How much do vegan diets improve the health of dogs?

Pet food consumes at least 9% of all livestock globally, rising to 20% in nations such as the U.S. with high pet ownership. The environmental benefits of vegan pet diets were recently found to be game-changingly large. Most of these relate to dog food. But can dogs be healthy without consuming meat?

Dogs are biologically omnivores, and many companies now produce vegan dog food using plant, mineral and synthetic ingredients to supply all necessary nutrients. By 2024, 10 scientific studies had demonstrated good health outcomes in dogs fed vegan or vegetarian diets, and the British Veterinary Association had endorsed nutritionally sound vegan dog diets.

Yet no studies had calculated the size of the health benefits that might occur for average dogs, after controlling for age, sex, neutering status, breed size and exercise level—all factors that can affect dog health.

Now, veterinary Professor Andrew Knight and two colleagues have published the first study to control for all of these factors. After analyzing health outcomes for 2,536 dogs, including 336 fed a vegan diet for at least one year, they found decreases in the occurrences of seven general indicators of illness.

The study, "Vegan versus meat-based dog food: Guardian-reported health outcomes in 2,536 dogs, after controlling for canine demographic factors," has been published in Heliyon.

The researchers found that dogs fed vegan diets were less likely to need medication, medical diets or unusually high numbers of veterinary visits, were more likely to be assessed as healthy by dog owners and their veterinarians, had lower rates of illness, and fewer cases of health disorders when they were unwell. Reductions ranged from 14%–51% for average dogs, compared to dogs fed conventional meat-based diets.

All of these differences were statistically significant, meaning they almost certainly reflected true differences rather than random variation. Additionally, the odds of suffering from six specific health disorders fell by 50%–61% compared to dogs fed conventional meat. These included some of the most common health disorders in dogs: problems with body weight, ears, and the musculoskeletal and gastrointestinal system—which can cause conditions such as lameness and diarrhea.

Among the 22 most common health disorders found in a 2022 study of the same dogs, 11 were most common in dogs fed conventional meat, eight in dogs fed raw meat, and three most common in dogs fed vegan diets. Of dogs fed conventional meat, 49% were unwell, compared to 43% fed raw meat, and 36% fed vegan diets.

"Dogs fed vegan diets clearly had the best health outcomes in this very large-scale study, and these results are consistent with prior studies in this field," Professor Knight said.

"Nutritionally sound vegan diets offer extremely large environmental benefits, so this is very good news for dog owners who want to protect the environment while also maximizing their dogs' health. However, care should always be taken to ensure diets are nutritionally sound, by checking package labeling and purchasing from reputable pet food companies."