the best evidence that probiotics can really change behavior.

This meta-analysis bundled the results of all laboratory animal studies and analyzed them together to determine the overall results. Overall, probiotics appeared to change the behavior of mice, not rats, and then only mice that were in some way unhealthy or stressed. (Some studies showed effects in rats or non-stressed mice, but overall results indicated that these studies showed only incidental effects.) As for humans, probiotics did not seem to have any effect in us either.

The researchers had some insight into why studies in rats and humans may not have shown any (or at least inconsistent) effect, while studies in mice showed:

* There may be a baseline fear below which probiotics won’t do much for you – you are already behaviorally healthy. Surprisingly, none of the human studies included subjects who actually suffered from anxiety!

* Measuring changes in people’s feelings is difficult and requires self-reporting tests, which are notoriously unreliable. Perhaps people taking probiotics felt better but weren’t aware of it. Studies suggest that if you have depression or persistent anxiety, you may experience measurable improvements before you become aware of them. However, measuring behavioral changes in laboratory rodents is more objective and therefore potentially more sensitive.

* Probiotics take time to work. Studies may not run long enough to see real change. A longer time means more effort. Only half of the studies included in this meta-analysis lasted at least eight weeks. Benefits in humans may have been found in long-term studies.

* Dose can be important. The doses of probiotic given to mice, rats, and humans weren’t too different, but when you take into account the massive differences in size between these species, they were very different. Since the smallest animals had the most pronounced effects, increasing the dose may make probiotics more effective in larger animals.

* The researchers suggested that it is possible that we humans may need to give doses dozens or hundreds of times higher than what we currently dose! This suggests that doses in dogs can also be low.

Decreasing Anxiety: Successful Probiotic Types

Ries et al., 2018, described the effectiveness of specific bacterial species in their meta-analysis. Just Lactobacillus rhamnosus showed an effect (in mice) in a pooled analysis. It has sometimes been effective in humans (but not in a pooled analysis). Other species that worked in some studies but not in a pooled analysis included:

• •L. helveticus

• •B. Adolescentis

• •B. longum (Strains R0175 and NCC3001)

• •L. rhamnosus combined with B. longum

Note: A type of bacteria L. casei, actually appeared to increase Anxiety.


In January 2019, Purina released the first probiotic to market for behavior modification in dogs, Calming Care. It includes B. longum, Strain BL999. (It also contains liver, and my dogs report it tastes great; they really lick it up.) Calming Care is the only behavioral probiotic tested in dogs, although many probiotics have been tested for gut (not behavioral) health were on the market.

Calming Care was tested by Purina, but the study was not published in a peer-reviewed journal. Summaries are available, but the detailed methods are not. This means that the specific methods for testing the probiotic are not public. This means that the results of the study are “difficult to interpret” in the classical research field – in other words, something could distort the results.

Here is what we do do Know: The study included 24 anxious Labrador Retrievers. Either dogs were given for six weeks B. longum BL999 (i.e. Calming Care) or a placebo; They were then tested for anxiety-like behavior, heart rate, heart rate variability, and salivary cortisol. (Details of the behavioral tests are not available.) The dogs were removed from the supplement for three weeks, after which the two groups were switched and each group received the other treatment (probiotics or placebo) for an additional six weeks. Both groups were tested a second time. The results were impressive:

* 22/24 treated dogs showed significant reductions in barking, jumping, spinning and stimulating compared to their behavior on placebo.

* Dogs treated 20/24 had less increases in salivary cortisol (a hormone that increases in response to stress) when they exercised and when exposed to anxiety-inducing stimuli, compared to their behavior on placebo.

* Dogs treated 20/24 had an increased heart rate variability (which is a sign of decreased stress) compared to placebo behavior.

Behavioral buyer aware

Unraveling the differences between various behavioral supplements marketed for dogs can be a challenge. Basic categories include:

• •Behavioral Probiotic: Currently, Calming Care is the only behavioral probiotic marketed for dogs.

• •Gut probiotics: Many probiotics are marketed solely for canine gut health. You can have behavioral advantages; They just haven’t been tested for it. Some examples are Fortiflora, Proviable, and Vetri Mega Probiotic.

• •Nutraceuticals: Some dietary supplements (like Solliquin and Composure) are marketed for behavioral health reasons. These are Not Probiotics; They work through different mechanisms.

• •Complex Dietary Supplements: Some dietary supplements contain both probiotics and nutraceuticals and are marketed for behavioral health. One example, Calm K9, is being marketed for the behavioral health nutraceuticals it contains. It also contains some probiotics, however Not the strains shown to have behavioral effects. Hence, it is best viewed as a nutraceutical when combined with a probiotic for intestinal health.


These numbers are very good – surprisingly good given the results of the meta-analysis discussed earlier. Two vets who prescribe Calming Care to their canine patients told me that it appeared to help about half of the dogs they tried on. However, they warned that it is worth trying, but its effects will not be as potent as that of a prescription drug on a dog with significant anxiety.

There is a gap between Purina’s research and the experience of the two clinicians I know – a gap that could be explained in several ways. The difference could be explained by the objective tests carried out by the Purina researchers compared to the owner reports used by the veterinarians. It is possible that all of the Labradors in the Purina study had a biologically similar form of fear that responds well to probiotics, but only occurs in half of the fearful dogs in the real world. Perhaps there was an issue with Purina’s study that caused the results to look better than they really were. The real question is, will Calming Care help Your Dog?

Probiotics are very safe and are unlikely to cause any ill effects. So it’s worth finding out. Purina recommends a trial of at least six weeks before deciding whether the supplement will work. However, it is worth doing the trial for at least eight weeks.

Some owners want to try probiotics for behavior but don’t want to use sedative care. Some dogs are allergic to liver (one of its ingredients). There are many probiotics that are marketed to help reduce human anxiety. I recommend working with your veterinarian to choose one of these. Your best bet is to pick one that contains B. longum (tested on dogs) and / or L. rhamnosus (tested on mice and humans) and Not contains L. casei (Can increase anxiety).


Behavioral probiotics can be a helpful addition to behavioral drugs, as they have done my anxious dog whose behavior has noticeably improved with Calming Care. Or they can have a mild effect in dogs that are not taking medication. Again, keep in mind that dogs with severe anxiety problems deserve a visit to a behavioral veterinarian to talk about medication, since probiotics alone aren’t strong enough to give them relief.

Our understanding of how the gut microbiome affects behavior is still in its infancy. Perhaps in the years to come we can assess a dog’s gut microbiome, predict how it will affect their behavior, and tailor a particular probiotic cocktail to steer them in the right direction. At the moment we mostly hike in the dark.

However, probiotics are very safe to use and can be a try if you are looking for a supplement to relieve your dog’s anxiety.

Jessica Hekman, DVM, Ph.D., is a researcher at the Karlsson Lab at MIT’s Eli and Edythe L. Broad Institute and Harvard, studying the genetics of dog behavior. She also teaches online webinars and courses on canine genetics.

Study references and resources

Johnson, Katerina V-A. “The composition and diversity of gut microbiomes are related to the personality traits of humans.” Human Microbiome Journal 15 (2020): 100069.

Li, Nannan, et al. “The transplantation of microbiota in the stool of chronically unpredictable donors of mice with mild stress influences the anxiety and depression-like behavior of recipient mice via the gut-microbiota-inflammatory-brain axis.” stress 22.5 (2019): 592-602.

Reis, Daniel J., Ilardi, Stephen S. and Punt, Stephanie EW. “The Anxiolytic Effects of Probiotics: A Systematic Review and Meta-Analysis of the Clinical and Preclinical Literature.” Plus one 13.6 (2018): e0199041.

Trudelle-Schwarz McGowan, R. “Using these” gut feelings “: Influence of BL999 (Bifidobacterium longum) on anxiety in dogs.” ACVB Symposium 2018.

Are you looking for a veterinarian to help you with behavioral medication for your dog? Visit the American College of Veterinary Behaviorists ( or the American Veterinary Society of Animal Behavior ( Both include practitioners who conduct online consultations when no one is around.

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