Vegan diets are healthier and safer for dogs than conventional meat-based diets, according to the largest study to date, as long as they are nutritionally complete.
The diet and health of more than 2,500 dogs were followed over a year using surveys completed by their owners. These assessed seven general indicators of health, such as multiple visits to the vets, and 22 common illnesses.
The researchers found that, for example, almost half the dogs fed conventional meat-based diets required non-routine medication but only a third of the dogs fed vegan diets did so. A separate study in 2021 found that dogs found vegan diets just as tasty as regular dog food.
Some of the dogs in the study were fed raw meat diets and these were marginally more healthy than the vegan dogs overall. However, this may have been because they were on average a year younger.
The damaging impact of western societies’ overconsumption of meat on the environment and people’s health has become clear in recent years, as well as rising concerns over how farm animals are treated.
There are about 470m pet dogs in the world and an increasing number of pet owners are now considering changing their animal’s diets as well. About $9bn (£6.9bn) of vegan pet food was sold worldwide in 2020 and the sector is growing fast.
“Our study is by far the largest study published to date,” said Prof Andrew Knight, at the University of Winchester, UK, and who led the study. “It revealed that the healthiest and least hazardous dietary choices for dogs are nutritionally sound vegan diets.”
“The raw meat diet appeared to have marginally better health outcomes,” he said. “But those dogs were significantly younger, which gives them a health advantage. A substantial body of prior studies have also shown that raw meat diets are much more contaminated with pathogenic bacteria and parasites.”
The study, published in the journal Plos One, analysed surveys completed by 2,536 dog owners about a single animal. Just over half ate conventional meat-based diets, a third were fed raw meat and 13% had vegan diets.
Among the findings were that 17% of dogs on conventional diets had four or more visits to the vet over the course of a year, compared with 9% for those on vegan diets and 8% for those on raw meat diets. The percentage of dogs reported to have suffered from health disorders was 49% for the conventional diet, 43% for the raw meat diet and 36% for the vegan diet.
Survey-based studies cannot reveal the reasons for their results but Knight suggested weight problems might be an important factor: “One of the most common health problems for dogs is being overweight or obese and it is unfortunately common that when we do tests on the commercial meat-based diets, there are more calories.”
“We also know the health hazards associated with overconsumption of meat and dairy for people and it’s often the same ingredients,” he said, although in some countries pet food can contain meat deemed not fit for human consumption.
Further research is needed to confirm the findings. “The key limitation of our study is that we didn’t have a population of animals locked up in a research facility and fed one specific diet without any alteration,” Knight said. “We studied what real dogs in normal homes ate and their health outcomes. It gives us a good indication as to what the outcomes are for dogs in the real world.”
Justine Shotton, the president of the British Veterinary Association, said: “There is a lot of ongoing research in the field of vegan dog diets and this paper adds to the body of evidence supporting its benefits. However, there is currently a lack of robust data mapping the health consequences of feeding a vegan diet to a large number of dogs over many years, so we look forward to seeing further research on whether this can meet a dog’s dietary requirements over the long term.”
“Although we would not recommend it, it is theoretically possible to feed a dog a vegetarian diet, but owners would need to take expert veterinary advice to avoid dietary deficiencies and associated disease,” she said.
Most of the respondents to the survey were in the UK and other European countries and more than 90% were women, but Knight said this was unlikely to have caused a systematic bias. Knight, who follows a vegan diet himself but does not own a dog, devised and led the peer-reviewed study, which was funded by the charity ProVeg.