PetEvidenceProject
TL;DR The Science Bottom Line References (15)

TL;DR — Plain language summary

Supplementation with probiotics to the diet of healthy adult dogs did not demonstrate a reduction in the development of gastrointestinal disease. However, specific probiotics have been found to improve certain molecular markers of gut health and the fecal microbiota.

The science behind it

15 references

Probiotics are live microorganisms, which are often considered “good” bacteria. Such bacteria have catapulted into the scientific spotlight in recent years due to the discovery of the intestinal microbiome and its role in health and disease, both in humans and animals. The intestinal microbiome is a delicate balance of bacteria with numerous types of microorganisms (predominantly bacteria) present. There is evidence that the microbiome influences systemic health, where an imbalance of these microorganisms (“dysbiosis”) may contribute to gastrointestinal or systemic health conditions, including chronic inflammatory disorders, autoimmune diseases, and even neurologic disease. It is therefore hypothesized that altering the intestinal microbiome such that there is more “good” bacteria, could reduce or improve signs of illness related to dysbiosis.

Probiotics have been proposed as a preventative and even therapeutic measure, by helping to restore the composition of the intestinal microbiome. Proposed mechanisms for these beneficial effects include restoring the balance by displacing “bad” bacteria, production of antimicrobial products (preventing growth of bad bacteria), improved barrier function of the intestinal tract (preventing “leaky” intestines), improved absorption of nutrients, and overall improved immune system function. Research into the role of probiotics is ongoing and considered to be in the early stages of evaluation. Numerous types of probiotics exist, whether they be individual species of bacteria, or a combination of different strains of bacteria. Of importance, findings of a study on a particular type of probiotic cannot be generalized to another type of probiotic since these can have differing effects on the microbiome. The quantity of microorganisms present, often indicated as CFU (colony forming units), as well as the viability of the microorganism in packaging, also play a role.

Within the veterinary medical literature exist few studies evaluating individual probiotic products both in health and disease states. As new research is produced, new products will likely be unveiled, hopefully with a positive impact on the health and well-being of our 4-legged companions.

The Bottom Line

There is great heterogeneity amongst the published literature with many studies evaluating different probiotics. Each probiotic can have slightly different effects on the canine microbiome and hence gut health. Multiple studies have demonstrated an improvement in fecal microbiota with probiotic administration, though this presumed beneficial effect has not yet been translated to clinically measurable outcome measures (e.g. quality or quantity of life). Probiotics have demonstrated safety when given at labeled doses in healthy animals. Therefore, it is unknown if routine supplementation with a probiotic to dogs without signs of underlying gastrointestinal disease provides either a short or long term health benefit. Fortunately, this is a popular research topic and more informative studies may become available in the near future.

Of note, this review does not include the effects of probiotics in dogs with underlying gastrointestinal disease or other health conditions. While there has been demonstrated improvement in dogs with diarrhea related to administration of certain probiotics, please consult your veterinarian for further information and guidance.

References 15

  1. 1

    Jensen AP, Bjørnvad CR. Clinical effect of probiotics in prevention or treatment of gastrointestinal disease in dogs: A systematic review. Journal of Veterinary Internal Medicine 2019.

    View source
  2. 2

    Moxon R, Goumas M, Hunt R, England G.. Randomised controlled trial finds no evidence that a synbiotic improves health in assistance dog puppies. Vet Rec 2026.

    View source
  3. 3

    Garcia-Mazcorro JF, Lanerie DJ, Dowd SE, et al.. Effect of a multi-species synbiotic formulation on fecal bacterial microbiota of healthy cats and dogs as evaluated by pyrosequencing.. FEMS Microbiol Ecol 2011.

    View source

Senior Dog Considerations

Can help support digestive health in senior dogs, especially during dietary changes or stress.

Visit Senior Dog Corner

Related Reviews

Probiotics (skin)

Research Snapshot

15 references on this page
C

Emerging / Inconclusive

Limited or low quality studies and/or conflicting study results.

Meta-analysis and many observational studies, many investigations focused on markers of gut health. Likely difficult to quantify benefits

Evidence Quantity high
Evidence Quality medium
Safety Risk low
How we grade evidence
Grade Meaning
A Highly likely/Proven Benefit
B Probable Benefit
C Emerging / Inconclusive
D Weak
F No evidence of benefit, possible harm
n/a Insufficient data

Also in Digestive Health

Updated February 25, 2026