Plant-Based Dog Food: What 14 Peer-Reviewed Studies Show

The science of plant-based nutrition for dogs has evolved rapidly. What was once a niche topic with limited research is now the subject of peer-reviewed studies from institutions including the University of Illinois, the University of Guelph, and the Waltham Petcare Science Institute. From gut microbiome mapping to controlled feeding trials, researchers are building a clearer picture of how plant-based diets affect canine health—and the results are worth paying attention to.

This article rounds up the most significant findings from the past five years, with a focus on two areas where the research has been especially active: gut health and longevity. Every study cited is published in a peer-reviewed journal, and we've linked to the originals so you can read them yourself.

The Canine Gut Microbiome: New Research, New Understanding

Your dog's gut is home to trillions of bacteria that influence everything from digestion to immune function to mood. The composition of this microbiome—and the metabolites it produces—is shaped heavily by diet. A wave of recent studies has started to clarify exactly how.

Mapping the canine gut for the first time

In January 2026, researchers at the Waltham Petcare Science Institute published the most comprehensive catalog of the canine gut microbiome ever created. Analyzing fecal samples from 107 healthy dogs across the U.S. and Europe, the team reconstructed 5,753 bacterial genomes and identified 982 previously unknown strains, 89 novel species, and 10 novel genera. Prior to this work, only about 25% of bacteria in the canine gut had been formally identified. The new catalog accounts for over 80% of the canine gut microbiome and increases mapping rates by approximately 70% ^[1].

A key finding: the dog gut microbiome is dominated by many of the same fiber-fermenting bacterial phyla found in humans—particularly Firmicutes and Bacteroidetes—suggesting that canine and human guts respond to plant-based dietary fiber through shared biological mechanisms ^{[1, 2]}.

How plant-based diets shift the microbiome

A 2024 study published in Frontiers in Microbiology directly compared the fecal microbiota of healthy adult dogs fed plant-based (vegan) diets to those fed animal-based diets. The researchers—including board-certified veterinary nutritionist Dr. Sarah Dodd—found that plant-based diets produced measurable changes in gut microbiota composition. The study noted shifts in bacterial populations consistent with increased fiber fermentation, though the authors were careful to note that longer-term studies are needed to understand the full implications of these changes ^[3].

Fiber, SCFAs, and why they matter

Short-chain fatty acids (SCFAs)—particularly butyrate, propionate, and acetate—are produced when gut bacteria ferment dietary fiber. These compounds play a surprisingly important role in canine health. A comprehensive 2024 review in Nature Reviews Immunology describes how SCFAs support intestinal barrier function, regulate immune responses through multiple pathways, and reduce inflammation throughout the body ^[4].

A 2025 study in mSystems examined how different types and amounts of dietary fiber affect the gut microbiome and metabolome in healthy dogs. The researchers found that fiber intake was significantly correlated with SCFA production—particularly acetic and propionic acids—and that higher-fiber diets enriched populations of beneficial bacteria including Butyricicoccus pullicaecorum and members of the phylum Bacteroidetes ^[5]. A follow-up commentary in the same journal emphasized that these findings mirror human research, where fiber-rich diets support microbial diversity and SCFA production for improved gut and immune health ^[6].

In the context of plant-based dog food specifically, a 2023 study from the University of Illinois found that dogs consuming vegan diets had higher fecal SCFA concentrations and lower concentrations of putrefactive compounds (phenol and indole, which are byproducts of protein fermentation) compared to dogs eating chicken-based kibble ^[7].

Digestibility and Nutritional Adequacy: What the Feeding Trials Show

One of the most common concerns about plant-based dog food is whether dogs can actually digest and absorb nutrients from plant ingredients as effectively as from animal ingredients. Several controlled feeding trials have addressed this question directly.

University of Illinois: amino acids and metabolic markers

In 2023, researchers at the University of Illinois led by Dr. Kelly Swanson published two companion studies evaluating vegan dog diets. The first used the precision-fed cecectomized rooster assay (a validated model for amino acid digestibility) and found that the majority of essential amino acids in vegan diets had digestibility values above 80%, meeting AAFCO requirements for adult dog maintenance ^[8].

The second study tested the diets in beagles for three weeks and measured blood chemistry, fecal quality, and microbiome composition. The findings: all diets were highly digestible, blood metabolites stayed within reference ranges, and dogs on the vegan diets had significantly lower blood cholesterol and triglyceride levels—a finding the researchers noted could benefit overweight dogs ^[7].

University of Guelph: vitamin D and bone health

A 2023 randomized trial from the University of Guelph, led by Dr. Sarah Dodd, enrolled 61 healthy adult dogs: 31 fed a plant-based diet and 30 fed a commercial meat-based diet for three months. The study specifically examined whether vitamin D2 (the plant-derived form) could maintain serum vitamin D levels and bone mineralization compared to vitamin D3 (animal-derived). The results showed that bone mineral content and density did not differ from baseline values, and health status was maintained in dogs on the plant-based diet ^[9].

A follow-up study from the same research group (published 2023 in Frontiers in Animal Science) examined macronutrient digestibility and found that extruded plant-based diets demonstrated similar nutrient digestibility to conventional animal-based diets when processed using standard manufacturing methods ^[10].

And in 2025, a further analysis published in the Journal of Animal Science examined the fecal metabolome of dogs from the same cohort, finding metabolite shifts associated with increased polysaccharide digestion in the plant-fed group—indicating the dogs were actively and efficiently processing the plant-based ingredients ^[11].

Longevity and Health Outcomes: What the Population Studies Show

While controlled feeding trials examine specific biological markers over weeks or months, population-level surveys help researchers understand how dietary patterns relate to broader health outcomes over longer periods. Several large-scale studies have explored the relationship between plant-based diets and canine health.

The largest study to date: 2,536 dogs

In 2022, a study published in PLOS ONE surveyed 2,536 dog guardians who provided data on dogs fed conventional meat (54%), raw meat (33%), or vegan (13%) diets for at least one year. Researchers evaluated seven general indicators of ill health and the prevalence of 22 specific health disorders. The study found that dogs on plant-based diets had the lowest overall prevalence of health disorders at 36%, compared to 43% for raw meat and 49% for conventional meat diets ^[12].

The researchers were transparent about limitations: dogs in the raw meat group tended to be younger (which is associated with better health outcomes), and the data was guardian-reported rather than collected through direct veterinary examination. These are important caveats, and the authors noted them clearly ^[12].

Guardian-reported longevity data

A 2022 study published in Research in Veterinary Science surveyed 1,189 dog guardians in North America, including 357 feeding solely plant-based diets for an average of three years. The study found that owners feeding plant-based diets reported fewer health disorders—specifically with respect to ocular, gastrointestinal, and hepatic conditions—and that dogs on plant-based diets were reported to have greater longevity than those on meat-based diets ^[13].

As with all survey-based research, these findings reflect owner perceptions and may be subject to selection or reporting bias. The study's authors were explicit about this, noting that objective research is required to determine whether plant-based diets truly affect canine health outcomes. Still, the consistency of findings across multiple independent surveys is noteworthy.

A systematic review of the evidence

In 2023, a systematic review published in Veterinary Sciences evaluated 16 studies on the health impacts of plant-based diets for dogs and cats. The review concluded that there was no overwhelming evidence of adverse effects and that there was some evidence of benefits. The authors recommended that guardians who wish to feed plant-based diets take a cautious approach using commercially produced diets formulated to meet the nutritional needs of the species ^[14].

Connecting the Dots: From Gut Health to Whole-Body Health

The emerging picture from this body of research suggests a plausible biological pathway: plant-based diets provide more dietary fiber than conventional meat-based kibble, which feeds beneficial gut bacteria that produce SCFAs. Those SCFAs, in turn, support intestinal barrier integrity, modulate immune function, and reduce systemic inflammation—all of which may contribute to the improved health outcomes reported in population studies.

It's a hypothesis, not a proven causal chain—and researchers are clear about that distinction. But the individual links in this chain are increasingly well-supported. The canine and human gut microbiomes share enough biology that insights from one species can meaningfully inform research in the other ^{[2, 5]}. In humans, the link between dietary fiber, SCFA production, and improved health outcomes is well established ^[4]. The emerging canine research is heading in the same direction.

What This Means for You and Your Dog

If you're considering a plant-based diet for your dog—or already feeding one—the research is encouraging. Here's what the science supports, along with what we still don't know:

What the research supports:

• Properly formulated plant-based dog diets are nutritionally adequate, with amino acid digestibility above 80% and blood metabolites maintained within reference ranges ^{[7, 8, 9]}
• Plant-based diets increase fiber-fermenting gut bacteria and SCFA production, which are associated with improved gut and immune health ^{[3, 5, 7]}
• Multiple independent population studies report reduced health disorders and improved longevity in dogs fed nutritionally complete plant-based diets ^{[12, 13]}
• Controlled trials demonstrate maintained bone health, vitamin D status, and body composition in dogs fed plant-based diets ^{[9, 10]}

What we're still learning:

• Long-term controlled feeding trials (beyond 3–12 months) are still needed to confirm health benefits over a dog's full lifespan
• Most longevity data comes from guardian-reported surveys, which may reflect selection or reporting bias
• Individual variation in microbiome composition means that some dogs may respond differently to dietary changes than others ^[5]
• The 2024 microbiome study authors noted that future research should examine the long-term effects of plant-based diets on the canine gut microbiome ^[3]

The consistent thread across every study: the qualifier "properly formulated" matters. Commercial plant-based diets designed by veterinary nutritionists to meet AAFCO standards consistently outperform homemade options. If you're evaluating a plant-based food, look for an AAFCO statement, formulation by a qualified veterinary nutritionist, and transparency about nutritional testing.

Frequently Asked Questions

What does the latest research say about plant-based diets and dog gut health?

A 2024 study in Frontiers in Microbiology found that dogs fed plant-based diets showed changes in gut microbiota composition, including increased fiber-fermenting bacteria that produce beneficial short-chain fatty acids ^[3]. A 2025 study in mSystems demonstrated that dietary fiber from plant sources significantly increases SCFA production in dogs, which supports intestinal health and immune function ^[5].

Can dogs live longer on a plant-based diet?

A 2022 study in Research in Veterinary Science found that dog owners feeding plant-based diets reported greater longevity and fewer health disorders in their dogs ^[13]. A larger 2022 PLOS ONE study of 2,536 dogs found that plant-based dogs had the lowest prevalence of health disorders across three diet groups ^[12]. These findings are based on guardian-reported data, and more controlled long-term clinical trials are needed to confirm these patterns.

Are plant-based dog foods nutritionally adequate?

Yes, when properly formulated. A 2023 University of Illinois study found amino acid digestibility above 80% for most essential amino acids in vegan dog diets, meeting AAFCO requirements ^[8]. A 2023 University of Guelph trial found that plant-based diets maintained bone density, vitamin D levels, and overall health over three months ^[9]. The key factor is formulation by qualified veterinary nutritionists.

What are short-chain fatty acids (SCFAs) and why do they matter for dogs?

SCFAs—including butyrate, propionate, and acetate—are produced when gut bacteria ferment dietary fiber. A 2024 review in Nature Reviews Immunology shows that SCFAs support intestinal barrier function, regulate immune responses, and reduce inflammation ^[4]. Dogs fed fiber-rich plant-based diets have been shown to produce higher levels of SCFAs compared to those on conventional diets ^[7].

How similar is the dog gut microbiome to the human gut microbiome?

Highly similar in composition. A 2018 study in Microbiome found shared dominant phyla and similar genetic material between human and canine gut microbiomes ^[2]. The 2026 Waltham catalog confirmed that many bacterial species in the dog gut are the same fiber-fermenting species found in humans ^[1]. Both species respond to dietary fiber interventions in analogous ways.

What should I look for in a plant-based dog food?

Look for an AAFCO statement confirming the diet is complete and balanced, formulation by a qualified veterinary nutritionist, transparency about ingredient sourcing and nutritional testing, and supplementation of key nutrients including taurine, L-carnitine, and vitamin D. Learn more about what to look for in plant-based dog nutrition.

Further Reading from Petaluma

• Is Vegan Dog Food Healthy? A Nutritionist-Backed Guide
• Plant-Based Proteins for Dogs: Full Ingredient Breakdown
• Essential Amino Acids in Plant-Based Dog Food
• Veterinarian FAQ with Dr. Blake Hawley
• Petaluma's Nutrition Page

Citations

1. Castillo-Fernandez J, Gilroy R, Jones RB, et al. Waltham catalogue for the canine gut microbiome: a complete taxonomic and functional catalogue of the canine gut microbiome through novel metagenomic based genome discovery. Microbiome. 2026;14:25. doi:10.1186/s40168-025-02265-w
2. Coelho LP, Kultima JR, Costea PI, et al. Similarity of the dog and human gut microbiomes in gene content and response to diet. Microbiome. 2018;6:72. doi:10.1186/s40168-018-0450-3
3. Liversidge BD, Gomez DE, Dodd SAS, et al. Comparison of the fecal microbiota of adult healthy dogs fed a plant-based (vegan) or an animal-based diet. Frontiers in Microbiology. 2024;15:1367493. doi:10.3389/fmicb.2024.1367493
4. Mann ER, Lam YK, Uhlig HH. Short-chain fatty acids: linking diet, the microbiome and immunity. Nature Reviews Immunology. 2024;24(8):577-595. doi:10.1038/s41577-024-01014-8
5. Bhosle A, Jackson MI, Walsh AM, Franzosa EA, Badri DV, Huttenhower C. Response of the gut microbiome and metabolome to dietary fiber in healthy dogs. mSystems. 2025;10(1):e00452-24. doi:10.1128/msystems.00452-24
6. Frame LA. Fiber, microbiomes, and SCFAs: insights from companion animal models to inform personalized nutrition. mSystems. 2025;10(1):e01454-24. doi:10.1128/msystems.01454-24
7. Roberts LJ, Oba PM, Swanson KS. Apparent total tract macronutrient digestibility of mildly cooked human-grade vegan dog foods and their effects on the blood metabolites and fecal characteristics, microbiota, and metabolites of adult dogs. Journal of Animal Science. 2023;101:skad093. doi:10.1093/jas/skad093
8. Roberts LJ, Oba PM, Utterback PL, Parsons CM, Swanson KS. Amino acid digestibility and nitrogen-corrected true metabolizable energy of mildly cooked human-grade vegan dog foods using the precision-fed cecectomized and conventional rooster assays. Translational Animal Science. 2023;7(1):txad020. doi:10.1093/tas/txad020
9. Dodd SAS, Adolphe JL, Blois SL, et al. Efficacy of vitamin D2 in maintaining serum total vitamin D concentrations and bone mineralization in adult dogs fed a plant-based (vegan) diet in a 3-month randomized trial. British Journal of Nutrition. 2023;130(11):1882-1893. doi:10.1017/S0007114523001952
10. Liversidge BD, Dodd SAS, Adolphe JL, Gomez DE, Blois SL, Verbrugghe A. Extruded diet macronutrient digestibility: plant-based (vegan) vs. animal-based diets in client-owned healthy adult dogs and the impact of guardian compliance during in-home trials. Frontiers in Animal Science. 2023;4:1288165. doi:10.3389/fanim.2023.1288165
11. Liversidge BD, Dodd SAS, et al. The fecal metabolomic signature of a plant-based (vegan) diet compared to an animal-based diet in healthy adult client-owned dogs. Journal of Animal Science. 2025;103:skaf053. PMC12056932
12. Knight A, Huang E, Rai N, Brown H. Vegan versus meat-based dog food: Guardian-reported indicators of health. PLOS ONE. 2022;17(4):e0265662. doi:10.1371/journal.pone.0265662
13. Dodd SAS, Dewey C, Khosa D, Verbrugghe A. Owner perception of health of North American dogs fed meat- or plant-based diets. Research in Veterinary Science. 2022;149:36-46. doi:10.1016/j.rvsc.2022.06.002
14. Domínguez-Oliva A, Mota-Rojas D, Semendric I, Whittaker AL. The impact of vegan diets on indicators of health in dogs and cats: A systematic review. Veterinary Sciences. 2023;10(1):52. doi:10.3390/vetsci10010052