Two years ago, a study was published claiming that a nutritionally sound vegan diet was “the healthiest and least risky dietary choice for dogs.”
We recently published a study that disputes these findings. Based on our analysis of the data used in the original studies, we argue that the association between diet and dog health (or, more precisely, owner opinions about their dog's health) is minimal at best.
To understand why we came to different conclusions, we need to understand how research on vegan dog food has been conducted to date, and why scientists have different views on the subject.
To date, several studies have been published on the health effects of vegan dog food, some of which are experimental cohort studies in which dogs are fed a vegan diet while monitoring various health indicators.
The longest-term study was a 12-month study published in 2024 in which 15 dogs were fed a dry food made with plant-based ingredients. All dogs remained healthy and had no apparent ill effects.
However, because there was no control group, we cannot infer that a plant-based diet is superior to a conventional diet.
Some published studies claim that dogs fed vegan foods are healthier than those fed other types of food, but these studies base their findings on information obtained from owner surveys.
The results of such a study depend on the owners' memories and perceptions – you are studying the owners' beliefs about their dog's health, not their dog's actual health.
The largest of these studies, published in 2022, collected data from over 2,000 dog owners, including information about both the owners and their dogs, including, of course, the type of food they fed their dogs.
Owners were asked to recall details of their dog's veterinary care (such as number of veterinary visits and medications) and to report how healthy they considered their dog to be. The results of the study suggested that dogs fed a vegan diet were healthier than those fed a conventional diet.
However, statistical analyses did not explore the effects of confounding factors such as dog age and breed, or owner characteristics.
What contribution does the new study make?
We further analysed the data from the original study using a range of statistical methods to effectively create a model that explained the data, testing the effects of dog and owner diet as well as other owner and dog variables.
For example, we looked at owner age, sex, and education status, as well as dog sex, breed, age, and neutered/neutered status. Some statistical models also included veterinary care variables.
We found that owners' opinions about their dog's health were most strongly associated with their dog's age: owners of younger dogs reported that their dogs were in better health. Other variables (such as owner's age, education level, and breed size) were also included in the analysis. For example, we found that younger owners reported that their dogs were in better health.
The models that best explained the data included veterinary care variables: for example, frequent visits to the vet were associated with poorer owner-reported health.
However, the association between vegan dog food and owner-reported health was minimal in all models, regardless of whether veterinary care variables were included, and the effect of vegan dog food disappeared when other variables were taken into account.
So why did the original study suggest there were positive effects of a vegan diet?
We can't say for sure, but that's what we looked at. It's possible that our study population was unusual and there were a lot more vegan dogs than we expected — about 1 percent of the general population, but as many as 13 percent of our study population. We also found that almost all of the owners who feed their dogs vegan food also follow a vegan or vegetarian diet.
This is concerning given that the findings are based on owner reports of their dog's health. Such memories and responses may be influenced, consciously or unconsciously, by the owner's beliefs. If you believe a vegan diet is best, this could have an unconscious effect on your perception of your dog's health.
What does this mean?
Our findings do not allow us to definitively say what type of diet is actually best for dogs, but despite the limitations of using owner report, there is no meaningful association between feeding a vegan food and dog health.
Instead, other variables are likely to be much more important.
Additionally, most commercial vegan dog foods are made in the same way as conventional diets: They follow the same manufacturing process, except that they only use plant-based ingredients.
Many of the ingredients are the same too. Given these similarities, it's surprising how one diet can have such a significant positive effect on your health.
Ultimately, what is most important to a dog's health is that their diet is properly formulated to meet all their essential nutrient needs, following evidence-based guidelines.
The published data to date has not identified any significant health concerns from feeding dogs a vegan diet, but there is also no evidence to suggest that there are any significant health benefits.
Alexander Jarman, Professor of Small Animal Medicine, University of Liverpool and Richard Barrett-Jolly, Senior Lecturer in Veterinary Neuroscience and Neuropharmacology, University of Liverpool
This article is republished from The Conversation under a Creative Commons license. Read the original article.
