A recent study made the headlines. A peer-reviewed analysis of around 2,500 pets finds vegan dogs visit the vet less often and require fewer medications.

Looks amazing doesn’t it, a diet that is healthier for dogs while also saving the environment? Is it as good as it seems? Let’s investigate.

We just want our pets to be healthy

At the heart of every owner’s decision – especially with the surprisingly emotive topic of diet – is the desire to provide the very best for our beloved dogs. Many of these decisions, though, can also be based or swayed by our own bias and beliefs. This is confirmed by the authors of the study who stated 

‘Our results affirmed the importance of pet health to guardians. Among 2,596 respondents, health and nutrition was the factor considered most important in purchasing decisions.

We are increasingly aware of the global climate crisis. As such Veganism is growing, supported by the arguments that it may be better for our health, better for animal health and welfare and better for the environment. Naturally, these ideas will also filter into our decision making for our pets. Thus vegan diets for dogs have been seen to grow in recent years. This is agreed in the study that states:

‘Vegan diets are among a range of alternative diets being formulated to address increasing concerns of consumers about traditional pet foods, such as their ecological ‘pawprint’, perceived lack of ‘naturalness’, health concerns, or impacts on ‘food’ animals used to formulate such diets’

Dogs are omnivores, and as such can technically live on a vegan diet – and there are many that do. However, we are in the infancy of knowledge about these diets and their effect on the health and longevity of dogs.

Bold scientific journalism can be far reaching and could be quite damaging if the evidence isn’t presented in an open and transparent way.

Conflict of interest

First thing to note is the conflicts of interest. Notably in that the researcher that devised and led the peer-reviewed study, Andrew Knight, follows a vegan diet himself but does not own a dog. Moreover, the study was funded by the charity ProVeg. A charity whose aim is to raise awareness of the importance of plant-based food for people, animals, and the planet through their campaigns. This effort should be commended, as each individual does have a responsibility to ensure the health of people, animals and our planet. But this does suggest that there might be a certain bias towards a plant-based diet in results. This may be supported by some of the language used by the authors, who describe a “lower risk” of disease states where that is associated with conventional food; but a “lowered risk” (implying improvement rather than correlation) when discussing the vegan-fed animals.

On the other hand, the sample size was good with 2,639 dogs (some being excluded for various reasons throughout the process) and their owners being included in the study. Usually, larger numbers of participants mean a more reliable study.

Downfalls of a survey

Surveys may suffer from issues that can affect the ability to draw robust conclusions from the data received and analyzed. As this study was indeed based on a survey, we need to investigate potential downfalls…

Respondent Profile

2,610 human respondents who provided their sex, 92% (2,412) identified as females. While a predominance of female respondents is common in these sorts of survey, it may suggest that the people answering the questions aren’t representative of the population. Linked to the fact that demographics are important factors in how people behave, and that different groups are susceptible to different types of bias when responding to surveys. We should be aware that care must be taken in generalising the results to the whole pet owning population. 

There were also already quite a few respondents that were taking an interest in vegetarianism or veganism; this could have affected results due to potential unconscious bias. With vegan (22%, 586), reducetarian (omnivore reducing animal product consumption) (21%, 567), vegetarian (10%, 266) making up 53 % of respondents. This is significantly higher than the estimated population of the UK who are currently vegan; which is estimated at about 7%. Given that the survey was all about self-reported health status of dogs, any such biases may make interpretation of the results more difficult. Especially if the researchers share some of these biases themselves.

Sample Issues

In the study there was a much larger sample size for conventional compared to vegan which can lead to some discrepancy.

Of the 2,639 dog guardians responded -2,612 indicated the main diet their dog was maintained on. 2,536 dogs were jointly maintained on the three main diets identified. These were:

  • Conventional meat (1,370–54%)
  • Raw meat (830–33%)
  • Vegan Diet (336–13%) 

The main issue here is that ideally when looking for robust data we need there to be no significant difference between the groups presented. A larger sample size will be better representative of the population and will hence provide more accurate results. In this case the difference between the 54% of Conventional meat diets and only 13% Vegan could have caused some issues in how we draw robust conclusions. In this case, the 336 vegan feeding respondents aren’t a big enough number to be able to generalise accurately about the whole vegan-fed population of dogs; you need at least 384 responses for high enough accuracy for that.

Certain ideologies mean you are less likely to visit a vet – at all!

Interestingly, people holding certain ideologies in human health can make people less likely to visit a doctor or less likely to access conventional medicine and experience poorer patient outcomes. This can be seen in animals too. This theory is noted by the researchers who discuss it in regards to health checks.

The study suggested that routine health checks are normally conducted annually. Whereas multiple veterinary visits within a single year may sometimes indicate a health problem. The study was interested in those dogs who saw veterinarians more than once in the previous year. 

This is an unusual end point to choose

Fewer vet visits may indicate any of:

  • Better pet health
  • Worse pet health due to less preventative care 
  • An owner who doesn’t recognise signs of ill health in their pet
  • An owner who chooses to avoid conventional veterinary care and self-treat or use complementary or alternative practitioners.

There was a difference between raw meat fed dogs and conventionally fed dogs too. However, the apparent difference of raw meat diets in this respect, appears to have been heavily influenced by a large increase in the proportion of dogs who did not see a veterinarian at all in the last year, compared to the other two dietary groups. Overall, raw fed dogs were less likely to see a vet AT ALL than the other groups. This does not always equate to the animals being healthier. Owners feeding raw meat diets also had lower neutering rates. This may relate to the reduced likelihood of them visiting veterinarians. Furthermore such owners may be less likely to receive, or to comply with, veterinary advice, and routine preventative healthcare advice.

 The research notes state that

‘there is reason to believe that guardians of dogs fed raw meat are less likely to visit veterinarians, for reasons not directly related to the health of their animals. It is known that those who feed a raw meat diet are less likely to seek advice from their veterinarian, and more inclined to gather information from other sources, such as online resources which vary greatly in their reliability. The perceived opposition of most veterinarians to the feeding philosophy and choices of guardians feeding raw meat diets, may make these people less trusting of veterinary advice, and less likely to visit veterinarians, in general. This is likely to have altered this apparent general health indicator, for reasons unrelated to the health of these dogs.’

Inconsistent analysis of the data

Unfortunately, the researchers fail to note that this phenomenon may also be seen in the vegan feeding group; who also had a higher percentage than conventional meat group for not seeing a vet at all and could also be down to similar ideologies seen in the raw feeding group.

For example, in the vegan group there was an increased risks of internal parasites in dogs. The vegan lifestyle adhered to by such guardians commonly involves a commitment to minimising harm to living creatures. It is possible some vegan guardians consider internal parasites to be living creatures deserving of consideration, reducing their use of anthelmintics (de-wormers). Or perhaps suggests that they are conscious of the possible effect of parasite treatment on the environment. This is a possible example of where owner ideologies can filter down to the health of their pets.

The authors go to great lengths to explain away the better “health” (fewer vet visits) of the raw-fed dogs compared to the conventionally-fed ones. But then state on rather weak grounds that the same arguments do not somehow apply to the vegan-fed ones.

Personal Bias of Respondents

Personal bias can also sway results when obtaining survey results. We already know that when surveys are distributed, we often experience a bias; where people interested in that particular topic are more likely to respond as they are passionate about the subject. This means that personal bias of respondents can lead to bias within results, as we do not have a representative sample. To have personal biases is to be human but that does not help to make robust scientific conclusions. We all hold our own subjective world views. And we are influenced and shaped by our experiences, beliefs, values, education, family, friends, peers and others. That is true of us and of the researchers as much as anyone else. Given that the response pattern is so different from the general population, it does suggest a skewed population.

Dog diet is actually a very emotive topic and can be a source of much angst. As such those with a particular passion or interest in their dog’s nutrition may have been more likely to respond.

Unconscious Bias

Another source of potential bias when relying on a respondent’s answers, is unconscious bias. This could occur if a guardian using a conventional or unconventional pet diet expected a better health outcome as a result. And if this expectation exerted an unconscious effect on their answers about pet health indicators. 

Caregiver placebo is also an unconscious issue that is seen in owners. The caregiver placebo essentially means that, as the owners have faith in a treatment, they see a notable benefit in their pets, even if the animal is not clinically any better. It can be as prevalent as 39.7% in owners – this effect works in combination with a number of other factors. It is conceivable that vegans, raw-feeders, or respondents following other dietary groups. Such as omnivores might have had greater subconscious expectations of good health when animals were fed diets similar to their own.

When guardians were asked for their own assessments of their dogs’ health status there was a shift of roughly 5% in all groups, toward considering dogs to be healthier than veterinarians were expected to rate them. This suggests that owners are not objective at assessing their dog’s health status.

In many ways this is the biggest problem with the survey. It definitely shows that owners believe their dogs to be healthier if on a vegan or raw diet. It does not however show that they were healthier.

The dogs weren’t on an exclusive diet

Another limitation to the study was that these diets were usually not fed exclusively. As might occur within a controlled study in a research institute. Of the 2,536 dogs in the three main diet groups, 76% received a variety of treats at least once daily. 37% were also regularly offered dietary supplements. 

If the benefits of a raw or vegan diet, and the harms from a processed commercial diet, are so significant we would expect this to significantly muddy the waters when interpreting the results!

Dogs who had to change diet

In the survey, if a dog had to move onto a ‘therapeutic’ diet, then the dog guardians were asked to respond about the diet they were previously on. 

Interestingly, again raw fed dogs were less likely to move to a therapeutic diet. As above a number of factors could have resulted in this outcome. However, there were significant differences in likelihood of subsequent progression onto a therapeutic diet. Dogs initially fed vegan diets had more than three times the risk of this outcome (changing to a therapeutic diet), compared to those initially fed raw meat. This does raise questions as to why so many vegan fed dogs needed to be transitioned to a more expensive ‘prescription’ or clinical diet, if they were in fact healthier. This would be an interesting area to consider.

Unfortunate Timing

A very unfortunate issue was that the survey was made available from May–December 2020, during the global coronavirus (COVID-19) pandemic. 

As we know at this time UK lockdowns occurred during all or part of March, April, July, and September to December. Subsequent lockdowns may have decreased the frequency of veterinary visits in some regions, and potentially, the use of medications or therapeutic diets prescribed by veterinarians. For example, 71% of respondents stated they were from the UK and this was at the same time as lockdowns were occurring and there were also local and regional discrepancies in lockdowns and tier restrictions that could have meant certain dog owners couldn’t access face to face appointments.

While this may have impacted all three groups equally, it is not implausible that people feeding their dog a vegan diet are generally more health-conscious. And potentially less likely to visit a crowded veterinary practice in the middle of a global pandemic than other groups. If this was indeed true, it would invalidate the entire metric of “vet visits”; which is the main measure of this study. Sadly, the authors did not address this apparently obvious possibility.

Encouraging findings…

The results of this study are encouraging for the potential of a new and complete dietary choice for owners that also allows them to maintain their belief system while having the joy of dog ownership. We have no fundamental issue with the concept of vegan diets. As long as they are properly formulated and genuinely balanced; as the authors themselves agree is key to any healthy nutrition.

…but not the conclusive findings that they are claimed to be.

However, despite a lot of ongoing research in the field of vegan dog diets, and undoubtedly this paper adds to the body of evidence supporting its benefits, there is currently a lack of robust data mapping the long-term health consequences, bioavailability and potential for antinutrients when feeding a vegan diet to a large number of dogs over many years. Evidence such as the Dilated Cardiomyopathy in diets using grain-free recipes and pea and legume proteins could shed more light into the potential inadequacies of such protein sources.

At the end of the day, all this paper tells us is that compared to people feeding a conventional diet, those who feed vegan or raw diets to dogs:

  • Believe their dogs to be healthier
  • Visit the vet less often during a pandemic
  • Give fewer medications.

What the study cannot tell us is whether the dogs actually were healthier. Unfortunately, we will have to wait for more rigorous controlled trials before we can draw those conclusions. It is unfair and misleading for national news to take such a conclusion and spread it to their significant public reach without properly considering the wider implications of this message.

In the meantime, keep feeding your dog a PFMA-approved FEDIAF compliant diet, whatever the ingredients may be!

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