As concerns over the environmental and animal welfare impacts of meat-based pet foods grow, the development of alternative diets, particularly vegan options, has accelerated. However, despite the rapid growth of the vegan pet food market, skepticism remains regarding the suitability of these diets for dogs.

There has been limited large-scale research comparing the health status of dogs on plant-based versus meat-based diets. To help fill this gap, this study evaluates the health outcomes of dogs on vegan, raw meat, and conventional meat-based diets, while controlling for key medically relevant demographic variables such as age, sex, neutering status, breed size, and exercise levels.

Researchers surveyed 2,536 guardians about their dog’s health on different diets using an online questionnaire advertised through dog interest groups on social media. Although guardians may have had more than one dog, they were asked to report on a single dog who had lived with them for at least one year. Most dogs were fed a conventional meat diet (54%), followed by raw meat (33%) and vegan (13%) diets.

The researchers examined a number of illness indicators, including:

• How often the dog visited the veterinarian (with more visits being suggestive of ill health)
• Medication use (excluding routine vaccinations and parasite treatments)
• Whether the dog had progressed onto a therapeutic diet after initially being fed a vegan or meat-based diet
• The guardian’s opinion of their dog’s health
• The veterinarian’s assessment of the dog’s health (as reported by the guardian)
• For dogs with assessed health conditions, the number of health disorders they had

Based on these reports, the researchers calculated the proportion of unwell dogs in the sample, as well as the prevalence of 22 specific health disorders, including allergies, gastrointestinal concerns, and weight issues.

Using regression analyses, the researchers controlled for canine demographic factors to determine whether there were associations between the different diets and various health indicators. This was an important step, as initial results showed, for instance, that dogs on raw meat diets tended to be younger. As younger dogs also tend to have better health, this would have skewed the analysis — positively influencing the health outcomes of dogs fed raw meat diets, while negatively influencing those of dogs fed vegan diets.

These analyses revealed that dogs on vegan diets showed significantly better health outcomes across various measures compared to those fed conventional or raw meat diets. Vegan-fed dogs had 36% lower odds of requiring two or more veterinary visits a year compared to conventional meat-fed dogs, but 42% higher odds compared to raw meat-fed dogs. According to the researchers, this could reflect a reluctance of guardians feeding raw meat to seek veterinary care, possibly because veterinarians tend not to support raw diets due to concerns over nutritional deficiencies and pathogen contamination.

Additionally, vegan-fed dogs had 50% lower odds of receiving medication compared to conventional meat-fed dogs and 15% lower odds compared to raw meat-fed dogs. They were also 48% less likely to progress to a therapeutic diet than dogs on conventional diets, though they were 138% more likely to do so than dogs on raw meat.

Overall, 45% of the dogs in the sample were considered unwell according to guardian reports of veterinary assessments. Vegan-fed dogs had 48% and 40% lower odds of being unwell compared to conventional meat-fed dogs and raw meat-fed dogs, respectively. Unwell dogs on vegan diets experienced 14% fewer health disorders compared to those fed conventional meat and 8% fewer compared to those fed raw meat.

Despite these better outcomes, vegan-fed dogs were more likely to suffer from internal parasites (increased odds of 538% compared to conventional meat and 1,018% compared to raw meat). However, overall prevalence of internal parasites in these dogs was low (3%).

The study faced several limitations, primarily due to its reliance on guardian-reported data rather than controlled, objective assessments. This introduced possible bias and error, such as memory lapses or unconscious bias, though steps were taken to minimize these, including asking guardians to report veterinary assessments. Furthermore, dogs included in the survey were not exclusively fed the study diets, as they received various treats and supplements, which could affect the results.

The study was not fully representative, with under-representation of male respondents (7%) and a primarily U.K.-based sample (71%). The COVID-19 pandemic may have reduced veterinary visits and the use of medications or therapeutic diets, making the results more conservative. Additionally, the small sample sizes for certain health disorders may have limited the detection of statistically significant differences. Larger, more objective studies are needed to validate the findings, ideally using veterinary medical records and laboratory data.

Despite these limitations, the researchers conclude that nutritionally balanced vegan diets are the healthiest and least hazardous option for dogs, though they caution that all diets must be carefully formulated and produced to ensure they meet nutritional requirements and safety standards. This study, which builds on previous research, is helpful to those looking for evidence in the face of criticism or uncertainty about feeding vegan pet food to dogs.