Plant-based vs Meat-based Diets for Cats: Which is Healthier?

It hasn’t been very long since I last wrote about vegetarian diets for pets, but a new study is out that touches on the issue, so I thought it was time for an update. 

Dodd, S. A. S. et al. (2021) ‘A cross-sectional study of owner-reported health in Canadian and American cats fed meat- and plant-based diets’, BMC Veterinary Research. BioMed Central, 17(1), p. 53. doi: 10.1186/s12917-021-02754-8.

This study specifically addresses vegetarian diets for cats, so let’s start with the conclusions from my most recent article on the subject:

Cats have been more lightly touched by domestication and artificial selection than dogs, and they are clearly still obligate carnivores.34,35 This does not mean they are healthiest when fed only raw birds and small mammals, and in fact the evidence indicates this is not the safest or healthiest diet for domestic cats.36,37 However, domestication has had limited effects on the physiology of cats, and their dietary requirements are unlikely to be effectively met by plant-only diets. The need for preformed vitamin A, taurine and other specific amino acids lacking in plant-based foods, and other specific and known dietary requirements of cats makes it unlikely that long-term feeding of vegan diets will support good health in this species.35,38

There are few studies evaluating the health effects of plant-based diets on cats. Some research on cats fed commercial vegetarian diets by their owners have found deficiencies in some nutrients in some cats, but the evidence is limited and of low quality, so no robust conclusions can be drawn.9,39–41

This new study appears to suggest that the jury is in and that plant-based food for cats has no health risks and may even have health benefits. Here are some of the key results:

* No differences in reported lifespan were detected between diet types. 

* Fewer cats fed plant-based diets reported to have gastrointestinal and hepatic disorders. 

* Cats fed plant-based diets were reported to have more ideal body condition scores than cats fed a meat-based diet.

* More owners of cats fed plant-based diets reported their cat to be in very good health. 

However, even the authors recognize that these findings don’t just the general conclusion that vegetarian diets are safe or health for cats. Here is their more measured assessment:

Cat owner perception of the health and wellness of cats does not appear to be adversely affected by being fed a plant-based diet. Contrary to expectations, owners perceived no body system or disorder to be at particular risk when feeding a plant-based diet to cats. This study collected information from cat owners and is subject to bias, as well as methodological limitations. Further research is warranted to determine if these results are replicable in a prospective investigation.

The key point here is that this study didn’t actually evaluate the effect of plant-based vs. meat-based diets on health or longevity in cats. What the study evaluated was the perceptions of owners about their cats’ diet and health. The difference is crucial. 

The study was essentially an online survey distributed through a pet store and cat-centered social media. The owners surveyed were those who voluntarily chose to go to the web site and fill out the survey. This already introduces a selection bias since the people willing and able to do this differ in various ways from the rest of the population. People who respond to web surveys, for example, are younger, whiter, and richer, than people who are more likely to respond to mail or phone surveys. And people tend to respond to surveys when they have a higher level of interest in the subject than the average person. Surveys touching on unconventional diet and medical beliefs tend to be biased towards people with the strongest feelings on these issues, which biases the results.

The other major problem with such a sample is that the health status of the cats was determined entirely based on the opinions and reports of owners. No medical evaluation or records were involved. Owners, however, are neither medical professionals nor objective about their cats’ health, and they are likely to report their beliefs, which often doesn’t line up with the reality. 

For example, 55% of cats in the study were reported to be a health weight. However, previous research has shown that owner assessment of body condition is inaccurate and tends to underestimate weight in overweight cats. People who fed a plant-based diets were much more likely to report that their cats were a healthy weight (71% compared with 54% of those on meat-based diets) and less likely to report they were overweight (22% compared with 34% of those on meat-based diets). Proponents of plant-based diets will likely conclude that this means such diets lead to a healthier weight than meat-based diets. This is possible, but it isn’t a conclusion we can reach based on this survey. All we can say is that owners who choose to feed a plant-based diet believe their cats are a healthier weight than owners who feed meat-based diets. Since plant-based diets are fed to a small minority of cats (only 18% in this survey, which likely overestimated the true popularity), the people who feed these diets must choose to do so based on pre-existing beliefs about their health value. Such individuals already believe these diets are healthier, and they are likely to see and report what is consistent with these beliefs, whether or not it is the reality of their cats’ condition.

The same sorts of biases create a problem for all of the other measures of health assessed in this study. Again, it didn’t really evaluate diet and health, only diet and owner beliefs about health. As the authors suggest, prospective, blinded, randomized feeding studies would be needed to allow any strong conclusions about whether or not plant-based diets are safe and healthy for cats.

9. Knight A, Leitsberger M, Knight A, Leitsberger M. Vegetarian versus Meat-Based Diets for Companion Animals. Animals. 2016;6(9):57. doi:10.3390/ani6090057

34.     MacDonald ML, Rogers QR, Morris JG. Nutrition of the Domestic Cat, a Mammalian Carnivore. Annu Rev Nutr. 1984;4(1):521-562. doi:10.1146/

35.      Morris JG. Idiosyncratic nutrient requirements of cats appear to be diet-induced evolutionary adaptations. Nutr Res Rev. 2002;15(01):153. doi:10.1079/NRR200238

36.      Glasgow A, Caver N, Marks S, Pedersen N. Role of Diet in the Health of the Feline Intestinal Tract and in Inflammatory Bowel Disease.; 2002. Accessed December 28, 2018.

37.      Schlesinger DP, Joffe DJ. Raw food diets in companion animals: a critical review. Can Vet J = La Rev Vet Can. 2011;52(1):50-54. Accessed October 27, 2018.

38.      Weeth L, Chandler M. Vegetarian Diets. Clin Br. 2015;(January):61-63. Accessed April 29, 2019.

39.      Leon A, Bain SA, Levick WR. Hypokalaemic episodic polymyopathy in cats fed a vegetarian diet. Aust Vet J. 1992;69(10):249-254. Accessed April 29, 2019.

40.      Wakefield L, Michel KE. Taurine And Cobalamin Status of Cats Fed Vegetarian Diets. J Anim Physiol Anim Nutr (Berl). 2005;89(11-12):427-428. doi:10.1111/j.1439-0396.2005.00611_2.x

41.      Gray CM, Sellon RK, Freeman LM. Nutritional adequacy of two vegan diets for cats. J Am Vet Med Assoc. 2004;225(11):1670-1675. Accessed April 29, 2019.

Posted in Nutrition | 12 Comments

Diet-Associated Dilated Cardiomyopathy (DCM) in Dogs: What Do We Know So Far?

I have been following the controversy, and the research, on diet-associated dilated cardiomyopathy (DCM) in dogs since the issue was first addressed by the FDA in 2018. I recently had a chance to talk with Andy Roark on his Cone of Shame podcast about the subject, and I will share that when it is available. In the meantime, I wanted to post an update on the subject and also collect all of my reporting and the main sources of evidence in one place. 

This is a complex subject, and a great example of the scientific process. An observation (an apparent increase in the number of dogs not usually vulnerable to DCM developing the disease while eating grain-free or other non-traditional diets) led to a hypothesis (some component of these diets was causing DCM in these dogs). Clinicians and researchers and members of the pet food industry have all weighed in on the subject with a variety of perspectives and interpretations of the facts. The evidence is still limited, and no definitive, science-based conclusion has emerged. 

While the evidence is developed, we are able to watch not only the scientific process in action but also the influence of ego, personal bias, financial bias, and other human factors that so often influence how we approach understanding new ideas and problems in medicine. This can shed light on both the strengths and weaknesses of veterinary research and medicine.

Just to start with clarity, I will give you the bottom line as I see it:

Bottom Line

  1. Some dogs of breeds not known to be genetically prone to DCM have developed this disease.
  2. Many of these dogs have been eating diets that are grain-free or that contain pulses and legumes (e.g. peas, lentils, etc.).
  3. Many of these dogs have experienced partial or complete recovery with diet change, supplementation of taurine of other nutrients, and a variety of common treatments for heart disease. This is encouraging since genetic DCM is usually not very responsive to treatment and is typically fatal.
  4. There is uncertainty and disagreement about key facts, including
    1. Whether or not the incidence of DCM is increasing
    2. Whether or not more dogs of breeds not usually prone to DCM are getting the disease
    3. If diet is truly the main cause of DCM in these dogs
    4. What features of diets associated with DCM may be responsible for the disease 
    5. What the role of taurine is in diet-associated DCM
    6. How diet and genetics and other unidentified factors may interact to produce DCM
  5. No one on either “side” of the debate believes we have sufficient evidence to definitively answer these questions, and more research is ongoing
  6. The process of understanding this complex issue will take years and will likely lead to an understanding more nuanced and complicated than the simplest versions of current theories
  7. Economic interests significantly complicate the scientific process of understanding any relationship between diet and DCM. Because the concerns and potential changes in diet they might suggest entail an economic cost to some individuals and companies, this increases concerns about confirmation bias and funding bias in all of the debates and research around this subject.

What Should Dog Owners Do?
While there is still significant uncertainty, it is reasonable to be concerned that diets which are grain-free or contain legumes in the top 5-10 ingredients may put some dogs at greater risk of developing DCM. There are no proven health benefits to these diets, so even with uncertainty about the level of risks, it is not unreasonable to consider avoiding these diets, especially if you have a dog of a breed reported as experiencing diet-associated DCM (e.g. golden retrievers, Irish wolfhounds, American Cocker spaniels, Newfoundlands, St. Bernards). This may turn out to be an unnecessary precaution, but the limited evidence suggests potential risks may be greater than hypothesized benefits.

If you are feeding a diet with no grains or with legumes or a diet that has been listed by the FDA as potentially associated with DCM, it is reasonable to have your dog screened for DCM and taurine deficiency by your veterinarian.

If you have a dog with DCM, regardless of breed, it is reasonable to consider changing to a diet containing grains and supplementing taurine along with any other treatments recommended by your veterinarian. There is some evidence that these actions may improve the chances or survival and even recovery in some dogs.

My Posts and Articles on Diet-associated DCM

Grain-free Diets and Heart Disease in Dogs
August, 2018

FDA Webinar Discussing Dietary Risk Factors for Dilated Cardiomyopathy
September, 2018

Evidence Update: Grain-free and other “BEG” Diets Associated with Heart Disease in Dogs
December, 2018

FDA Update on Grain-free Diets and Heart Disease in Dogs
June, 2019

Column in VPN about Diet-associated DCM and the McCauley et al. Review
September, 2020

The Latest on Dietary Risk Factors for Dilated Cardiomyopathy (DCM) & Misleading Media Spin by Grain-free Diet Manufacturers
November, 2020

Other Relevant Publications

Early 2000s to 2017
Grain-free diets began to grow in popularity due to claims they might reduce food allergies (which are still unproven) and in response to “gluten-phobia” and other cultural factors. These diets went from uncommon to a large share of the dog food market.

FDA Announcement 2018
The FDA had received a steady trickle of reports of DCM in dogs for some time (~1-2/year, total of 13 from 2014-2017). Then the saw a spike in reports in the first half of 2018 (16 cases). Most of these dogs (>/= 90%) were eating grain-free diets. This led to a public announcement in July, 2018 letting veterinarians and pet owners know about the case reports and encouraging awareness and reporting of the disease. This led, naturally, to an increase in reports. Some have argued that this introduced a sampling bias and that the reason there are more reported cases is not because there truly are more cases but because there is more awareness and concern about the issue. There is likely some truth to this, however it is important to remember that the spike in reports predated the FDAs first public announcement, and that the only way we ever find out about relatively uncommon diseases is through encouraging surveillance and reporting.

The FDA made additional announcements in February, 2019 and June, 2019. These were both followed by an increase in reports, but reports did continue between announcements. The FDA also has indicated that reports of DCM in dogs are down significantly in 2020, but that reports of all conditions have decreased due to the COVID pandemic.

Kaplan et al., December 2018
Kaplan JL, Stern JA, Fascetti AJ, Larsen JA, Skolnik H, et al. (2018) Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets. PLOS ONE 13(12): e0209112. 

This study evaluated 24 Golden retrievers with DCM to investigate possible dietary causes and the role of taurine. 11 of these dogs were in congestive heart failure. Many of these dogs were eating grain-free diets or diets containing legumes, and 15/24 were eating ACANA, one of the brands later identified by the FDA as common to many of the cases. These dogs appeared to have low taurine levels compared with healthy golden retrievers, but “normal” taurine levels, in general and for specific breeds, have not been clearly established. There was a correlation between the ACANA diet and taurine level, but no correlation with the other diets. 22/23 dogs were eating lower calorie levels than predicted for their body size, which has fed some theories that one element of the problem may be relative deficiency in protein or taurine precursors in individual dogs who tend to eat less than typical dogs their size.

All dogs were treated with standard therapies for heart disease as well as taurine supplementation. Some also received other supplements (e.g. l-carnitine), and 21/24 changed diets. Of these 7 changed to diets containing grains, 4 to different grain-free diets. Almost all the dogs improved, and of those in congestive heart failure, 5/11 were able to discontinue their diuretic therapy completely, and 4 were able to reduce the dose of this medicine. Only one dog failed to improve.

This study supports the hypothesis that in golden retrievers diet-associated taurine deficiency can lead to DCM which can be improved or even cured with diet change and medical therapy. However, the small number of dogs and the great variation in their management and nutrition is a weakness of the study, and it is not conclusive. Nor does this study say much about DCM in other breeds or in dogs who are not taurine deficient.

Adin et al 2018
Darcy Adin, Teresa C. De Francesco, Bruce Keene, Sandra Tou, Kathryn Meurs, Clarke Atkins, Brent Aona, Kari Kurtz, Lara Barron, Korinn Saker. Echocardiographic phenotype of canine dilated cardiomyopathy differs based on diet type.J Vet Cardiol. 2019;21:1-9.

Though published in 2019, this study was reported at the ACVIM Forum in 2018 and was referred to in some of the early papers discussing diet-associated DCM. It was a retrospective study of dogs with DCM and a known diet history seen between 2015 and 2018. The main finding was that dogs on grain-free diets tended to have more severe changes in their hearts on ultrasound than dogs on diets containing grains. Most of these dogs did not have taurine deficiency. 7/48 dogs improved with diet change (6 of these also got taurine supplementation).

This study doesn’t address a number of the key issues in the controversy, but it does show that taurine deficiency is not the only mechanism by which diet might be causing DCM and that breeds other than golden retrievers are affected.

Freeman et al Dec., 2018
Freeman LM, Stern JA, Fries R, Adin DB, Rush JE. Diet-associated dilated cardiomyopathy in dogs: what do we know? J Am Vet Med Assoc. 2018 Dec 1;253(11):1390-1394. doi: 10.2460/javma.253.11.1390.

This was a commentary summarizing the research findings and hypotheses to that point. The authors reported a subjective impression among cardiologists they surveyed that DCM was being seen more often and more commonly in breeds not previously known to be susceptible to it. Many of these dogs were on nontraditional diets, including diets that were grain free, that contained legumes/pulses, that had unusual protein sources, or that were made be relatively new and small companies. These were called BEG diets as a shorthand (boutique manufacturers, exotic protein, grain free). This acronym has generated a great deal of rancor in the pet food industry. 

The authors were explicit about the fact that there was insufficient data to show these observations were even correct, much less that there was a causal relationship between specific aspects of BEG diets and DCM. The paper was intended to start, not finish, a conversation and research effort to understand the initial observations and hypotheses.

FDA Feb 2019 Announcement
At this point, the FDA detailed the case reports they had received. The agency indicated that 294 cases had been reported, 90% of which were being fed grain-free diets, mostly containing lentils, and that the other diets involved were often vegetarian diets.

FDA June 2019 Announcement
In this announcement, the FDA detailed the breeds and specific brands of food included in the reports the agency had received to that date. This generated a great deal of controversy from industry, especially as the market share of some brands and grain-free diets declined noticeably after the announcement. Despite the uncertainties about the causal role of diet in DCM, the fact that certain brands predominate in these reports is a legitimate piece of data and cause for concern. While the FDA has tried to be very politic about not blaming specific manufacturers or products or ingredients for diet-associated DCM, it is obliged to make this information available so that appropriate investigations can be carried out.

Similarly, the overrepresentation of relatively rare protein sources, such as kangaroo, in the diets associated with these cases raises a legitimate question about the potential role of such proteins in this disease. The amino acid profile and bioavailability of uncommon protein sources is not as well-characterized as those of common proteins such as beef, chicken, and pork, and until this research is done, it is reasonable to ask whether such sources might have relevant deficiencies. More recent reporting by the FDA, though, has not found consistent associations between protein source and DCM, even as the association between legumes and grain-free diets has remained strong.

McCauley et al 2020
McCauley SR, Clark SD, Quest BW, Streeter RM, Oxford EM. Review of canine dilated cardiomyopathy in the wake of diet-associated concerns. J Anim Sci. 2020;98(6).

This is a comprehensive narrative review of DCM and various known and potential causes. I have written about this paper in detail elsewhere. It is a useful contribution to the discussion, and it makes several important points about the limitations of existing research evidence:

  • the studies include few subjects
  • there is variable representation of breeds with different genetic predispositions to DCM 
  • diet and health histories are often incomplete

These limitations preclude any definitive conclusion regarding a causal relationship between BEG diets and DCM. In emphasizing that additional research is needed to clarify the role of diet in DCM, the review authors agree with the authors of the papers proposing the hypothesis.

However, the authors of this review also chose not to address other information relevant to evaluating the hypothesis, including:

  • patients with DCM from breeds not previously thought to be predisposed to the disease are disproportionately represented among cases fed BEG diets
  • a large proportion of diets associated with DCM cases were produced by small manufacturers or contained uncommon protein sources even though such diets are a small fraction of those on the market

The authors make several strong statements that go beyond a factual critique of the existing evidence:

The use of the acronym BEG and its association w/ DCM are without merit because there is no definitive evidence in the literature.

This exhaustive review of the literature provides support that eliminates the pet food characteristics that have been implicated to have a subjective association with DCM.

Unfortunately, the arguments made in this paper are undercut by the failure of the authors to disclose up front that several of them are employed by companies producing grain-free diets or by BSM, a nutrition consulting firm that does business with such companies. Since the publication of this review, BSM has accepted a grant from a pulse manufacturer and active opponent of the BEG diet hypothesis to study the issue.

These conflicts of interest do not necessarily invalidate the authors’ points, but they do remind us that financial bias is a relevant concern in debates about scientific issues, especially when the evidence is preliminary and uncertain. 

Ontiveros et al May, 2020
Ontiveros ES, Whelchel BD, Yu J, et al. Development of plasma and whole blood taurine reference ranges and identification of dietary features associated with taurine deficiency and dilated cardiomyopathy in golden retrievers: A prospective, observational study. Staffieri F, ed. PLoS One. 2020;15(5):e0233206. doi:10.1371/journal.pone.0233206

This study evaluated taurine levels in 86 golden retrievers eating traditional dry dog foods (contains grains, no legumes other than soy and no potatoes in the top 5 ingredients, manufactured by a large company) or nontraditional diets (kibble or raw diet with no grains, legumes or potatoes, or made by a small company). 

Taurine levels were found to be lower in dogs on the nontraditional diets. These dogs were also more likely to have ultrasound findings suggestive of DCM. A number of methodological concerns and potential conflicts of interest have been raised about the study, some acknowledged and others disputed by the authors.

KSU Virtual Conference, Sept. 2020
The FDA organized a virtual conference on the subject of diet-associated DCM through Kansas State University. Many of the presentations are available there, though not all. 

The FDA provided updated statistics on the case reports received (1100 canine cases as of July, 2020 from all 50 states and Canada) and preliminary data on a sibset of cases analyzed by theVeterinary Laboratory & Investigation Response Network (Vet-LIRN). 

 Of 150 cases reported between 1/2018 to 4/2019, 107/121 recovered fully or partially. All of the dogs who recovered fully had changed diets, and many had received taurine, pimobendan, and other treatments. Full recovery took 7-13 months.

Consistent with previous reports, 90% or more of the diets fed before the DCM diagnosis were grain free and had legumes high in the ingredient list. The protein sources in the diets fed to these cases were varied, and no consistent association was seen.

Representatives from BSM also made several presentations at the symposium supporting several claims:

  • There is no actual increase in DCM associated with increasing popularity of grain-free diets
  • There is no change in the breeds being diagnosed with DCM, and most are still breeds with known genetic predispositions
  • Only fasted plasma taurine levels have been shown to correlate with taurine level sin heart muscle, so the methods used to measure  taurine in other studies may not be reliable
  • There is no evidence that small pet food manufacturers have lesser quality control than larger companies or are disproportionately represented among cases of DCM reported to the FDA

Data from a survey of cardiology practices that was presented by BSM at the conference was subsequently published as a preprint for a journal article still undergoing peer review:

Quest B, Clark SD, Garimella S, Konie A, Leach SB, Oxford EM. Incidence of canine dilated cardiomyopathy, breed and age distributions, and grain-free diet sales in the United States from 2000-2019: A retrospective survey. bioRxiv. September 2020:2020.09.27.315770. doi:10.1101/2020.09.27.315770

Pezzali et al, January, 2020
Pezzali JG, Acuff HL, Henry W, Alexander C, Swanson KS, Aldrich CG. Effects of different carbohydrate sources on taurine status in healthy Beagle dogs. J Anim Sci. 2020;98(2). doi:10.1093/jas/skaa010

In this lab study, 12 Beagles were fed diets with grains or diets without grains and utilizing potatoes, peas, or tapioca starch as a carbohydrate source. Taurine levels did not differ between the groups. The relevance of this for other breeds, other diets, and DCM in dogs without taurine deficiency are unclear.

Donadelli et al, July, 2020
Donadelli RA, Pezzali JG, Oba PM, et al. A commercial grain-free diet does not decrease plasma amino acids and taurine status but increases bile acid excretion when fed to Labrador RetrieversTransl Anim Sci. 2020;4(3). doi:10.1093/tas/txaa141

In this lab study, 8 Labrador retrievers were fed an ACANA grain-free diet for 26 weeks and their taurine levels were measured. No decline in taurine was seen. The relevance of this for other breeds, other diets, and DCM in dogs without taurine deficiency are unclear.

Freid Nov 2020
Freid KJ, Freeman LM, Rush JE, et al. Retrospective study of dilated cardiomyopathy in dogs. J Vet Intern Med. December 2020.

This study looked at medical records of dogs diagnosed with DCM at the Tufts Veterinary School between 2014 and 2018. Data from 71 dogs were analyzed, and 56/72 were eating nontraditional diets (grain-free, containing pulses, or manufactured by a company not meeting international industry standards). Dogs in the two diet categories were similar in most ways, though dogs on nontraditional diets were more likely to be in congestive heart failure when diagnosed. Taurine was only measured in a few dogs, most in the nontraditional diet group, and was only low in a couple of them. The study also reported an increase in the number of DCM cases seen at the hospital, and this began in 2016, before the first FDA announcement about diet-associated DCM in 2018.

Dogs were treated with a variety of different medications for their heart disease. Some received taurine supplementation (almost all in the nontraditional diet group), and about 55% in the nontraditional diet group had their diet changed while only 49% of those in the other group changed foods. Dogs eating a nontraditional diet that had a diet change lived significantly longer than dogs who did not. The authors concluded:

The underlying cause of diet-associated DCM remains unknown but is being actively investigated by the FDA and several researchers. Diet-associated deficiencies, toxins, or a multifactorial etiology (eg, nutritional, other environmental factors, genetics) remains possible explanations. The underlying cause of diet-associated DCM remains unknown but is being actively investigated by the FDA and several researchers. Diet-associated deficiencies, toxins, or a multifactorial etiology (eg, nutritional, other environmental factors, genetics) remains possible explanations. The underlying cause of diet-associated DCM remains unknown but is being actively investigated by the FDA and several researchers.


Posted in Nutrition | 3 Comments

Raw Pet Foods & The Death of Expertise

One of the more enlightening, and terrifying, books to come out in the last 5 years is Tom Nichols’ The Death of Expertise. In clear prose, with cogent argument and substantiating evidence, the author makes the case that the proliferation of misconceptions, delusions, and bizarrely wrong beliefs about the world in every domain, from science to politics, reflects powerful and pervasive elements of American culture. Access to accurate information is easier than ever, yet misinformation thrives. The problem is not that the truth isn’t available to us, it’s that we actively reject it. In Nichols’ words,

These are dangerous times. Never have so many people had so much access to so much knowledge and yet have been so resistant to learning anything.

[The real problem is] we’re proud of not knowing things. Americans have reached a point where ignorance, especially of anything related to public policy, is an actual virtue. To reject the advice of experts is to assert autonomy, a way for Americans to insulate their increasingly fragile egos from ever being told they’re wrong about anything…It is a new Declaration of Independence: No longer do we hold these truths to be self-evident, we hold all truths to be self-evident, even the ones that aren’t true. All things are knowable and every opinion on any subject is as good as any other.

This is a phenomenon I have wrestled with for many years in my efforts to promote science-based veterinary medicine. Giving people facts and evidence is not sufficient because, as Nichols says, “When feelings matter more than rationality or facts, education is a doomed enterprise.” Believers and promoters of pseudoscience in medicine are armored by feelings and conviction against any inconvenient facts or evidence. And the average pet owner is at a disadvantage since they can’t always judge the relative merits of scientific claims or data for themselves, and they are left deciding which source of information to trust or, in the worst case, simply choosing to believe the claim that best fits their pre-existing world view.

A recent survey of pet owners investigating attitudes about raw and commercial coked pet diets illustrates this death of expertise quite starkly. 

Empert-Gallegos A, Hill S, Yam PS. Insights into dog owner perspectives on risks, benefits, and nutritional value of raw diets compared to commercial cooked dietsPeerJ. 2020;8:e10383. doi:10.7717/peerj.10383

The facts are clear and not seriously questioned by actual experts, including veterinary nutritionists and most mainstream veterinarians. Raw diets have no proven benefits and any claimed for them are based on pure anecdote or theory. Raw diets do, however, have clearly established risks, including causing potentially deadly food-borne illness and often being nutritionally inadequate. The evidence to support these facts can be found in the many posts I have written on this subject.

Unfortunately, these facts are inconvenient for people who choose to feed such diets, and their reaction to being confronted with them is simply to redefine themselves as the “real experts.” Among owners feeding conventional cooked diets, 78% felt their veterinarian had a high level of knowledge about nutrition (4 or 5 on a 5-point scale). In this age when anyone can declare themselves an expert based on an internet search or some other informal way of investigating a subject, 65% of owners feeding cooked diets rated themselves as highly knowledgeable about pet nutrition, at the same level of knowledge, in fact, as their veterinarian. It is pretty unlikely that a majority of these owners have degrees in animal health or have taken formal instruction in animal nutrition, so this is a pretty unreasonable assessment. But it gets worse.

Of the raw feeders, 86% declared themselves highly knowledgeable (4-5 out of 5) while only 45% of them credited their veterinarian with this level of expertise. Raw feeders are no more likely than other pet owners to have degrees in animal health or nutrition, but they do have stronger feelings about the subject and are more likely to have investigated web sites or books for the general public making nutrition claims. These owners, whose beliefs are the least consistent with the facts, have the greatest confidence in their own knowledge and the least confidence in the expertise of actual veterinary professionals. This is unlikely to lead to good feeding choices or the best outcomes for pets.

The irrationality behind this false sense of expertise is illustrated by other findings in this study. Raw feeders rated commercial and homemade raw diets as more nutritious and safer than commercial cooked diets, both beliefs inconsistent with the facts. These owners likely imagine they have some special knowledge or insight into the “real truth” about pet food that owners feeding cooked diets, or even veterinarians, lack. This insight was not evidence, however, in their free-text answers to questions about the reasons for feeding raw diets, which included many vague references to unproven health benefits and terms consistent with unscientific beliefs about nutrition, such as “natural,” “processed,” “chemicals” and so on. 

These owners clearly believe strongly that raw diets are healthier than cooked diets, but the strength of this belief, and the confidence in their own expertise in the subject, are based on misinformation and falsehoods. As Mulder would say, “The Truth is Out There,” along with the evidence to support it. But truth and facts aren’t nearly as effective at generating belief as the vapid handwaving and passionate proselytizing of raw food advocates. Ultimately, if people choose belief and feelings over science and expertise, they can maintain any belief regardless of the facts. Raw feeding, like so many other alternative veterinary practices, is just one more illustration of this pervasive and malignant cultural problem.

Posted in Nutrition | 11 Comments

Neutering and Aggression in Dogs

I have written extensively about the positive and negative effects of neutering dogs for many years. This is an area of great controversy and rapidly advancing research. There is no simple relationship between neutering or age at neutering and health. Neutering itself changes many aspects of an animal’s physiology, and some of these changes have beneficial effects while others have harmful effects. The breed and genetic makeup of an animal, the age at which it is neutered, the environment in which it lives, and many other factors all work together to influence health, and the simplistic notion that neutering is “good” or “bad” for all dogs is simply untrue.

I recently found an interesting study examining the relationship between neutering and aggressive behavior in dogs which illustrates this complexity.

Farhoody P, Mallawaarachchi I, Tarwater PM, Serpell JA, Duffy DL, Zink C. Aggression toward Familiar People, Strangers, and Conspecifics in Gonadectomized and Intact DogsFront Vet Sci. 2018;5:18. 

It has traditionally been assumed, by dog owners and many veterinarians, that neutering reduces aggression, at least in males. The research to date, however, has been far from clear. Some studies support this idea, others show no effect of neutering on aggressive behavior, and some find neutering can increase aggression. The sex of the dog and the age at which it is neutered all play a role as well. While there likely is some relationship between neuter status and behavior, including aggression, behavior is a tremendously complex product of a multitude of factors, and what relationships there is between this and neutering is unlikely to be simple or universal.

This study approached the question in an interesting way. By looking through data collected in the past on thousands of animals using a behavioral questionnaire that has been widely used and is well-validated, they selected a huge population of dogs for which the details of neutering and also of aggressive behavior patterns were known. This has the advantage of a large enough s ample size to allow robust statistical comparisons. However, such a retrospective design has a lot of limitations, including the inability to acquire and consider relevant information that might not have been recorded in the survey and potential bias in the population of animals included. This was not a study population selected in an unbiased fashion specifically for the project but a database of voluntary responses to an online behavior questionnaire. People likely to fill out such a questionnaire, and their dogs, are likely different in meaningful ways from people not choosing to do so.

The researchers used mathematical techniques to compare the rates of different types of aggressive behavior (directed towards familiar people, directed towards unfamiliar people, and directed towards other dogs) with information about neutering and other factors (sex, age, weight, etc.). When all of the variables considered in the study were included in the model, no relationship was found between neutering at any age and any type of aggression.

When a different model was used to consider only a limited subset of the variables considered, the only relationship found was a small increase in the odds of aggression towards strangers among dogs neutered between 7 and 12 months of age.

The real-world significance of these findings is not completely clear. The authors emphasize that the results don’t support the assumption that neutering reduces aggression since neutered dogs were not significantly less aggressive than intact dogs. Of course, the other way to frame the findings is that the results suggest neutering has no effect on aggression either way, so aggressive behavior shouldn’t be a major consideration in decisions about neutering. The finding that aggression towards strangers was more common in dogs neutered between 7 and 12 months of age is likely a statistical fluke, and though the authors propose some possible hypotheses for it, they admit it is difficult to explain.

The study did not consider breed, which likely plays a significant role in some kinds of aggression based on previous studies. It also did not consider owner factors, which clearly influence both the behavior and the neuter status of dogs. It has always been an open question whether aggression by certain breeds or by intact dogs might have more to do with the owners who choose the breed and decide whether or not to neuter than with the neutering or breed per se. This study does not help clarify that question.

Overall, this is an interesting but not definitive contribution to the subject of how neutering might affect behavior. It undermines the traditional and simplistic notion that neutering prevents aggression, and it suggests that there are many factors influencing aggressive behavior in dogs and neutering is only one and likely not the most important.

Posted in General | 3 Comments

Five Most Dangerous Alternative Therapies for Pets- From SkeptVet TV

Posted in SkeptVet TV | 7 Comments

New Study Shows No Benefit from Acupuncture for Dogs with Arthritis

I have written extensively over the years about acupuncture, and my investigations have ranged from the laboratory animal and human literature to veterinary clinical studies, to completing a certification in medical acupuncture and treating patients in my clinic. Through all of this, I have found little to change my basic views of acupuncture, summarized in my latest article on the subject:

Most acupuncture treatment is still based on unscientific religious and philosophical principles. Despite extensive research over many decades, plausible scientific explanations for how traditional acupuncture might work have not been clearly validated. Clinical studies in humans have failed to find clear evidence of meaningful benefits for most conditions compared with sham interventions. 

There is little high-quality clinical research on veterinary acupuncture, and the widespread belief that it is an effective therapy is based mostly on anecdote and low-quality evidence. Better research evidence has been challenging to generate due both to the difficulty in creating an effective placebo comparator for acupuncture and to the impact of entrenched bias and unscientific beliefs among acupuncturists evaluating the practice.

Put more succinctly, the principles are either unscientific or unproven, it probably has little if any benefit, and it is relatively low-risk if applied sensibly and note used in place of science-based medicine. A recent clinical study in dogs with arthritis serves as additional support for these views.

Baker-Meuten A, Wendland T, Shamir SK, Hess AM, Duerr FM. Evaluation of acupuncture for the treatment of pain associated with naturally-occurring osteoarthritis in dogs: a prospective, randomized, placebo-controlled, blinded clinical trial. BMC Vet Res. 2020;16. doi:10.1186/S12917-020-02567-1

This was a nicely done study illustrating the use of some methods for objectively evaluating acupuncture in veterinary patients. Like most veterinary studies, it was small, with only 36 dogs (4 of which did not complete the study). The design was a crossover study, meaning all patients got both acupuncture and placebo treatment and were randomly assigned to get one or the other first with a washout period between treatments. This is a good way to minimize the errors that can be creep into the data if dogs with different characteristics get different treatments. For example, if the dogs in the placebo group had much worse arthritis than the dogs in the acupuncture group, it could easily look like the treatment was working even when it wasn’t.

There was also an effort at blinding, meaning the owners weren’t supposed to know when their dogs got placebo treatment and when they got acupuncture. This would help reduce the tendency of people who already believe in the effectiveness of acupuncture to see improvement due to caregiver placebo effects. Unfortunately, this blinding didn’t appear entirely successful. About 58% of owners correctly guessed when their dogs were getting acupuncture or placebo and only 19% guessed incorrectly (the rest said they couldn’t tell). While assessing the success of blinding is a good idea, a well-blinded study should have roughly equal numbers of people guessing real and placebo treatment. The veterinary staff and investigators were not blinded, which is unfortunate since this can not only bias the assessment of whether the treatment works but also subtly influence the perceptions of the owners, which may have been the case in this study.

The investigators used both subjective measures of effect, by both owners and veterinarians, and also objective measures, activity monitors and a force plate that measures the amount of weight a dog with arthritis can put on a painful limb. 

The treatment was a standardized acupuncture protocol based on a survey of veterinary acupuncturists, both from the Traditional Chinese Medicine school and also from the somewhat more scientific Medical Acupuncture trainingbackground. Some will still undoubtedly complain that this invalidates the results since theoretically acupuncturists treat every patient with a unique approach based on whatever set of theories they believe in and their own clinical experience. However, there was tremendous overlap among the vets surveyed in the approaches they used, and there is no evidence to support the claim that haphazard individualization of treatment works any better than standardized protocols. 

The treatment also involved electrical stimulation through the acupuncture needles. There is some debate about whether this is really “acupuncture” or simply a form of electrical nerve stimulation dressed up in folk medicine clothes. There is slightly better evidence for potential benefits to such electroacupuncture than for needling alone (“dry needling” as it is typically called) though the evidence is still not very robust.

The placebo was not a sham acupuncture treatment, as is often used. Instead, dogs were simply taken into the room where acupuncture would normally be done and spent an equivalent amount of time interacting with one of the veterinary staff. There are pros and cons to this approach. Defining sham acupuncture is tough because it is not clear that specific acupuncture points even exist or that it matters where you insert needles. In human studies, needling at a “fake” acupuncture point often has the same effect as needling at a “real.” This probably means the responses are mostly due to placebo effects and non-specific irritation from the needle insertion rather than some magical manipulation of energy or some special quality to the points traditionally used. However, if sham needling has the same effects as real acupuncture, then it doesn’t make a very good placebo control.

A non-treatment placebo avoids this problem, and it still controls for one of the most likely causes of placebo effects in animals, which is human contact. However, insofar as needling and electrical stimulation due have biological effects (whether clinically relevant or not), this is very different from just sitting in a room with a person, so arguably the placebo control isn’t very much like the treatment, and this opens the door for error.

In any case, the study did not show any convincing evidence of any benefit from acupuncture for dogs with arthritis. Both objective measures (activity monitor and force plate) showed no difference between placebo and acupuncture, as well as no difference between the baseline period and either the placebo or the acupuncture periods. This is a pretty solid negative finding. 

The subjective assessment by the veterinarians also showed no difference between acupuncture and placebo.

Of the subjective measures by the owners, the results were mixed. The overall questionnaire asking owners about effectiveness of treatment at the end of the study showed no difference between placebo and acupuncture. Another subjective measure employed by the owners showed no difference between placebo and acupuncture but did show a difference between the baseline period and the acupuncture period. Finally, yet another subjective assessment did show some difference between both baseline and placebo and the acupuncture treatment.

Inevitably, when multiple measures are used together, some will show a difference and others won’t. Showing a convincing effect requires a consistent pattern of positive results, especially from the more objective measures. Neither of those criteria were met, and the authors acknowledged that, “We rejected our hypothesis because we were unable to detect evidence of differences in the objective outcome measures…However, some treatment response was found using owner completed CMI to assess clinical function and chronic pain. These results should be cautiously interpreted while considering the natural fluctuations in the disease process of OA as well as the caregiver placebo effect.”

Of course, the authors practice acupuncture and clearly believe it is effective, so this is a difficult conclusion to reach. I admire their integrity in acknowledging that the study results did not match h their expectations, though I suspect it is unlikely to shake their confidence in their acupuncture practices. As is often the case in research reports, the authors make some attempt to find explanations for the failure to show an effect other than the most obvious, that the treatment doesn’t work. These include acknowledging that the purported benefits from acupuncture seen in studies of people with arthritis are quite small, considerably less than those from conventional treatments such as nonsteroidal anti-inflammatory drugs, which might mean that any effect from acupuncture might have been swamped in this study by the other treatments the dogs received. This, of course, raises the question of how worthwhile acupuncture is if its effects are so small as to be difficult to see in dogs getting treatments with better supporting evidence of benefit.

The authors also acknowledged that the apparent improvement seen in some dogs from placebo treatment likely represented a caregiver placebo effect. Such effects can, of course, also make therapies like acupuncture look like they work when they don’t in real clinical practice.

Bottom Line
This study found no benefit from acupuncture treatment for dogs with arthritis over placebo (essentially no treatment). Though the methods were not perfect, overall the study was designed, conducted, and analyzed appropriately, and it represents pretty strong evidence against the value  of acupuncture for treating arthritis pain in dogs. Given the lack of strong, compelling evidence in humans despite hundreds of studies over many decades, and the lack of good evidence in other veterinary studies, the most reasonable conclusion at this point is that acupuncture probably has little to no clinical benefit for arthritic dogs. If it is used at all, it should be as an adjunct, not a primary, treatment and only with full disclosure to owners about the likelihood that it is nothing more than a placebo.

Posted in Acupuncture | 1 Comment

A Discussion of Evidence-based Arthritis Management for Dogs

I had the enjoyable experience of participating in a Facebook Live Discussion with Dr. Hannah Capon of the Canine Arthritis Management Project about evidence-based arthritis management for dogs. We talked about how to evaluate treatments for arthritis and whether or not they are working, as well as taking questions about specific treatments from viewers.

Check it out!

Posted in Presentations, Lectures, Publications & Interviews | 5 Comments

Food is Love- Veterinarians and Nutrition

Food is Love
As a child, I was a big fan of the Peanuts cartoons. One of my favorite characters was Snoopy, a suave, bipedal beagle who wrote novels and engaged in breathtaking aerial combat with his nemesis, the Red Baron. Though Snoopy was unlike most other beagles I have known, he had one characteristic common to others of his breed, and indeed most dogs. When suppertime arrived, all other activities were forgotten, and he often launched into an exuberant, joyful suppertime dance. Every feeding was a celebration for Snoopy, a celebration not only of food but of the bond between dog and owner.

Few subjects generate the same intensity of emotion in pet owners as the question of what to feed our animal companions. Feeding our pets is the quintessential act of caring and love. And based on how most dogs and cats act at feeding time, it certainly seems like a highlight of the relationship for them! 

There is also a deep sense in most pet owners that choosing a pet food has tremendous significance for the health and well-being of their pets. Everyone wants to give their pets the “best” food, the food that will keep them active and happy and prevent illness for as long as possible. We have all been told most of our lives that what we eat affects our health, so we want to make good, healthy nutritional choices for our pets as well.

The food we give our pets food is also something we have control over. We naturally want to do everything we can to ensure our pets stay healthy, but many factors that influence the risk of disease are beyond our control. Food, at least, is something tangible that we know has an influence on health, and we can make choices about what we feed our pets that give us a sense of actively influencing their health. 

The significance and emotion attached to feeding can be good in that it motivates pet owners to seek information and try to make thoughtful, informed choices about what to feed. However, the pressure to find the “right” food can also make clients vulnerable to irrational decisions, and to exaggerated or unproven claims about nutrition and health. Like most medical subjects, nutrition is complicated and full of uncertainty and nuance, and the desire to find the perfect food to guarantee our pets good health is all too easy to exploit by those selling pet food or promoting particular feeding ideologies. Even smart, rational people can get swept away by enthusiasm or diet fads that may not be based on reliable scientific principles or evidence.

The role of veterinarians in decisions about nutrition is critical. We should be a reliable and convenient resource for owners, supporting rational feeding choices. But are we? Do pet owners rely on their vets for guidance about nutrition, and do we live up to our responsibility to provide it?

Do Clients Trust Us?
Unfortunately, the idea that veterinarians are not reliable sources of nutrition information is widespread. Many voices, from the media and breeders and even some of our colleagues within the profession, are loudly proclaiming that vets know little or nothing about pet nutrition, that what we do know is mere pet food industry propaganda, and that we are more concerned with selling food than with using nutrition to support the health of our patients [see examples below]. 

In general, the public sees vets as pretty trustworthy and likeable, sometimes even more so that other healthcare professionals.1 While there is some variability among studies in the extent to which pet owners trust our advice about nutrition, most show that a majority of clients desire advice from their vet on what to feed and have high confidence in this advice.2–7  However, the full picture is more complicated. The extent to which clients use and trust veterinary advice on nutrition varies with characteristics of owners, the pets they own, and the type of diets they choose to feed.

Not surprisingly, for example, owners feeding non-traditional diets rather than commercial pet food express less confidence in veterinary nutrition advice.4,7,8 One study found that owners feeding raw animal products to their pets were much less confident in veterinary nutrition advice than those not feeding any raw foods.4 About 54% of clients who did not feed raw trusted this advice “very much” while only 13% of raw feeders had this level of confidence. 

This seemed to generalize beyond nutrition to medical advice in general. In one study, advice about topics other than nutrition was considered highly trustworthy by 64% of clients who did not feed raw products, but only 36% of those clients who did.4 Raw feeders are less likely to trust veterinary recommendations about vaccination, flea control and other preventative health interventions.4,9 This suggests that pet owners who feed unconventional diets may have a broader distrust of conventional veterinary medicine and a more favorable view of alternative medicine. 

Such a connection between unconventional nutritional practices and a general distrust of science-based veterinary medicine seems likely given the consistent criticism of vaccines, pharmaceuticals, and other science-based interventions by veterinarians advocating for raw or other unconventional diets.10–12

Even those suspicious of veterinary medicine in general and committed to feeding their pets unconventional diets, however, still have some interest in veterinary nutrition advice. In one survey, 50% of raw feeders trusted veterinary advice in general “somewhat,” and 32% had this level of confidence in the nutrition knowledge of their vet.4 Surprisingly, among cat owners, a majority reported choosing to feed raw was influenced by advice from their veterinarian (58%) or from other veterinary sources (78%).4 This suggests that the problem may not necessarily be a true lack of trust in veterinarians as a source of advice about nutrition so much as a desire to follow veterinary advice so long as it is consistent with other values or beliefs related to pet health. Owners who feed raw or other unconventional diets, for example, often hold beliefs about the health benefits of such diets that have not been scientifically validated and which are unlikely to be affirmed by most veterinarians. However, these beliefs may be supported by vets with alternative philosophies or approaches, and raw feeders are likely to trust such vets more because their views are aligned.4,7–9,13

Another factor influencing both client feeding choices and their degree of trust in veterinarians as a source of information about nutrition is attitudes towards pet food producers. Pet owners, particularly those feeding unconventional diets, often express significant distrust in the motives and claims of commercial diet manufacturers and in the health value of commercial foods.2,4,8,9

Commercial pet diets are sometimes seen as “junk food,” equivalent in nutritional and health value to human convenience and snack foods because both are “processed.” Pet owners sometimes express concerns about the health effects of grains, organic versus conventional ingredients, genetically-modified ingredients, meat from animals that are ill or have died or been euthanized, and other real or imagined components of commercial diets. There have also been some very serious incidents of real harm to pets from adulterated or contaminated commercial diets, and many pet owners are aware of these.14 Such concerns undermine confidence not only in pet food manufacturers but in veterinarians because we are seen recommending primarily commercial diets and as having potential financial and other conflicts of interest that influence these recommendations.

Should Clients Trust Us?
The arguments against heeding veterinary advice about nutrition are ultimately bad arguments which lead clients to make decisions based on misinformation, fear, marketing propaganda, and other unreliable foundations. Like many bad arguments, however, there is some core of truth to each of them that we have to address in order to protect our clients from being misled. 

What Do Vets Know about Nutrition?
The idea that veterinarians (or at least those practicing conventional science-based medicine) know nothing about nutrition is false. All veterinarians learn about the importance of nutrition and about the effect of food and feeding practices on health in veterinary school. Some of this education is in dedicated nutrition courses, but most of it is incorporated into our education about specific species and health conditions and into our hands-on clinical training. 

However, there is no denying that the quantity and quality of the nutrition education most vets receive is insufficient. Many veterinary schools do not have full-time board-certified veterinary nutritionists on faculty teaching courses in nutrition.15 Surveys of veterinarians consistently find that while we understand the importance of nutrition in health, we rarely feel confident in our training or ability to provide nutritional counseling.15–19 Apart from the small number of board-certified nutritionists, most small-animal veterinarians cannot fairly claim to be experts in pet nutrition. 

So are the critics right? I would argue they are not. While most veterinarians would like more and better training about nutrition than they have, we are still well equipped to offer pragmatic, science-based advice. We have both the general knowledge of physiology and nutrition and the ability to critically evaluate new research and incorporate it into our recommendations. This equips us to offer sound advice about nutrition to our clients.

Crucially, the alternative sources that clients turn to when they don’t trust their veterinarian’s nutrition knowledge are unquestionably less informed and less reliable. Companies marketing unconventional diets, breeders and other lay persons with little or no scientific training, and the information jungle that is the Internet cannot provide the quality or reliability of advice about nutrition that we can as veterinarians. 

Proponents of unconventional feeding practices, including many veterinarians committed to alternative medical approaches, will tell clients and conventional veterinarians that they are nutrition experts because they have “educated” themselves, above and beyond the information most veterinarians receive in school. This “education,” however, is nothing more than seeking and accepting ideas and claims that lack scientific validation but conform to the ideological biases these advocates bring to their search. 

The claim that dogs should eat a “species appropriate” diet extrapolated from what wolves or other wild canids might eat is a common example of this kind of ideologically motivated false expertise. Dogs are not wolves, and they have significant anatomic and functional differences between wolves and domestic dog. Many of these involve their systems for eating and digesting food. For all the millennia dogs have lived with humans, they have scavenged our leftovers and shared our food, and evolution has adapted them to a much more varied and less meat-centered diet than wolves or many other wild canids.20–25

Similarly, unsupported claims about the dangers of grains and carbohydrates,26–31 the benefits of raw32–35 and organic36–40 ingredients, the risks of genetically modified ingredients41–44 and various preservatives or other food additives45, and many other such ideas are frequently identified as examples of advanced knowledge or understanding that most vets lack. However, these do not constitute reliable or scientifically informed advice. Most of these claims are unsupported by good evidence, and many are clearly wrong. Even with the inadequacies in our nutrition training, we are a more reliable source of information and advice for pet owners about nutrition than the alternatives they may turn to if they lose trust in us.

Is all Our Knowledge Just Industry Propaganda
Once again, there is some legitimacy to the claim that the pet food industry has a biased perspective on pet nutrition, and that this industry has entirely too much influence on veterinary education and the veterinary profession. The giving of gifts from industry representatives has been clearly linked to prescribing behavior in physicians,46,47 and it is unlikely that veterinarians are immune to this effect. The common practice of showering students and practitioners with gifts, from coffee mugs to free food to vacations nominally intended as “continuing education,” is a real threat to both the true objectivity of veterinarians and the trust of our clients. Such practices should absolutely be discouraged.

Similarly, there is good evidence that industry funding influences the outcomes of clinical research in ways that is often in favor of the funder’s products.48,49 The concern that the scientific foundations for our recommendations about nutrition may reflect the biases of industry are not unfounded. Fortunately, the impact of such sponsorship bias on research can be mitigated with appropriate methods for controlling bias50, from trial registration and a priori publication of research protocols to strict policies banning any involvement by the funder in the design, conduct, and analysis of research studies. Ideally, more independent funding from academic institutions, non-profit organizations, and government entities would also help to reduce the influence of industry on research, though such funders have, of course, their own biases.

Once again, however, we must understand that these legitimate concerns about potential bias in the information veterinarians receive and provide concerning pet nutrition does not validate the dismissal of veterinary advice nor the acceptance of alternative information sources. We cannot simply declare all nutrition research worthless due to industry bias and make up whatever alternative theories or facts suit us. All data in science comes with limitations, and all conclusions are provisional and must be altered over time as the quality of our data improves. Such evidence is still, however, far superior to the unsubstantiated theories, intuition, and uncontrolled personal experience usually cited in support of alternative nutritional practices. 

It is also often overlooked that all scientific research incorporates biases of others kinds as well, beyond simply that of funding source, and that this influences research results as much or more than the funding source.51 Studies funded by companies producing unconventional diets or conducted by dedicated evangelists for such diets, are no less susceptible to bias than those funded by conventional pet food companies. 

Concerns raised in 2018 about potential negative health effects of grain-free and other unconventional diets52–54, for example, were recently strongly challenged in a narrative literature review.55 This review generated some controversy when the authors turned out to have financial ties to a prominent manufacturer of grain-free dog food. Conflict of interest and bias are ubiquitous and not limited to research supporting conventional or commercial diets. We must evaluate all claims and all evidence critically and be mindful of potential bias while not giving up on evidence-based medicine, which has proved its superiority to anecdote and opinion beyond question.

Veterinarians’ understanding of nutrition science and the physiology of our patients is sound The evidence for many specific nutritional interventions is quite strong;56 certainly stronger than that for the sort of claims offered by those who claim our knowledge is biased and worthless. Tens of thousands of dogs and cats thrive on conventional diets for many years, and while we will likely discover ways to significantly improve how and what we feed through future research, the notion that these diets are grossly inappropriate or harmful is nonsense. Until the alternatives to these diets can generate evidence at least as good as that for current practices, it is disingenuous to dismiss veterinary nutrition counseling on the basis of perceived industry bias.

Do Vets Care More About Selling Food than Patient Health?
I suspect no one will be surprised that my answer to this question is an emphatic “No!” Veterinarians do make money selling pet food, especially therapeutic diets intended for management of medical conditions such as chronic kidney disease, urinary tract stones, food allergies, and others. This is changing as online sales grow, and far more pet food is purchased from sources other than veterinary clinics and hospitals.57 However, food is a revenue stream just as are all the other medications, procedures, and services we provide for our patients. 

While financial incentives can influence the behavior of veterinarians and other healthcare providers, the idea that this is central motivation or that we would sacrifice patient health for profit is nonsense. Veterinarians are individuals committed to animal welfare, and there is no question we could make far more money in much easier jobs if that were our primary concern. Given the training, hard work, stress, and debt we take on to be part of this profession, none of us are the sort of people who would sacrifice our patients or our ethics for the revenue we get from selling pet food. Very few of my clients buy their food from my hospital, and I routinely direct owners to reliable sources for fresh commercial and balanced homemade diets formulated by veterinary nutritionists. 

Unfortunately, the folks who are likely to believe vets are greedy and unconcerned about their patients’ welfare aren’t likely to be swayed by any argument or evidence. I will, however, point out that once again the alternatives to conventional diets also nearly all make money for someone, whether they are manufactured alternative diets, books written by veterinarians to promote such diets, or consultation fees these vets charge for the time they spend teaching clients about their views on nutrition. No one taking any position on what constitutes healthy nutrition for dogs and cats is doing so without some sort of bias, and potential financial bias is as likely on either side of the debate.

How Can We Best Help Our Clients?
The bottom line is that veterinarians have useful, reliable information to offer clients about nutritional choices for their pets. There is good scientific evidence to support many of our recommendations, from low-calcium and reduced calorie diets for large-breed puppies58–64 to specially formulated renal diets for elderly cats with chronic kidney disease65. As general practitioners, our fundamental understanding of physiology and nutrition is sound and useful even though we are not nutrition specialists, just as our understanding of heart disease and diabetes is sound and useful even though we are not boarded cardiologists or internists. We must recognize our own strengths and use what we know to support our clients in making well-informed choices.

One of the most useful insights we can offer many clients is that there is no “perfect” diet that will guarantee only good health for their pets, and there are few diets that are egregiously “toxic” and certain to lead to illness. Health is a complex and multifactorial state, and while nutrition is unquestionably important, simplistic notions or good and bad foods or ingredients and excessive anxiety about finding the “right” foods do more harm than good. An unhealthy obsession with selecting very specific or extreme diets for perceived health values is now widely recognized as an eating disorder in humans, usually referred to as “orthorexia.”66 Pet owners may be subject to a similar unrealistic obsession with nutrition as a means of warding off disease in their pets.

Helping pet owners to make good choices about nutrition includes helping reduce the pressure they feel that every choice is critical and will make or break their pets’ health. This is an understanding we have as healthcare professionals and which we can share with our clients.

We must also, as always, strive to do better in the area of nutrition as in all aspects of our work. Practitioners should see pursuing continuing education in nutrition from reputable sources as a necessary part of our professional development. Veterinary schools should make nutrition a stronger element of the curriculum. And we should recognize the limits of our expertise and be prepared to refer clients when they need nutritional guidance we cannot provide. Board-certified nutritionists in academic and private practice can be excellent resources in developing optimal nutritional plans for individual patients and in countering the ubiquitous myths and misinformation our clients may be exposed to. 

Finally, we should acknowledge the legitimate elements in the criticism of our knowledge and practices. While the pet food industry produces many healthful products and generates much useful resources, profit motives do influence the evidence and the education associated with industry. Clinicians need to be less eager to accept gifts and favors from representatives of industry, and we need to incorporate a recognition of potential funding bias in our critical evaluation of research evidence in the area of nutrition. The best answer to our critics and those promoting unsubstantiated and unscientific alternative approaches to evidence-based nutrition advise is not to cede the field but to work harder to meet our responsibilities to our clients and our patients.

1.          Royal College of Veterinary Surgeons. Vets amongst the most trusted professionals, according to survey – Professionals. RCVS News. Published 2019. Accessed September 4, 2020.

2.        Michel KE, Willoughby KN, Abood SK, et al. Attitudes of pet owners toward pet foods and feeding management of cats and dogs. J Am Vet Med Assoc. 2008;233(11):1699-1703. doi:10.2460/javma.233.11.1699

3.        Evason M, Peace M, Munguia G, Stull J. Clients’ knowledge, attitudes, and practices related to pet nutrition and exercise at a teaching hospital. Can Vet J. 2020;61(5):512-516. Accessed August 23, 2020.

4.        Morgan SK, Willis S, Shepherd ML. Survey of owner motivations and veterinary input of owners feeding diets containing raw animal products. PeerJ. 2017;5:e3031. doi:10.7717/peerj.3031

5.        Kamleh M. Perceptions and attitudes towards human and companion animal nutrition, nutrition education and nutrition guidance received from healthcare professionals. 2019. Accessed September 7, 2020.

6.        Flocke A, Thiemevera H, Kiefer-Hecker B. Dog and cat nutrition practices of owners visiting veterinary clinics. In: 17th Congress of the ESVCN. Ghent, Belgium; 2013.

7.        Connolly KM, Heinze CR, Freeman LM. Feeding practices of dog breeders in the United States and Canada. J Am Vet Med Assoc. 2014;245(6):669-676. doi:10.2460/javma.245.6.669

8.        Morelli G, Bastianello S, Catellani P, Ricci R. Raw meat-based diets for dogs: survey of owners’ motivations, attitudes and practices. BMC Vet Res. 2019;15(1):74. doi:10.1186/s12917-019-1824-x

9.        Lenz J, Joffe D, Kauffman M, Zhang Y, LeJeune J. Perceptions, practices, and consequences associated with foodborne pathogens and the feeding of raw meat to dogs. Can Vet J. 2009;50(6):637. Accessed August 24, 2020.

10.      Dodds WJ, Laverdure D. Canine Nutrigenomics?: The New Science of Feeding Your Dog for Optimum Health.; 2015. Accessed October 27, 2018.

11.      Pitcairn RH, Pitcairn SH. Dr. Pitcairn’s Complete Guide to Natural Health for Dogs & Cats.; 2017. Accessed October 27, 2018.

12.      Billinghurst I. Give Your Dog a Bone.; 1993. Accessed October 27, 2018.

13.      Dodd SAS, Cave NJ, Adolphe JL, Shoveller AK, Verbrugghe A. Plant-based (vegan) diets for pets: A survey of pet owner attitudes and feeding practices. Suchodolski JS, ed. PLoS One. 2019;14(1):e0210806. doi:10.1371/journal.pone.0210806

14.      Bischoff K, Rumbeiha WK. Pet Food Recalls and Pet Food Contaminants in Small Animals: An Update. Vet Clin North Am Small Anim Pract. 2018;48(6):917-931. doi:10.1016/j.cvsm.2018.07.005

15.      Becvarova I, Prochazka D, Chandler ML, Meyer H. Nutrition Education in European Veterinary Schools: Are European Veterinary Graduates Competent in Nutrition? J Vet Med Educ. 2016;43(4):349-358. doi:10.3138/jvme.0715-122R1

16.      Bruckner I, Handl S. Survey on the role of nutrition in first?opinion practices in Austria and Germany: An evaluation of knowledge, preferences and need for further education. J Anim Physiol Anim Nutr (Berl). June 2020:jpn.13337. doi:10.1111/jpn.13337

17.      Kamleh MK, Khosa DK, Dewey CE, Verbrugghe A, Stone EA. Ontario Veterinary College First-Year Veterinary Students’ Perceptions of Companion Animal Nutrition and Their Own Nutrition: Implications for a Veterinary Nutrition Curriculum. J Vet Med Educ. May 2020:e0918113r1. doi:10.3138/jvme.0918-113r1

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29.      Bazolli RS, Vasconcellos RS, de-Oliveira LD, Sá FC, Pereira GT, Carciofi AC. Effect of the particle size of maize, rice, and sorghum in extruded diets for dogs on starch gelatinization, digestibility, and the fecal concentration of fermentation products1. J Anim Sci. 2015;93(6):2956-2966. doi:10.2527/jas.2014-8409

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37.      ?rednicka-Tober D, Bara?ski M, Seal CJ, et al. Higher PUFA and n-3 PUFA, conjugated linoleic acid, ?-tocopherol and iron, but lower iodine and selenium concentrations in organic milk: a systematic literature review and meta- and redundancy analyses. Br J Nutr. 2016;115(06):1043-1060. doi:10.1017/S0007114516000349

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40.      Smith-Spangler C, Brandeau ML, Hunter GE, et al. Are Organic Foods Safer or Healthier Than Conventional Alternatives? Ann Intern Med. 2012;157(5):348. doi:10.7326/0003-4819-157-5-201209040-00007

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Examples of Negative Propaganda about Vets and Nutrition
Don’t listen to what your vet has to say about feeding your dog: vets know virtually nothing about animal nutrition… Most veterinarians have ZERO training in nutrition.

My education came from the food company representatives; those that sponsored events while I was a student, and later the food reps that visited the veterinary practices I worked in.

The dog food industry is now dominated by large multinational consumer corporations who, in my opinion, are far more interested in profit than the health of your pet. The entire pet food industry is not on the whole very ethical. Not only do they produce some pretty unhealthy stuff, they also do some pretty unethical things.
Andrew Jones, DVM
Pets Naturally Magazine
March, 2016

Because nutrition isn’t viewed as an integral part of disease management, many vet students graduate not recognizing the monumental role nutrition plays in overall health. They don’t have enough knowledge to institute innovative nutritional protocols to manage degenerative disease in their patients.

Worse still is that at many of the veterinary schools in North America, the instruction vet students DO receive comes from the biggest pet food producers in the business. Needless to say, the “training” the students receive from these companies is heavily slanted in favor of the products they sell, which are inevitably highly processed. Currently, none of the major pet food companies sell biologically appropriate diets, so these foods are portrayed as dangerous.

Unfortunately, the majority of board-certified veterinary nutritionists have also been schooled primarily about processed pet diets, and believe it or not, major pet food manufacturers frequently pay the tuition for DVMs studying to become veterinary nutritionists. So when a veterinary nutritionist recommends X, Y or Z food — or discourages feeding raw or homemade diets, which is common — keep in mind that many practicing veterinary nutritionists are obligated in some way to a pet food manufacturer.

Karen Becker, DVM
Healthy Pets, Mercola.Com
July, 2017

The problem with your average veterinarian giving you nutritional advice is that they have had very little nutrition training… Most vets get their information from other biased or uninformed vets, they believe what they read in the vet publications sponsored by kibble companies, they get their info from sales representatives of the big kibble companies or from limited private reading. I am sure you understand why kibble companies do not make the best reference source as they are only interested in selling their products and are not open to alternative diets even if that might be actually needed.

Jennifer Carter
Volhard Dog Nutrition
January, 2020

How much do veterinarians learn about nutrition? The sad answer is not a lot, and often our information is biased…the doctors graduating from veterinary schools are biased at best. At worst, they are very “anti-natural” and rabid fans of these national brands…Most well-known pet food companies have been sold to mega conglomerates like Colgate-Palmolive, who often add plant and animal by-products and various chemical preservatives, additives, flavorings, and colorings to the products. 

Doctors must strike out on their own to seek a more balanced approach to diet and nutrition.  But they are not inclined to do this unless they are driven to expand beyond conventional medicine. Since most are satisfied with the status quo, it is hard to find a veterinarian who is not afraid to challenge his long-held beliefs and actually look at other dietary and nutritional options for his patients. 
Shawn Messonier, DVM
Animal Wellness Magazine

Hills, Purina, and Iams are ingrained into the consciousnesses of every veterinarian from their professional infancy to their grave. Processed food is in our blood – Yuck. How can you expect a veterinarian to be open to the idea that real, raw food is anything but dangerous for pets?

Veterinary students learn about dog and cat nutrition from a book written by a major pet food company. The nutritionist that teaches them has usually had their education underwritten by a major pet food company. Major pet food companies provide free food for vet students and also the teaching hospitals where they are learning about veterinary norms.

Who has money to fund research into pet nutrition? You guessed it, the major pet food companies. Most continuing education for veterinarians regarding nutrition is sponsored by pet food companies. 

My hope is that the grassroots, raw pet food movement will cause more vets to see the light as they encounter healthy animals being fed these diets. Perhaps the conventional nutrition programming can be unlearned and the eyes of veterinarians opened to the truth.

Doug Knueven, DVM
Blog Post
May, 2014

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From SkeptVet TV- “Natural” Remedies & Placebos in Pets

I’ve added a couple of short videos on the subjects of “natural” remedies and placebo effects in pets to my YouTube channel, SkeptVet TV.

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The Latest on Dietary Risk Factors for Dilated Cardiomyopathy (DCM) & Misleading Media Spin by Grain-free Diet Manufacturers

Along with many in the veterinary profession, I have been following the concerns about diet-associated heart disease in dogs since 2018. A type of severe disease known as dilated cardiomyopathy (DCM) has been reported in dogs not previously thought prone to developing this malady, and it has been associated with the feeding of certain diets. These include grain-free diets, diets with exotic protein sources, and diets produced by small-scale or “boutique” manufacturers. Collectively, these foods have been referred to in some scientific papers as “BEG” diets.

Here are my previous posts on the subject-

Grain-free Diets and Heart Disease in Dogs– August, 2018

Evidence Update: Grain-free and other “BEG” Diets Associated with Heart Disease in Dogs– December, 2018

FDA Update on Grain-free Diets and Heart Disease in Dogs– January, 2019

I also recently wrote an article for Veterinary Practice News on the subject critically evaluating a narrative literature review that seemed to dismiss concerns about BEG diets and DCM. Unfortunately, this review had a number of limitations, including selective reporting of relevant findings and an undisclosed conflict of interest. Some of the authors are employees of a company which produces grain-free diets and which is actively campaigning against the idea that these diets could have negative health effects. BSM, the research group behind the review, has also accepted grant funding from a manufacturer of ingredients for grain-free diets for further research into the subject, which raises concerns about the risk of funding bias.

My most recent conclusion on the subject was this:

The scientific issue, meaning the potential causal relationship between various nutritional factors and DCM, is unresolved. Further research will be needed to confirm or refute hypotheses about any causal role of pulses, exotic protein sources, and boutique pet foods in this disease. As new research is published, however, reviewers and readers should take into account the role of financial considerations of the conclusions of various stakeholders, and the relevance of these impacts to the potential for bias in the conduct and analysis of the research.

About the same time my article was published, a virtual conference on the subject of DCM was held through Kansas State University in September, 2020

This conference included a statement from an official of the FDA Center for Veterinary Medicine (CVM), presentations by several pet food manufacturers and representatives of industry, reports from members of the BSM research group responsible for the review article I mentioned earlier, and other research presentations. Some of the abstracts and presentations are available on the conference web site while others are not. None of the presentations refer to published, peer-reviewed research. 

Not surprisingly, representatives of industry and BSM were highly critical of the hypothesis that diet might be associated with DCM in dogs, and they provided arguments and limited unpublished data to contradict this hypothesis. Other researchers provided similarly unpublished data showing that dogs with DCM who were fed BEG diets recovered from the disease with diet change and supplementation of the amino acid taurine, data which supports the hypothesized causal relationship between these diets and DCM. The FDA official was studiously neutral on the scientific question, trying to explain the role of the agency in monitoring pet food safety and keeping the public informed while not unnecessarily interfering with the interests of the pet food industry.

None of the information presented at the conference establishes a definitive answer to the role of diet in DCM, and the question requires further research to answer. However, several manufacturers have since made public statements egregiously misrepresenting the state of the science and the position of the FDA. Champion Pet Foods, for example, issued this deceptive press release:

FDA Provides Clarity About Canine Heart Disease and Diet- Evidence Finds No Causal Relationship to Grain-Free Food

BOULDER, COLORADO, November 5, 2020 – The U.S. Food and Drug Administration (FDA) issued an update this week that concluded there is no scientific evidence that a grain-free diet causes canine dilated cardiomyopathy (DCM). The agency outlined the multiple potential factors that can, alone or in combination, contribute to dogs developing this rare and scientifically complex disease. The agency concluded that there is nothing inherently unsafe about a grain-free diet. This is good news for pet lovers everywhere who, for years, have seen their dogs thrive on grain-free diets for healthy and wholesome nutrition.

This misrepresents the most recent statement from the FDA, which does not offer any such conclusion:

Historically, DCM has been primarily linked to genetic predisposition in certain breeds, but in the context of these atypical cases, emerging science appears to indicate that non-hereditary DCM is a complex medical condition that may be affected by the interplay of multiple factors such as genetics, underlying medical conditions, and diet.

FDA has not taken regulatory action against or declared any specific pet food products unsafe or definitively linked to DCM. As the scientific community looks further into the role that diet may play in these cases, we hope to explore additional avenues about ingredient levels, nutrient bioavailability, ingredient sourcing, and diet processing to determine if there are any common factors. We have asked pet food manufacturers to share diet formulation information, which could substantially benefit our understanding of the role of diet.

FDA sees this as an ongoing, collaborative, multidisciplinary scientific venture… to assess the available information and fill data gaps to determine what factors may contribute to the development of non-hereditary DCM.

Other industry organizations have issued similar statements implying that the FDA has concluded there is no causal relationship between DCM and diet, when in reality the agency has merely left the question open for further study. 

Science inherently involves controversy. It functions best as a process focused on challenging and striving to prove hypotheses wrong. By its very nature, the scientific method requires criticizing the research of other scientists in order to expose bias and error in hypotheses and research methods. Unfortunately, this necessary level of controversy is unnecessarily exacerbated by the influence of ego, reputation, career goals, and money on how individual defend or attack scientific hypotheses and data. The issue of diet and DCM illustrates both the inevitable and the unnecessary conflict involved in the assessment of new ideas by the scientific community.

The core question, whether certain diets or ingredients or methods of formulation have a causal role in DCM and how, precisely, this might work remains unanswered. Those researchers hypothesizing a causal relationship and investigating this idea have always been careful to point out that the data is not yet clear nor definitive. The FDA has also been clear that they are responsible for informing the public of and investigating potential risks, but the agency has made no firm conclusion on the role of diet in DCM. 

While it is understandable that critics of this hypothesis would try to undermine the arguments and evidence put forward by proponents, it is unfortunate when this is done in a disingenuous or outright misleading way. And though, undoubtedly, these critics have a genuine skepticism of the hypothesis based on the limited evidence available, the role of financial bias cannot be ignored. The publication of concerns that grain-free diets might lead to DCM, and the word-of-mouth among breed groups and pet owners with firsthand experience of this disease, have significantly affected sales of these diets. It would be naïve to imagine that manufacturers of BEG diets are unaffected in their opinions by this fact.

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