Can Dogs Fare Well on Plant-Based Diets?

The British quiz show "QI" once gave contestants a photo of a family with two children, a car, and a dog and asked what they could do to reduce their carbon footprint. You likely answered as everyone does, “Get rid of the automobile!”

But such obvious answers rarely make good drama, and what everyone misses is that the dog likely creates more greenhouse gas emissions than the car. It does so through its diet, likely high in factory-farmed animal content.

Source: Adam Kontor, Pexels

The Undoing of the Vegetarian?

There are about 150 million companion dogs and cats in the U.S. and close to 1 billion worldwide. For most, the conventional pet diet is meat-heavy, as pet foods in the U.S. use 1.83 million tons of meat annually.

In fact, pets eat an estimated one-fourth of all meat in the U.S., the equivalent of the meat eaten by 26 million Americans. As their own nation, pets would constitute the fifth largest country in terms of animal protein consumed. And these trends show no sign of abating, as the number of companion dogs in the U.S. has risen significantly in the last decade or so and is expected to increase from 85 million in 2020 to 100 million in 2030.

For some vegetarians or vegans—who often dearly love animals—the situation poses a tragic tradeoff between two sacred values: 1) feeding one’s dog or cat an animal-based diet that may be perceived as best promoting their well-being with 2) concerns over animal welfare and environmental degradation threatened by such diets. Basically, they want to feed them a proper diet but may feel terrible about what that entails.

In 2013 and 2014, I published several articles where I dubbed this the “vegetarian’s dilemma.” To the chagrin of some vegetarians, their household with a companion animal may consume more meat than their neighbors who eat meat but have no pets. What logic does this make?

Since the time of my research, philosopher Josh Milburn has explored the issue in Just Fodder: The Ethics of Feeding Animals, where he uses the term “the animal lover’s paradox.” In his words, through pet diet, “animal lovers… typically create more nonhuman animal death and suffering than they would if they did not keep companions.”

My work found that this dilemma was especially distressing and guilt-provoking for those abstaining from meat for ethical reasons, as they would be especially sensitive to nonhuman animal suffering. To paraphrase Milburn, if it’s wrong to support the meat industry in our own diet, how can it be right to support them to feed our companions? And yet, this is what many vegetarians presumably do.

In my research, I found that for those living with cats, some relief was offered by rationalizing that meat is necessary for their diet. This isn’t quite clear, but the perception is what matters in helping to appease people’s consciences.

Source: Mart Production Pexels

My focus here lies with dogs though, as it is even less apparent that they need meat to survive and thrive. What does the research say since my 2013 paper? Can dogs fare well on a plant-based diet, one that has been termed “K9PBN” (canine plant-based nutrition)?

Fortunately, evidence has been steadily increasing in the last few years, probably reflecting greater consumer interest. There are two general types of studies: 1) those asking dog guardians to indicate what they feed their dog and report health outcomes; and 2) those tracking diet and assessing objective physiological indicators of well-being.

Self-Report Assessments of Dogs on K9PBN

• Recent research led by veterinarian and Director of the Centre for Animal Welfare at the University of Winchester Andrew Knight surveyed 2,639 dog guardians. Dogs fed conventional diets appeared to fare worse on seven indicators of ill health (e.g., unusual numbers of veterinary visits, medication use, percentage of unwell dogs, etc.) than those fed K9PBN or raw meat. Forty-nine percent of the conventional meat diet were reported to have suffered from health disorders compared to 36 percent fed a vegan diet.
• A study published in December 2022 by a group of researchers from the Ontario Veterinary College at the University of Guelph surveyed 1,189 North American dog guardians, with 56 percent feeding their dogs a meat-based diet and 30 percent K9PBN. Guardians of dogs fed strictly K9PBN reported fewer health conditions, and no health disorder was more common among the K9PBN group. Fewer of the plant-based dogs were reported to be constipated or having hard stool, and previous dogs reportedly fed a K9PBN diet lived 1.5 years longer than dogs fed meat.
• In 2022, the English veterinary researcher Mike Davies surveyed 100 individuals whose dogs were vegan for 3-12 months. Appetite and weight were unaffected. There were improvements noted in activity, fecal consistency, frequency of defecation, flatus frequency, flatus antisocial smell, coat glossiness, dandruff, redness of the skin, itchiness, and anxiety.
• A survey of 250 dog guardians in Europe revealed far more positive than negative consequences to switching to K9PBN. Disproportionate improvements were noted in overall health, activity level, dermatological conditions, coat health and shine, odor, dental health, and reduced bad breath.

These subjective reports—while favorable—are susceptible to biased reporting because guardians switching to plant-based diets are motivated to justify their choice and likely feel better about the diet themselves. As such, it is important to corroborate self-reports with objective indicators.

Source: Mikhail Nilov Pexels

Objective Physiological Indicators of Well-Being of Dogs on K9PBN

• In a 2023 paper, a team of veterinary researchers examined fifteen healthy, adult dogs in Los Angeles who were fed K9PBN for a year. Objective medical indicators such as complete blood count, blood chemistry, cardiac biomarkers, plasma amino acids, and serum vitamin concentrations, revealed that the dogs maintained good health.
• Cavanaugh et al. (2021) examined physiological differences before and after 34 client dogs switched to K9PBN. The transitioned dogs did not develop any amino acid or taurine deficiencies, their cardiac ultrasounds were unaltered, and blood cell type and blood enzyme analysis remained normal.
• Semp examined 20 dogs fed K9PBN for at least six months and found no abnormalities during clinical assessment. No diseases could be found that were linked to diet, and results of blood assessment showed no significant differences in all tested parameters in K9PBN dogs compared to those fed a conventional diet.
• Keimer compared blood nutrient levels for nine indicators among 20 dogs fed a vegan diet and 20 fed a conventional animal-based diet. Eleven traditional diet dogs had deficiencies compared to only two vegan-fed dogs (which were lower in folic acid, likely from an infection that was diagnosed shortly after the blood draw).

These samples are obviously small, but the results appear promising for K9PBN.

Incorporating older research as well, a 2023 meta-analysis examined sixteen studies investigating the effect of a vegan diet on cat and dog health. Putting aside small samples and potential bias affecting self-report studies, the researchers concluded that there was little evidence of adverse health effects and some evidence of benefits that was relatively consistent across the individual studies.

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Conclusion

Based on the latest research, therefore, it appears that vegetarians have nothing to fear in giving their dog a plant-based diet.

This is consistent with expert nutritional analysis. The University of Guelph team cited earlier concluded an assessment of plant-based dog diet this way: “Dogs have dietary requirements for energy and essential nutrients, but they do not have a recognized requirement for animal-derived ingredients per se.” The European Pet Food Industry Federation states that “dogs are omnivores and can adapt to a well-balanced vegetarian diet.” Both groups warn, however, that special care should be taken to ensure that nutrient requirements are met, especially arginine, lysine, methionine, tryptophan, taurine, iron, calcium, zinc, vitamin A, and some B vitamins.

In doing so, ethical vegetarians could eliminate a major gap between their values and actions.