Recent Canine Aging Science Articles

If my posts have seemed few and far between lately, one of many reasons is I have been busily typing away producing some scientific publications in my new focus area- canine aging science. My collaborators and I have produced several recent papers which I hope will be of some interest to some of you. Since not all are readily available outside of academia, I will post them here. Enjoy!

McKenzie, BA. Chen, FL. Gruen, ME. Olby, NJ. Canine Geriatric Syndrome: A Framework for Advancing Research in Veterinary Geroscience . Front Vet Sci. 9:853743. April, 2022.

Biological aging is the single most important risk factor for disease, disability, and ultimately death in geriatric dogs. The effects of aging in companion dogs also impose significant financial and psychological burdens on their human caregivers. The underlying physiologic processes of canine aging may be occult, or early signs of aging may be ignored because of the misconception that biological aging is natural and therefore inevitable. The ability to detect, quantify, and mitigate the deleterious processes of canine aging would greatly enhance veterinary preventative medicine and animal welfare. In this paper we propose a new conceptual framework for aging in dogs, the Canine Geriatric Syndrome (CGS). CGS consists of the multiple, interrelated physical, functional, behavioral, and metabolic changes that characterize canine aging as well as the resulting clinical manifestations, including frailty, diminished quality of life, and age-associated disease. We also identify potential key components of a CGS assessment tool, a clinical instrument that would enable veterinarians to diagnose CGS and would facilitate the development and testing of interventions to prolong healthspan and lifespan in dogs by directly targeting the biological mechanisms of aging. There are many gaps in our knowledge of the mechanisms and phenotype of aging in dogs that must be bridged before a CGS assessment tool can be deployed. The conceptual framework of CGS should facilitate identifying these gaps and should stimulate research to better characterize the processes and effects of aging in dogs and to identify themost promising preventative strategies to target these.

McKenzie, BA. Comparative Veterinary Geroscience: Mechanism of molecular, cellular, and tissue aging in humans, laboratory animal models, and companion dogs and cats. Amer J Vet Res. 2022;83(6:). 

Aging is the single most important cause of disease, disability, and death in companion animal species. Contrary to the common view of aging as mysterious and inevitable, it is more usefully understood as a set of complex but comprehensible and modifiable biological processes that are highly conserved across species. The purpose of this Currents in One Health manuscript is to describe key mechanisms of aging at the cellular and molecular level and the manifestations of these in the tissues of the musculoskeletal system, adipose, and the brain. The characteristics of these processes as identified in common laboratory animal models and in humans will be described and compared with the much more limited information available concerning aging in dogs and cats. This will highlight important targets for future research in these species. The consistent patterns across species in the hallmarks of aging and their manifestations at the level of tissues, organ systems, and individual animals signify potential targets for interventions to mitigate the negative health impacts of aging and extend both life span and health span (the period of life free of significant disease or disability). Further research to elucidate aging mechanisms in companion dogs and cats will eventually support development, testing, and implementation of clinical therapies to prevent and ameliorate age-related dysfunction, disease, and death.

McKenzie, BA. Lacroix-Fralish, ML. Chen, F. The phenotype of aging in the dog: How aging impacts the health and wellbeing of dogs and their caregivers. J Amer Vet Med Assoc. 2022;260(9):963-970. 

Aging is the single most important cause of disease, disability, and death in adult dogs. Contrary to the common view of aging as a mysterious and inevitable natural event, it is more usefully understood as a set of complex but comprehensible biological processes that are highly conserved across species. Although the phenotypic expression of these processes is variable, there are consistent patterns both within and between species. The purpose of this feature is to describe the patterns currently recognized in the physical and behavioral manifestations of aging in the dog and how these impact the health and welfare of companion dogs and their human caregivers. Important gaps in our knowledge of the canine aging phenotype will be identified, and current research efforts to better characterize aging in the dog will be discussed. This will help set the context for future efforts to develop clinical assessments and treatments to mitigate the negative impact of aging on dogs and humans.

Posted in Aging Science | 6 Comments

Are Vegan Diets Healthier for Dogs & Cats?

Given the media frenzy the article has kicked off, it is unlikely very many people are unaware of a recent study reported in the journal PLOS One that claims to show vegan diets are healthier for dogs and cats than diets containing meat. 

Knight A, Huang E, Rai N, Brown H. Vegan versus meat-based dog food: Guardian-reported indicators of health. PLoS One. 2022 Apr 13;17(4):e0265662.

Dramatic headlines have appeared in many major news sources proclaiming that vegan diets are “linked to better health” or “are healthier and safer” than conventional diets. Getting beyond the headlines, one may even read that this study demonstrates raw diets to be healthier than conventional foods, though that is less emphasized in both the original article and the media coverage.

I’ve written about vegan diets for dogs before, and indeed this article cites my column on the subject, though only to dismiss my claim that vegan diets “should not be recommended” as “without evidence.” This is not entirely accurate, since my article did cite the limited evidence available, and I did not actually recommend against vegan diets for dogs, though I did conclude they were a bad choice for cats. My actual claims were:

There is no evidence vegetarian diets have health benefits for dogs and cats, and no real reason to believe they should, based on the physiology and nutritional requirements of these species.

Dogs are omnivores that are able to eat both plant and animal foods, and in theory, they should be able to thrive on vegetarian or vegan diets. However, these diets must be carefully formulated, and many commercial vegetarian dog foods do not appear to be nutritionally adequate. There is also little reliable research evidence showing dogs can remain healthy when fed only a vegan diet. Given the unexpected health problems seen with theoretically adequate grain-free diets, we should be cautious about the potential risks of vegetarian formulations for dogs until there is better and more evidence showing their long-term health effects.

Cats are clearly obligate carnivores with nutritional requirements that are unlikely to be effectively met by vegan diets. Such diets offer only risks and no benefits for cats and should be avoided.

In any case, I am sympathetic to many of the potential environmental and health benefits of plant-based diets, and I have been a vegetarian, though not a vegan, for almost 20 years  (technically, an ovo/lacto/pescatarian, though realistically I don’t like fish and so eat very little of it). However, the evidence for benefits of plant-based diets for dogs and cats is far weaker than that for humans, which is itself often nuanced and not always conclusive. And I believe in following the evidence wherever it leads, even when it doesn’t support my personal beliefs or practices.

So, does this paper change the game in terms of showing real health benefits to raw and/or vegan diets? Spoiler, but not really! Let’s look at the actual findings a bit closer.

The Study- Results
The study reported the following statistically significant differences between “conventional,” raw, and vegan diets (leaving aside the fuzzy definitions of these, the ubiquitous feeding of unidentified treats to all pets, and the lack of clarity about how strictly feeding practices corresponded to each category).

  • Dogs fed raw and vegan diets were less likely to have had multiple veterinary visits in the year observed.
  • Dogs fed raw and vegan diets were less likely to have been given medications
  • Dogs fed raw and vegan diets were less likely to have been transitioned onto a therapeutic diet
  • Dogs fed raw and vegan diets were less likely to have an owner-reported veterinary assessment of poor health status
  • Dogs fed raw and vegan diets were less likely to have an owner reported assessment of poor health
  • Dogs fed raw and vegan diets were less likely to be reported to be “unwell,” and when unwell dogs on raw diets had fewer reported disorders than dogs on conventional diets.
  • There were differences in the occurrence of specific health conditions between diet groups as illustrated in this figure and table:
  • Dogs fed raw and vegan diets were less likely to have had multiple veterinary visits in the year observed.
  • Dogs fed raw and vegan diets were less likely to have been given medications
  • Dogs fed raw and vegan diets were less likely to have been transitioned onto a therapeutic diet
  • Dogs fed raw and vegan diets were less likely to have an owner-reported veterinary assessment of poor health status
  • Dogs fed raw and vegan diets were less likely to have an owner reported assessment of poor health
  • Dogs fed raw and vegan diets were less likely to be reported to be “unwell,” and when unwell dogs on raw diets had fewer reported disorders than dogs on conventional diets.
  • There were differences in the occurrence of specific health conditions between diet groups as illustrated in this figure and table:

All-in-all, these results would seem to be pretty bad news for conventional diets (whatever that means) and pretty good news for feeders of raw and vegan diets. Anyone reading this, however, can probably sense the “but” coming, so let’s get into the caveats.

The Study-Limitations
The biggest limitation (and boy is it a big one!) is that all the data were collected from online surveys of pet owners. Everything from the diet fed to the health status and even the reported veterinary assessment of health all relied entirely on the responses of pet owners who found the survey online and took the trouble to complete it. None of the facts, not the feeding practices nor the health of the pets, were verified objectively in any way. Right from the start, then, that makes this a study of what some small subset of pet owners believe about their pets’ diet and health, not about the actual feeding and health of these animals.

It is not difficult to find reasons to be concerned that these responses may not reflect reality, or even the opinions of other groups of pet owners. The respondents were overwhelmingly female (92%) and European (86%), which is a pretty narrow population to survey. They were, of course, also in a socioeconomic class inclined to participate in online pet health surveys, which is also not representative of many other pet owners.

More concerning, 22% of the population of owners were themselves vegan. This is a group likely to have strong beliefs and biases about plant-based vs meat-based nutrition and health, so it would be, frankly, shocking if they did not report that plant-based diets were healthier than other diets. 13% of these owners fed their pets vegan diets and 33% fed raw meat, indicating nearly half fed unconventional diets not usually recommended by veterinarians or veterinary nutrition specialists. Such a group is clearly a population biased in favor of the kind of outcomes reported in this study, and given the study only shows us the opinions of owners, not actual objective data about health and diet, the outcomes are simply a fancy way of reporting what people in this group think. 

Other studies in other populations have reported lower rates of veganism (5.8%) and of feeding vegan diets to pets (1-3%), which emphasizes that this study surveys a very specific, narrow group of owners. A review of previous owner surveys also shows more nuanced and variable feeding practices reported in these studies, again suggesting this paper may not be applicable outside of the specific population included in the survey.

In terms of potential sources of bias beyond the survey population, it is worth pointing out that the lead author is a consistent advocate for plant-based diets, for humans and pets, on environmental and ethical grounds. The study was also funded by a plant-based diet advocacy group. As I have discussed in detail in previous articles on conflict of interest, these facts do not indicate the research is fraudulent or inaccurate, nor are they a justification for ignoring the claims, arguments, and evidence provided in this paper. They are, however, a reason to consider carefully the potential for uncontrolled unconscious bias in the design, conduct, analysis, and reporting of the study. Given that the study itself was essentially a survey of subjective opinions, methods to control such bias are minimal, so the results have to be viewed in that context.

The authors, to their credit, do acknowledge some of these limitations. They call out the fact that, for example, fewer reported veterinary visits in dogs fed raw diets may be due to the fact that feeders of raw diets are often skeptical of conventional veterinary medicine and less likely to seek care rather than to any actual difference in health status. The same logic, of course, applies to the frequency of vet visits for dogs fed vegan diets, and to the reported use of medicine and therapeutic diets by owners who have a clear preference for unconventional health practices to begin with.

So what does this study mean? Overall, it means that the particular population of pet owners surveyed believes that feeding raw and plant-based diets are associated with better health in their pets. They also believe that their veterinarians think their pets are healthier (though whether these vets actually believe this is unknown). And these owners report less use of veterinary medical services, though whether this means their pets are healthier or simply that they try harder to avoid taking their pets to the vet is also unknown.

Like previous studies relying on owner surveys and both conducted and funded by folks with strong a priori opinions about diet and health, this is a useful insight into such beliefs. It is not compelling or probative evidence for actual health effects of different feeding strategies. Sadly, the media coverage of the paper rarely recognizes or emphasizes this.

As the authors themselves suggest, though with little evident enthusiasm, controlled studies with objective measures of outcome and more defined and verified feeding practices are required to draw any meaningful, actionable conclusions about the healthiest feeding strategy for our pets. I am neither for nor against vegan diets for dogs, and I am even open to reversing my objection to feeding vegan to cats or raw diets to cats or dogs if strong evidence is generated that these are safe or beneficial practices. However, regardless of the difficulties in funding and conducting the necessary research, we are not justified in making confident claims about the health impact of raw, vegan, or conventional diets without it.

Posted in Nutrition | 16 Comments

Do Dogs Like Music? (Evidence Update)

Over the roughly 13 years I have been writing this blog, I have covered quite a few different topics, though with all I have maintained the central theme of evaluating claims about pet health from a science-based perspective. Part of this perspective is keeping track of the changing evidence as new research results become available. This can be tough as the number of topics, and the volume of evidence, grows over such a long period. 

Today, I am returning briefly to a topic I previously covered in 2015 and twice in 2017 (A and B). As often proves to be the case, my conclusions have remained relatively unchanged, though this is one area in which I began with, and have maintained, some cautious optimism.

While it is very likely some kinds of music can be beneficial to our pets and veterinary patients under some circumstances, the devil is, as usual, in the details, and we don’t know much about the details yet. It is reasonable to experiment with music in veterinary environments, especially with more quiet, instrumental genres, but we must try to develop objective measures of the effect to be sure we are not imply wasting our effort or, even worse, actually adding stress for our patients.

2017- January
On balance, then, I think it is possible that music might have some benefits for dogs in stressful circumstances, such as boarding kennels, hospitals, and shelters, but this is by no means clearly proven. The risk is also likely quite low, so there is probably little harm in using quiet music for this purpose so long as it is not substituted for other, more comprehensive approaches to reducing stress and anxiety.

2017- July
The existing evidence is weak and inconsistent, so no clear conclusion can be drawn. In this study, there was no sign of any effect of classical music or the same music digitally altered with the goal of reducing stress in dogs. The question remains open, and definitive claims for or against the potential effects of music in this situation are not justified.

My reason for revisiting the topic now is that I have run across a systematic review looking at al the available evidence up through 2019.

Lindig AM, McGreevy PD, Crean AJ. Musical Dogs: A Review of the Influence of Auditory Enrichment on Canine Health and BehaviorAnimals. 2020; 10(1):127. 

Systematic reviews are incredibly useful as they provide a comprehensive evaluation of the available scientific literature with an explicit focus on evaluating the strengths and weaknesses of the available evidence. They are never, of course, completely without bias, and they can often be frustrating since they rarely allow definitive conclusions or a high level of confidence in a particular interpretation of the evidence. But having such a review gives us a reasonable chance of getting a good overview of the subject and the evidence.

The conclusions of this review track pretty well with my own assessments in the past:

Interest in the use of music therapy as a behavioral enrichment tool in veterinary medicine is growing. Indeed, an industry has formed around the development of ‘dog music’, which has been purposely designed to relax dogs. Despite enthusiastic uptake of the idea, there is little empirical evidence supporting the design of such tools… As a general observation, animals appear less stressed or anxious when exposed to classical music than to control conditions. [This review] also acknowledges that this field is relatively under-researched, and more rigorous studies must be conducted before species-specific recommendations can be made. Such studies must reflect individuals’ and species’ preferences for different genres and songs, taking care to avoid habituation.

The best we can say about the value of music for dogs is that a few studies have shown short-term changes in behavior and some physiologic measurements that suggest quiet genres of music, such as classical, may have a calming effect on some dogs in some circumstances. Sounds specifically designed for dogs don’t’ seem to have any more effect than classical music. These short-term effects may wane with repeated exposure to the same music. And there is virtually no research on the long-term effects of music exposure, the potential health effects, and the importance of breed and individual differences or preferences.

Posted in General | 5 Comments

Does eating a Raw Diet as a Puppy Reduce later Allergy Risk?

I have written many times about the controversial subject of raw diets for dogs. The bottom line, based on existing evidence, is there are no proven health benefits to these diets and several well-documented risks, including infectious disease and nutritional inadequacy.1

Proponents of these diets offer varied theoretical arguments for why they should be healthier than commercial cooked foods. Many are simply fallacious claims about what is “natural” or “ancestral.” However, there are some plausible, but unproven hypotheses, about the potential negative health impacts of conventional diets or the possible health benefits of feeding uncooked meat.

Concerns about Maillard reaction products (MRPs) in cooked foods, for example, are reasonable given the potential carcinogenicity of some of these compounds at some amounts in some species. However, it is far from evident these compounds actually do cause harm in the form and amount found in cooked dog foods, and research has identified potential benefits as well as risks to their consumption, so the assumption that cooked foods must be unhealthy because they contain MRPs is unreasonable.2

Similarly, the hypothesis that exposure to microorganisms during development can reduce the subsequent risk of allergies and other immune-system diseases is plausible, and there is some supportive evidence, though there is also evidence against this “hygiene hypothesis.”3-6 However, this does not justify the assertion that exposure to such organisms through eating raw meat, dirt, or other substances, has more benefits than risks.

A recent paper published in the Journal of Veterinary Internal Medicine (JVIM) purports to support claims for health benefits from raw diets.7 

Hemida MBM, Salin S, Vuori KA, et al. Puppyhood diet as a factor in the development of owner?reported allergy/atopy skin signs in adult dogs in Finland. J Vet Intern Med. 2021;35(5):2374-2383.

The authors suggest exposure to raw diets in puppies may reduce the risk of later development of canine atopic dermatitis (CAD), and exposure to conventional commercial diets may increase CAD occurrence in adulthood. There are, however, numerous limitations and red flags associated with this study, and it is not strong evidence.

The authors of the paper have a long history of promoting raw diets and various alternative therapies, and they have a clear bias on the subject.8-16 Of course, researchers often have confident beliefs, rather than tentative hypotheses, when they design and conduct scientific studies. It is well-established that “researcher degrees of freedom,” the amount of leeway investigators have in designing studies and in collecting and analyzing data, is associated with the likelihood of false-positive results.17

Given researchers with clear a priori beliefs about raw diets designed the survey, defined the variables of interest, and had total freedom to create and conduct the regression analysis, the results likely reflect the beliefs of the researchers more than the underlying reality of nature.

One example of the clear bias behind this study is in the terminology chosen for different diet categories. They divide foods into “non-processed meats/ingredients” and “ultra-processed carbohydrate-rich foods.” These are artificial categories reflecting the ideological bias of the researchers, not the reality of the kinds of foods dogs are actually fed.

“Non-processed” is meaningless unless the dogs are eating whole prey and plants they find for themselves. Likewise, the term “ultra-processed” is also an inappropriate extrapolation of terms used to describe human snack foods, which are not meaningfully similar to commercial pet foods. The label is a value judgment that implies a negative health impact not actually proven to exist.

Commercial canned and dry foods are also not accurately described as “carbohydrate-rich.” The carbohydrate content of commercial dry diets varies dramatically, as does the type of carbohydrate (from simple sugars to complex fibers). The nutritional value and potential health effects of commercial diets will vary greatly based on these differences, and lumping them all together in this artificial category is not a sound scientific approach.

Another potential influence on this study is funding bias. It is, again, well-established that funding sources can influence the outcomes of research, which is why disclosure of funding sources is required by scientific journals.18 In a web documentary called The Dog Cancer Series, one of the authors of this study herself cites funding bias as a factor in the literature concerning raw diets:

“[Raw food is] not really researched in universities. Most universities get sponsored by these big billion-dollar companies, and you don’t really want to step on their toes, I guess. But, I think that’s not really ethical,” says Dr. Anna Hielm-Bjorkman.19

It is relevant, then, to point out this study received financial support from raw diet manufacturers, as well as Dr. Joseph Mercola, an infamous proponent of alternative medicine and anti-vaccine activist repeatedly warned by the Food and Drug Administration (FDA) for promoting COVID-19 misinformation and selling unproven treatments.20,21 Given the potential for ideological and funding bias in this research project, the lack of rigorous controls for possible bias in this study is concerning.

The main source of data is an online survey available only in Finnish. This is a very narrow sample population, and it is unlikely to be representative of the views or practices of dog owners generally.

More importantly, the responses are simply expressions of the perceptions and beliefs of the owners who participated, not necessarily the nutritional and environmental exposures nor health outcomes actually experienced by the dogs. Self-reporting of diet and health information has been shown to be unreliable in humans, and it is unlikely to be more reliable among dog owners.22,23

Previous reports evaluating this source of data do not inspire confidence.2,15 The researchers validated responses by emailing respondents and looking for consistency in their answers to selected questions. In a previous study, only about 30 percent of the respondents replied to these emails, and almost 13 percent of responses to this survey tool were discarded as “robot” answers. Also, 26 percent of respondents provided inconsistent or discordant answers regarding diet and CAD symptoms.15

The current study reports 4.2 percent of answers were discarded as duplicates or robot responses, but provides no information on discordant responses. The report does indicate, however, 31 percent of the responses were discarded because an analysis of the foods reported indicated significant underfeeding.7

It seems more likely owners were misremembering their feeding practices rather than 30 percent of owners were dramatically underfeeding their dogs.

Asking owners to remember in great detail what they fed their puppy between two to eight months of age, and then trying to associate this with health outcomes years later, is a questionable strategy. With no direct or objective verification, it seems very likely the dietary and health information reported in this survey is unreliable.

The associations discovered during statistical analysis support this interpretation because they are often inconsistent and make no obvious sense in terms of the authors’ hypothesis that raw foods are protective against CAD. For example, why would raw tripe and organ meats be protective, but raw red meat, eggs, and poultry would not be?

If cooking is the main risk factor, why would cooked vegetables be protective and raw vegetables would not? Why would both cooked and raw eggs be protective while neither cooked nor raw poultry is associated with the likelihood of CAD? If exposure to bacteria is the main variable, why is eating dirt, sticks, or carcasses protective, but eating clay and grass is not, and drinking from puddles is actually associated with increased risk?

If excessive processing is the issue, why was there no association with eating processed meats or canned foods, and only a marginal association with dry food when it was the only food offered?

Additionally, the paper reports associations between the proportion of various foods fed and adult CAD risk that are hard to explain.

Dogs with CAD were more likely to be eating no raw food at all than controls, and dogs without CAD were more likely to be fed 20 percent or 90 percent raw, but there were no differences at any other ratio of the two foods. Similarly, allergic dogs were more likely to be fed 80 percent dry than controls, but there was no significant difference if they were fed more than 80 percent dry.

Control dogs were more likely to be fed 50 percent or less than 10 percent dry, but there was no difference at intermediate ratios. It is easier to see cherry picking and researcher degrees of freedom than a consistent dose-response in these results.

Identifying causal associations between nutrition and health outcomes is inherently difficult. Available feeding strategies involve many differences in nutrient form and content other than the narrow aspects we may choose to focus on, such as cooked versus raw.

It is worth conducting research to investigate such relationships, but strong evidence will always be scarce and difficult to produce. However, productive research efforts must involve meaningful attempts to control for bias and to obtain fundamentally reliable data, even when conclusions may always have to be tentative.

The authors of this study continue to publish papers suggesting health benefits to raw diets and risks to conventional diets based on a single online survey tool and a convenience sample of Finnish-speaking dog owners. This is never going to be a solid data set upon which useful conclusions can be based, and the research produced from it are more likely to be an expression of the beliefs and perceptions of the respondents and the researchers, rather than a sound representation of the complex relationships between nutrition and health.

Brennen McKenzie, MA, MSc, VMD, cVMA, discovered evidence-based veterinary medicine after attending the University of Pennsylvania School of Veterinary Medicine and working as a small animal general practice veterinarian. He has served as president of the Evidence-Based Veterinary Medicine Association and reaches out to the public through his SkeptVet blog, the Science-Based Medicine blog, and more. He is certified in medical acupuncture for veterinarians. Columnists’ opinions do not necessarily reflect those of Veterinary Practice News.


  1. McKenzie B. Debating Raw Diets. Vet Pract News. January 2019:30-31.
  2. Roine J, Uusitalo L, Hielm-Björkman A. Validating and reliability testing the descriptive data and three different disease diagnoses of the internet-based DOGRISK questionnaire. BMC Vet Res. 2016;12(1):30. doi:10.1186/s12917-016-0658-z
  3. Brooks C, Pearce N, Douwes J. The hygiene hypothesis in allergy and asthma. Curr Opin Allergy Clin Immunol. 2013;13(1):70-77. doi:10.1097/ACI.0b013e32835ad0d2
  4. Kemp A, Björkstén B. Immune deviation and the hygiene hypothesis: A review of the epidemiological evidence. Pediatr Allergy Immunol. 2003;14(2):74-80. doi:10.1034/j.1399-3038.2003.00017.x
  5. Tizard IR, Jones SW. The Microbiota Regulates Immunity and Immunologic Diseases in Dogs and Cats. Vet Clin North Am Small Anim Pract. 2018;48(2):307-322. doi:10.1016/j.cvsm.2017.10.008
  6. Lynch S V, Wood RA, Boushey H, et al. Effects of early-life exposure to allergens and bacteria on recurrent wheeze and atopy in urban children. J Allergy Clin Immunol. 2014;134(3):593-601.e12. doi:10.1016/j.jaci.2014.04.018
  7. Hemida MBM, Salin S, Vuori KA, et al. Puppyhood diet as a factor in the development of owner?reported allergy/atopy skin signs in adult dogs in Finland. J Vet Intern Med. 2021;35(5):2374-2383. doi:10.1111/jvim.16211
  8. Hielm-Björkman A, Reunanen V, Meri P, Tulamo R-M. Panax Ginseng in combination with brewers’ yeast (Gerivet) as a stimulant for geriatric dogs: a controlled-randomized blinded study. J Vet Pharmacol Ther. 2007;30(4):295-304. doi:10.1111/j.1365-2885.2007.00876.x
  9. Teixeira LR, Luna SPL, Matsubara LM, et al. Owner assessment of chronic pain intensity and results of gait analysis of dogs with hip dysplasia treated with acupuncture. J Am Vet Med Assoc. 2016;249(9):1031-1039. doi:10.2460/javma.249.9.1031
  10. Hielm-Björkman A, Tulamo R-M, Salonen H, Raekallio M. Evaluating complementary therapies for canine osteoarthritis–Part II: a homeopathic combination preparation (Zeel). Evid Based Complement Alternat Med. 2009;6(4):465-471. doi:10.1093/ecam/nem143
  11. Rosendahl S, Anturaniemi J, Vuori KA, Moore R, Hemida M, Hielm-Björkman A. Diet and dog characteristics affect major and trace elements in hair and blood of healthy dogs. Vet Res Commun. November 2021. doi:10.1007/s11259-021-09854-8
  12. Hakanen E, Lehtimäki J, Salmela E, et al. Urban environment predisposes dogs and their owners to allergic symptoms. Sci Rep. 2018;8(1):1585. doi:10.1038/s41598-018-19953-3
  13. Anturaniemi J, Barrouin-Melo SM, Zaldivar-López S, Sinkko H, Hielm-Björkman A. Owners’ perception of acquiring infections through raw pet food: a comprehensive internet-based survey. Vet Rec. 2019;185(21):658. doi:10.1136/vr.105122
  14. Fredriksson-Ahomaa M, Heikkilä T, Pernu N, Kovanen S, Hielm-Björkman A, Kivistö R. Raw Meat-Based Diets in Dogs and Cats. Vet Sci. 2017;4(3). doi:10.3390/vetsci4030033
  15. Hemida M, Vuori KA, Salin S, Moore R, Anturaniemi J, Hielm-Björkman A. Identification of modifiable pre- and postnatal dietary and environmental exposures associated with owner-reported canine atopic dermatitis in Finland using a web-based questionnaire. PLoS One. 2020;15(5):e0225675. doi:10.1371/journal.pone.0225675
  16. Hemida MBM, Salin S, Vuori KA, et al. Puppyhood diet as a factor in the development of owner?reported allergy/atopy skin signs in adult dogs in Finland. J Vet Intern Med. 2021;35(5):2374-2383. doi:10.1111/jvim.16211
  17. Simmons JP, Nelson LD, Simonsohn U. False-positive psychology: undisclosed flexibility in data collection and analysis allows presenting anything as significant. Psychol Sci. 2011;22(11):1359-1366. doi:10.1177/0956797611417632
  18. Resnik DB, Elliott KC. Taking financial relationships into account when assessing research. Account Res. 2013;20(3):184-205. doi:10.1080/08989621.2013.788383
  19. Habib R, Becker K. The Dog Cancer Series: Rethinking the Cancer Epidemic Vol. 1- Chapter 4 (Transcript).; 2018:73.
  20. Satija N, Sun L. A major funder of the anti-vaccine movement has made millions selling natural health products. Washington Post. December 20, 2019.
  21. Science A for. FDA warns Mercola: Stop selling fake COVID remedies and cures.
  22. Fadnes LT, Taube A, Tylleskär T. How to identify information bias due to self-reporting in epidemiological research. Internet J Epidemiol. 2009;70(2). Accessed December 23, 2021.
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Posted in Nutrition | 4 Comments

PEMF (Assisi Loop) for Separation Anxiety in Dogs- A new Study

A recurring topic here over the years has been pulsed electromagnet field therapies. I have reviewed evidence concerning these in 2009 and 2020 (twice), and my conclusions have always been-

  • The therapy is biologically plausible
  • The evidence is weak
  • The claims for these devices routinely go well beyond the available evidence

A reader recently drew my attention to a new study that is a follow-up of a previous pilot trial

Pankratz K, Korman J, Emke C, Johnson B, Griffith EH, Gruen ME. Randomized, Placebo-Controlled Prospective Clinical Trial Evaluating the Efficacy of the Assisi Anti-anxiety Device (Calmer Canine) for the Treatment of Canine Separation Anxiety. Front Vet Sci. 2021 Dec 20;8:775092. 

The good news is that the study is very well designed, with appropriate controls for many important sources of bias and error. The subjects were selected and randomized appropriately, and everyone was properly blinded. Both a subjective owner measure of effect and objective blinded analysis of video were used to assess effects. There were also active and matched sham devices employed.

As always, there were some limitations to the study. Dogs with behavioral problems other than separation anxiety (SA), such as noise phobia, were excluded. While this makes sense to simplify the study, such problems are common in dogs with SA, so the subjects may not represent the population of SA dogs likely to be treated in the real world. 

Dogs were also on varied medications, and none were given a behavior modification program, as would normally be done for this condition, so again how treatment tested might interact with these factors is unclear. The authors also pointed out that some of the study took place during the COVID-19 pandemic, and the activities of owners was likely affected by this event. Finally, there was some missing video due to technical issues, and it is unclear if this might have affected treatment or control dogs differently or otherwise influenced the results.

The authors also mention in the paper that, “after the first 40 dogs completed the study, the devices were sent to the manufacturer for testing; devices that were no longer active were removed from the study and replaced.” They never discuss, however, how many devices malfunctioned and needed replacement, which raises the question of how many dogs may have been “treated” with devices that were not actually operating properly. Presumably, this wasn’t mentioned since it was not a common occurrence, but it would have been useful to include this information.

The less good news is that the results were mixed and inconsistent, yet as is usually the case, they were reported as positive. It is common for research studies that measure multiple outcomes for some to show an effect and others not to. It is often recommended to designate one outcome measure as most important in advance and to use only that to decide if the test treatment works. This avoids the problem of having both successful and unsuccessful outcomes and simply having authors emphasize the positive and de-emphasize the negative.

In this study, the subjective owner assessment showed improvement for all dogs and no difference between treatment and placebo. This is a great illustration of the importance of control groups and placebo treatments in veterinary studies. In this case, the owners were as likely to see improvement with no treatment as with the PEMF device. This was probably due to a combination of caregiver placebo effects and the nonspecific impact of being in a clinical study, where patients get more monitoring and treatment than when they are not in a research trial.

The failure to find any difference in this outcome does not necessarily mean the treatment was not effective, but it does indicate that any benefit it may have had was indistinguishable from placebo to the owners. This is critical since it is mostly the owner perception that determines whether a treatment is thought to be working, and whether treatment is changed or a pet is rehomed or euthanized, in the real world of clinical management of SA.

The more objective analysis of video recordings showed mixed results. In terms of negative behaviors, there was no significant effect of treatment overall, and the comparison between the treatment and sham group was not significantly different at 4 weeks but was different at 6 weeks. The difference from baseline was significant for both groups at week 4 and for only the treatment group at week 6. 

In terms of successful treatment, defined as at least a 100% increase in desirable behavior in the video recordings, the treatment group was significantly higher at 4 weeks but not at 6 weeks, and the difference was borderline overall (a p-value of 0.05 is considered statistically significant, and this difference showed a p-value of 0.047). 

These results illustrate the problem with multiple outcomes measures and no clear statement before the study of which is primary or what the expectations are. Based on the questionnaire, one could conclude the treatment didn’t work. This is probably not justified since this is a weak measure of effect, but as I mentioned it does signify that the treatment may be no different from placebo in the perception of owners, which is important for how dogs with SA are ultimately managed.

The more objective video assessment showed no overall difference in negative behaviors, which again is consistent with no meaningful treatment effect. There was a difference at 6 weeks, however, and this could be cited to argue that the treatment took time to have a measurable benefit. Unfortunately, this is inconsistent with the results for positive behaviors, which were better for the treatment group at 4 weeks than at 6 weeks, and which again showed a borderline level of statistical significance that could be interpreted as either a real effect or no real difference from chance.

Finally, the importance of consistency across studies and replication cannot be overemphasized. It has become apparent in the last ten years or so that there is a huge problem in biomedical science generally, and in human behavioral science in particular, with replication. Decisions about the causes and treatment of disease are made on a few studies, or even a single study, and then it turns out those results cannot be reproduced, which strongly suggests they were not accurate in the first place. 

Veterinary medicine has always suffered from a lack of efforts to replicate research studies, as well as from a lack of good studies in the first place, and this makes it very likely that many of our treatments don’t actually work. All studies should be reproducible before widespread adoption of treatments based on their results occurs, and the mixed results of this particular study make it especially important to show that the findings are repeatable.

Bottom Line
This is a well-designed and well-conducted study that shows a mixture of positive and negative results. The most appropriate conclusion would be that the results suggest PEMF might be useful to separation anxiety, but whether or not it is, and how effective it might be, remain to be determined. Given the minimal risks, use of PEMF for this condition is not unreasonable so long as it is not substituted for therapies with better supporting evidence and owners are made aware that the evidence for PEMF is weak and inconclusive. 

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The Bell Tolls for Resveratrol

Only the most dedicated followers of this blog are likely to remember this (are there any?), but way back in 2009, I first wrote about resveratrol in an article about supplements for cognitive dysfunction and brain aging in dogs. My conclusion at that time was:

Resveratrol, in short, stands at the juncture of hope, profit and scientific promise — a social phenomenon galloping ahead of research that is undeniably intriguing but very incomplete.

That was followed by several updates on the status of resveratrol, which still didn’t find scientific justification for the hype.


it is a fine example of both the dangers of excessive and premature commitment to a hypothesis and promotion of products based on it as well as of the ultimately self-correcting nature of the scientific process.


supplementation is probably not justified for most people or for our pets


The bottom line here is that we don’t know for certain, but the compound is looking less promising the more we study it.

Since then, I haven’t spent much time checking the evidence base for this compound, but I suspect it is still quite popular, at least based on the fact that it keeps showing up in products, including my wife’s shampoo!

Once I started working in the aging biology field, I found that the story of resveratrol is even more byzantine and disappointing than I had realized. Dr. Brad Stanfield has recently released this video tracing the history of this molecule in the aging field, and it is an excellent example of one of my signature soapbox issues- the dangers of rushing to commercialize a promising but unproven therapy. Sadly, this is still the norm in veterinary medicine, and I am not optimistic we will learn from this example.

Posted in Herbs and Supplements | 2 Comments

What is a Conflict of Interest?

One of the most common objections I see to my promotion of science-based treatments is that the scientific evidence supporting them is invalid because it is tainted by some association with Big Pharma, Big Kibble, or some other industry bogeyman. This is a convenient objection to any kind of evidence for science-based medicine or against alternative medicine because it uses elements of truth to make an ultimately invalid argument.

Financial bias is a real thing, and it does impact how we should evaluate scientific research. However, conflicts of interest are a lot more complicated than this, and our understanding and interpretation of them needs to be a lot more sophisticated than “industry funded=bulls$#t” Here is my attempt, from my VPN+ column, to take a more nuanced look at this subject.


A key component of evidence-based medicine (EBM), and of modern life, for that matter, is critical appraisal. This means critically evaluating information before accepting or acting on it. In this time of “alternative facts” and widespread harm caused by acceptance of false or misleading information, the core EBM skill of critical appraisal is more important than ever.

In the context of evidence-based veterinary medicine (EBVM), critical appraisal refers specifically to “a formal, unbiased, systematic approach to assessing the quality and relevance of evidence presented in a paper and its applicability to decision making for our patients.”1

As a clinician, before I decide whether to believe the results or conclusions of a published research study, or utilize them in caring for my patients, I have a responsibility to decide for myself how reliable the results are, how likely they are to represent the truth, and whether they are applicable to my patients.

All too often, vets skim the abstract or discussion section of a paper, find the main conclusion, and then take that on faith and use it to guide their practice. Unfortunately, much of what is published in the scientific literature turns out to be more complicated than it first appears, irrelevant to many patients in the world of primary care, or simply wrong. Critical appraisal is the last line of defense between our patients and unsafe or ineffective treatment based on bad information.

There are many aspects of research publications that must be evaluated in the course of a thorough critical reading. The focus of this column is conflict of interest (COI). This is an issue frequently mentioned in guides to critical appraisal, and often used to dismiss the results of published research, but it is an element of critical appraisal that is especially problematic and for which clear guidelines are not available.

What is a conflict of interest?

Even the definition of a COI is challenging and subject to debate.2–4 I find it useful to define a COI broadly as any personal, institutional, or financial relationship that might influence the beliefs, judgements, or actions of an investigator during the design, conduct, analysis, and reporting of scientific research. This helps to distinguish a COI from mere personal belief, but it goes beyond the common and excessively narrow view of COIs as exclusively about financial interests.

A COI is simply one category of bias that can influence the outcome of scientific research. In ordinary use, the term “bias” has negative connotations as it mostly refers to various forms of prejudice or discrimination against groups of people. However, in the parlance of EBM, “bias” simply means any factor that systematically distorts the results of scientific research away from the truth.

If I flip a coin that is unevenly weighted 100 times and get heads 80 percent of the time that is a type of bias. If a researcher chooses only male dogs to study the effects of a drug, that is a type of bias that can lead to a result consistently different from the true effects of the drug on dogs in general. If a researcher has a particular belief that affects how they choose their hypothesis, design their study, analyze the data, and decide whether or not to publish, that is a type of bias, as well.

It should be clear from this definition and examples that bias is ubiquitous in all research. It is not a sign of bad intentions or incompetence; it is an unavoidable consequence of the operation of the human brain and the imperfection of scientific methods. None of us is without bias if we have any beliefs or distinctive individuality at all. The methods of science exist to help compensate for some of the most common and troublesome sources of bias that arise from the operation of the human brain. This is a pretty uncontroversial view in the fields of EBM and the philosophy of science.

I will also make the potentially more controversial claim, however, that none of us is truly free of any conflict of interest either. Science is a community process, rarely conducted in isolation from other people or institutions, and our relationships inevitably affect our beliefs and practices as scientists. Despite the implications of the word “conflict” in conflict of interest, I believe it is useful to think of a COI as simply a type of bias, and as such, morally neutral in most cases. Just as the term bias lacks pejorative connotations in EBM, the term COI should not be seen as implying malfeasance or bad faith.

Of course, deliberate actions to alter or even fabricate scientific data motivated by financial interests, career considerations, or other types of COI relationships are clearly unethical. However, most COI, like other types of bias that trouble scientific research, involves unconscious and unintentional skewing of research results in a direction influenced by our relationships and beliefs. A researcher can be perfectly honest and genuine in attempting to produce objective, reliable data and still have a COI that influences the results of their research.

What constitutes a COI?

The majority of research into COI and how it influences medical research outcomes focuses on financial COI.2,4 If a researcher stands to benefit financially in some way from a certain study outcome, they are considered to have a COI. This may involve financial gain from the success of a product or service being tested, or the effect of research outcomes on the fortunes of a commercial entity, or other institution the researcher is affiliated with.

The classic example of financial COI is research funded by pharmaceutical companies. It has been pretty consistently demonstrated in human biomedical research industry funding of clinical studies is associated with more favorable study outcomes than is funding by government or nonprofit organizations.3,4 There is limited evidence in veterinary medicine, but it seems likely a similar industry funding bias exists in veterinary clinical trials.5

This relationship is often used to dismiss industry-funded research as hopelessly biased, and to suggest there is deliberate manipulation of all such research for financial gain. Such dismissals, not surprisingly, often come from individuals critical of conventional medical treatments and interested in promoting alternatives. However, it is no more accurate or useful to suggest funding bias is simply fraud or it invalidates all research connected with pharmaceutical or other commercial entities than it is to deny such bias exists at all.

Funding bias is a serious problem, especially given the paucity of noncommercial funding sources for veterinary research. However, it is very rarely the case that it manifests as deliberate fabrication or manipulation of data on the part of iindividuals hoping to improve their financial fortunes. Such deliberate cheating would, perversely, be easier to detect and prevent than the real problem, which is unconscious bias embedded in the perspective of researchers, which influences the questions asked, the design and conduct of studies, and the analysis and reporting of results.

Researchers are typically affiliated with institutions; mostly universities or commercial companies. People tend to gravitate toward institutions populated by like-minded individuals with similar views, and we tend to incorporate the views of our close colleagues or mentors into our own perspectives on scientific questions. Similarly, commercial organizations tend to hire researchers and fund research that aligns with their commercial goals.

For example, a scientist interested in the possibility the anti-inflammatory effects of non-steroidal anti-inflammatory drugs (NSAIDs) might suppress the development of cancer is likely to seek work or funding from companies developing such drugs, not from an herbal medicine company that promotes natural remedies as safer than NSAIDs.

Additionally, a nutritionist concerned about the negative health effects of extruded commercial diets isn’t likely to seek or find support for research seeking to identify such harms from a company selling such diets, and they will likely end up working with like-minded researchers and seeking funding from sources with aligned interests.

Finally, a doctoral student in need of mentoring, funding, and help starting a career is very likely to share many of the views of their academic advisors, at the end of their training at least, even if not at the beginning.

These are all examples of the natural alignment of views that tends to occur when people join together in institutions to participate in scientific research. Funding bias, like other forms of COI, is more likely to be an expression of the shared perspectives of individuals grouped in institutions than simple fraud. This does not, of course, mean it is not a serious problem that skews research results away from the truth. The fact commercial organizations choose what research to conduct or support, and influence the way that research is designed, conducted, and reported, can lead to a body of evidence significantly mistaken or misleading even without any fraudulent intentions or actions.

However, it is worth noting the same type of alignment of views, leading to systematically biased research results, can occur when the alignment is fostered by ideological, political, cultural, and other nonfinancial factors. Research supported by pharmaceutical companies is more likely to be favorable to their products than independently funded studies, but research on homeopathy conducted by homeopaths and published in alternative medicine journals is also much more likely than not to be positive.6,7 Studies of acupuncture conducted in China, where the practice is widely embraced by the populace and the government, are much less likely to report negative results than acupuncture studies from countries where the practice is not part of the shared cultural and political history.8–10

While financial incentives and commercial relationships form an important type of COI, we must recognize the problem of COI is seldom simplistically reducible to deliberate skewing of results in the interest of making money. The ways in which we identify and mitigate COI and incorporate it into our critical appraisal will be different, and more effective, if we take the broader view of COI as involving the influence of personal and institutional relationships on belief and judgement rather than simply following the money.

How does a COI bias research?

When viewed in this larger frame, conflicts of interest can be identified as the potential influences of institutional and personal relationships on research results at every stage of the scientific process. Which questions we choose to ask as scientists and how we go about answering them are related to our context and relationships.

As a general practitioner, for example, I have investigated factors influencing the risk of complications from routine neutering surgeries at my practice because this was a relevant subject for me and my colleagues in a way it likely would not be for an academic surgeon. My study was conducted as a clinical audit, not a randomized controlled trial, because it was part of an in-house quality improvement process at my hospital, not an academic research project. The data collection tools (simple questionnaires) reflected the practical realities and interests of the doctors participating in the study. The examination of how various types of suture material might influence complication rates included only those types of suture we use at our practice, and the neutering techniques compared were those our doctors used, even though there are other materials and techniques we could have considered. These and 100 other choices made during the research project reflected bias associated with my personal and institutional relationships.

One might be tempted to argue this isn’t truly an example of a COI. Given the emphasis on financial incentives in discussions of conflict of interest, one could claim there is not a COI for me to disclose if I publish the results of my study because I don’t have an obvious financial stake in the outcome.

Of course, one could imagine a possible financial or personal incentive. Perhaps clients would stop choosing to have their pets neutered at my practice if we reported a high rate of complications? Perhaps my boss would penalize doctors with higher complication rates, and I might be tempted to adjust my findings depending on my relationship with my colleagues?

However, my point is such narrow personal motives are only a limited subset of the ways in which our personal and professional affiliations influence our scientific research efforts, and excessive focus on these types of influences leads us to overlook other important and relevant factors.

I suspect the types of COI-related bias found in research conducted at commercial and academic institutions resembles this example more than the cliché of shadowy figures in industry deliberately manipulating or hiding data to make their companies’ products look good. I have no doubt that happens, of course, but it is far less common than a subtle, creeping bias introduced by a thousand small choices made in an environment where most people have the same perspective and beliefs.

Regular readers will know, of course, in the last year I have begun working in a biotechnology company developing drugs to extend lifespan and healthspan in dogs. Is this a conflict of interest in terms of writing about COI? Sure! Of course, I work for a company with an exemplary ethical and scientific culture, and I wouldn’t have taken the job if I didn’t believe this to be true. And part of my job there is to be the nagging voice of our collective conscience and push for the best possible science within the constraints of regulations, funding, and the ultimate goal of developing successful clinical therapies. However, my perspective is absolutely influenced by the context in which I work and the ethos of my work community.

I have seen how the regulatory and economic framework of a biotech startup differ from the clinical and academic research contexts. The questions we ask, how we frame them, the studies we design to answer them, and how we handle data collection and analysis are all influenced by this context, just as my research in private practice and the research of any university veterinarian is influenced by those environments and relationships. That is why I rush to disclose this relationship any time I talk or write about any scientific subject.

The interesting and important question, then, is not whether a COI exists for a given research project, since it almost inevitably does, but what do we do about it?

How should COI be considered in critical appraisal?

In the past, a potential COI was largely ignored, with the lofty assumption that because scientists had integrity, their work would not be influenced by such relationships. As I’ve already argued, I believe we are all influenced by our relationships in subtle ways against which good intentions are not an effective defense. This has become difficult enough to deny that it is now more common for a COI to be handled through disclosure. Journals, funding bodies, regulators, and others with some authority over scientific work typically require scientists to disclose any potential COI relationships (e.gJAVMA,JVIMJVECCJAAHA). Such disclosure is voluntary and typically limited to financial COIs, which is problematic, but at least it is easier now to know when such relationships exist.

Sometimes journals take failure to disclose potential COI seriously. The Journal of Veterinary Internal Medicine recently retracted a paperbecause the authors failed to disclose an obvious financial COI. On the other hand, I wrote last Octoberabout an undisclosed COI that could have potentially significant relevance for interpretation of a narrative review, and in that case the journal chose to largely ignore the omission when it was pointed out by readers.

The difficult question for the critical consumer of science, however, is what to do with information about COIs when it is disclosed. The sad reality is most often disclosed COIs are ignored entirely (if we agree with the conclusions of the research or share the general perspective of the authors, or simply because we don’t believe “good scientists” can be biased11), or used as a pretext to completely discount the results (if we disagree with the conclusions or have a conflicting perspective on the issues).

To again pick on the extreme case of homeopathy, homeopaths accept the shoddiest and most obviously biased studies as probative when they show efficacy for homeopathy, and they reject any research conducted or conducted by science-based investigators or funded by any kind of entity other than a homeopathy manufacturer.6 (Not surprisingly, of course, I have been accused of exhibiting the same type of bias in reverse, which is fair, though I think the record of my public critical appraisal of research studies of all kinds over the years doesn’t support this claim). Sadly, veterinary students who should know better react in a similar way, discounting their potential susceptibility to bias from associations with the pharmaceutical industry.11

Veterinarians who want to read research studies critically are justly confused about how to incorporate CI into their assessment, and there are few resources available to help them12,13. My perspective is a lot of the problem stems from our view of research evidence as binary. We believe a study either proves or disproves the hypothesis it is testing; a drug either works or doesn’t work; a proposed etiology either does or does not cause a disorder. We think the results must be black or white, and we further believe we can make such judgements for every single study independently. These beliefs are mistaken and inconsistent with how science really functions.

A more useful approach to integrating COI into critical appraisal, and into our overall assessment of what is true and false in medicine, is a philosophically Bayesian manner. Though the mathematic details of Bayesian analysis are complex, the underlying principles are straightforward14,15. They suggest that we should assess the reliability of evidence and conclusions in a research study as follows:

  1. Establish a likelihood of the hypothesis or claim being true or false based on what we already known.
  2. Evaluate the data presented and assess all the usual strengths and weaknesses.
  3. Shift our estimate of the likelihood the hypothesis or claim is true to a degree proportional to the strength of the evidence in the paper.

This is really much simpler than even this stripped down description. It just means COI is only one factor in our overall weighting of the evidence in a given study, and each study is only one bit of evidence in our overall assessment of every claim or hypothesis. There is a continuum of confidence in both the study results and their meaning for our beliefs about whatever subject they address, not a binary state of true or false, pure or biased.

When I read a paper on, for example, a new drug, and I see it was funded by the company making the drug, this reduces my confidence in the conclusions slightly (especially if the conclusions are favorable to the company’s interests). However, if the study was conducted by independent researchers insulated from direct influence by company employees, and if the bias control methods are rigorous, that COI has a pretty small impact on my confidence in the study. In contrast, if the study was conducted in a company facility by company employees using subjective outcome measures and with poor methodological control for bias, the COI will significantly undermine my confidence in any positive results.

The details of how we evaluate the significance of potential COI will vary with the specific research project. The important takeaway here is we shouldn’t use COI as a sole reason to accept or reject evidence. We should consider potential COI in light of both the design and conduct of the specific study, and the potential for researcher bias based on the larger context.

A good example is a recent study of the influence of diet during puppyhood on the risk of canine atopic dermatitis (CAD) developing later in life, which appeared in JVIM. I have written a detailed critical appraisal of this study in my regular Veterinary Practice News column, and contributed to a letter to the editor of JVIM detailing various concerns about the paper.

The paper ultimately concludes, with some caveats, feeding raw diets to puppies may protect them against developing CAD as adults. The authors declared no COI. As required by JVIM, they did declare sources of funding. These included both manufacturers of raw diets and Joseph Mercola, an infamous proponent of raw diets and alternative medicine and an anti-vaccine activist repeatedly warned by the Food and Drug Administration (FDA) for promoting COVID-19 misinformation and selling unproven treatments.16,17

The research group, furthermore, has an established history of publishing research promoting raw diets and claiming detrimental health effects from conventional commercial diets. The senior author, an academic researcher with some minor ties to commercial pet food companies, has specifically identified financial COI as a problem in raw diet research, saying, “[raw food is] not really researched in universities. Most universities get sponsored by these big billion-dollar companies, and you don’t really want to step on their toes, I guess. But, I think that’s not really ethical.”18

This is a great example of what I would consider a COI that does not involve direct financial interests or any intentional malfeasance. The researchers have personal and professional affiliations with individuals and institutions committed to the hypothesis raw diets are beneficial and conventional pet foods are harmful. They are undoubtedly experienced and ethical scientists, and they are unlikely to reap any significant financial gains from promoting this idea. Yet, in the context of their history, and the specific work in this study, their affiliations still amount to a COI that must be considered in weighing the reliability of the evidence they provide.

The bottom line

The more interesting I find a subject, the more I write. Not a great habit in today’s TL;DR culture! (That’s “too long, didn’t read.”)

  1. Conflicts of interest are not just about money! All personal, financial, and institutional relationships influence our perspective in ways that can bias the research we do.
  2. Everyone has some type of conflict of interest. Being smart and ethical doesn’t prevent this from influencing the research we do.
  3. Every possible conflict of interest should be reported when we publish scientific research.
  4. Conflict of interest alone does not justify uncritical rejection of scientific evidence.
  5. We should weigh the significance of possible conflicts of interest in the context of the potential for bias to influence study results and the efficacy of bias control methods employed in the study.
  6. No single study ever proves or disproves anything (OK, maybe once in a while, but not often!).
  7. We should assess individual studies and the overall evidence for or against specific ideas in a Bayesian manner, on a continuum of confidence, not with a binary true or false scheme.


  1. Pinchbeck GL, Archer DC. How to critically appraise a paper. Equine Vet Educ. 2020;32(2):104-109.
  2. Johnson C. Conflict of Interest in Scientific Publications: A Historical Review and Update. J Manipulative Physiol Ther. 2010;33(2):81-86.
  3. Mandrioli D, Kearns CE, Bero LA. Relationship between research outcomes and risk of bias, study sponsorship, and author financial conflicts of interest in reviews of the effects of artificially sweetened beverages on weight outcomes: A systematic review of reviews. PLoS One. 2016;11(9).
  4. Institute of Medicine (US) Committee on Conflict of, Interest in Medical Research, Educationand P. Committee on Conflict of Interest in Medical Research, Education, and Practice. Washington, D.C.: National Academies Press (US); 2009. Accessed January 9, 2022.
  5. Wareham KJ, Hyde RM, Grindlay D, Brennan ML, Dean RS. Sponsorship bias and quality of randomised controlled trials in veterinary medicine. BMC Vet Res. 2017;13(1):234. 9
  6. Cukaci C, Freissmuth M, Mann C, Marti J, Sperl V. Against all odds—the persistent popularity of homeopathy. Wien Klin Wochenschr. 2020;132(9-10):232-242.
  7. Ernst E. A systematic review of systematic reviews of homeopathy. Br J Clin Pharmacol. 2002;54(6):577-582. Accessed November 12, 2018.
  8. Vickers A, Goyal N, Harland R, Rees R. Do certain countries produce only positive results? A systematic review of controlled trials. Control Clin Trials. 1998;19(2):159-166.
  9. Ma B, Qi G, Lin X, et al. Epidemiology, Quality, and Reporting Characteristics of Systematic Reviews of Acupuncture Interventions Published in Chinese Journals. J Altern Complement Med. 2012;18(9):813-817.
  10. Wang Y, Wang L, Chai Q, Liu J. Positive results in randomized controlled trials on acupuncture published in chinese journals: a systematic literature review. J Altern Complement Med. 2014;20(5):A129. Accessed November 14, 2018.
  11. Dowers KL, Schoenfeld-Tacher RM, Hellyer PW, Kogan LR. Corporate Influence and Conflicts of Interest: Assessment of Veterinary Medical Curricular Changes and Student Perceptions. J Vet Med Educ. 2015;42(1):1-10.
  12. Lundh A, Boutron I, Stewart L, Hróbjartsson A. What to do with a clinical trial with conflicts of interest. BMJ evidence-based Med. 2020;25(5):157-158.
  13. Resnik DB, Elliott KC. Taking financial relationships into account when assessing research. Account Res. 2013;20(3):184-205.
  14. Homwong N, Hunprasit V, Marthaler D, et al. A Bayesian approach for inductive reasoning to clinical veterinary medicine: The math of experience. J Vet Med Anim Heal. 2015;7(10):308-316.
  15. Gardner IA. The utility of Bayes’ theorem and Bayesian inference in veterinary clinical practice and research. Aust Vet J. 2002;80(12):758-761.
  16. Satija N, Sun L. A major funder of the anti-vaccine movement has made millions selling natural health products. Washington Post. December 20, 2019.
  17. Alliance for Science. FDA warns Mercola: Stop selling fake COVID remedies and cures.
  18. Habib R, Becker K. The Dog Cancer Series: Rethinking the Cancer Epidemic Vol. 1, Chapter 4 (Transcript). 2018:73.
Posted in General, Science-Based Veterinary Medicine | 3 Comments

SkeptVet EBVM Column Makes VPN Top Ten List

My monthly evidence-based medicine column for Veterinary Practice News took the top two spots in this year’s list of top ten feature articles! You can find links to all of my columns right here.

Posted in Presentations, Lectures, Publications & Interviews | 3 Comments

What are General Practice Vets Good For?

From VPN+

“We must provide an outlet for the creative faculties…And it is this challenge which is recognized by every graduate who turns away from practice, disillusioned by his or her inability to find satisfaction in a situation where…the expectations of training are dashed by the reality of practice. Somehow, we must change the system lest the process of education leads to an increasing number of square pegs looking for a home in a world of round holes…

“We must seek to elevate the status of the practitioner, not only that his position is elevated in the eyes of the academic but, more importantly, in the minds of practitioners themselves. Too often we hear that a practitioner cannot be expected to teach or to research. This is the philosophy of despair.”1

~Peter Rossdale1

If I’m being honest, the first couple years of veterinary school were a bit tedious. I was a career-change student, about 10 years older than most of my classmates. I had behind me years of struggling to find a career that was meaningful and challenging, yet also economically viable. In that context, being back in school wasn’t such a bad thing. And unlike a lot of my classmates, I hadn’t always dreamed of being a vet, so I didn’t experience the shock of achieving a lifelong dream only to find it was, like reality so often turns out to be, imperfect. However, hours and hours spent memorizing facts, many of which I suspected I would never need again (and I was right!), wasn’t exactly thrilling. I did ok, but I didn’t stand out until I got to clinics.

When I started my clinic rotations, everything came to life for me. The process of clinical reasoning, of collecting and sifting through the information available to find the salient patterns, and then matching that to the tools I had to help my patients, was fascinating and satisfying. Doing medicine was enormously better than learning about it! I may not have been the smartest or most talented in my class, but I turned out to be pretty good at the clinical aspects of veterinary medicine, and my teachers noticed.

One day, an internal medicine resident came up to me while I was studying in a hospital hallway. She wanted to tell me she and some of the other residents and faculty members running the rotation had been talking about me. They had concluded I absolutely had to do a residency because, in her words, “You’re too smart for general practice.”

Of course, my first reaction was an ego-driven flood of dopamine and self-satisfaction. I appreciated the complement, and it reinforced my suspicion I was actually pretty good at this stuff. Alas ,when I had some time to think a bit more about the remark, I started to take a darker view of it.

I haven’t found a definitive source of data, but using numbers from the American Veterinary Medical Association (AVMA) and the Bureau of Labor Statistics, it seems about 20 percent of veterinarians are board-certified specialists. That number was surely lower when I graduated 20 years ago! In this context, one view of the resident’s compliment could be specialty practice is for the best and brightest, and the rest of us have to settle for the less intellectually challenging life of primary care medicine. Being a GP, in this frame, is a consolation prize or a fallback position for the majority of us who don’t make the cut.

By temperament I’m certainly a nerd, and I likely would have pursued a specialty certification (probably in emergency and critical care) and an academic career if that had been possible. However, at the time I graduated, I was 35 years old, I had a six-month-old daughter and a spouse who had indulged my search for a career long enough. I also had $160,000 in loan debt (a pittance by today’s standards, of course, but easily in the top three percent of vet school debt back then). Internship and residency weren’t realistic, and it was time to get a job.

GP life begins

So, did I settle for a lifetime of routine and drudgery? Nothing but vaccines, spays and neuters, and anal glands until I retired? Or maybe, at best, the challenge of entrepreneurship and running a small business? Am I the old guy who hasn’t added a new procedure, drug, or piece of equipment to his toolbox since most new grads were born and doesn’t see why the way we did things in the “good old days” needs to change? Well, not exactly…

I have found many ways to sustain my engagement and enthusiasm with medicine, to challenge myself and grow, both professionally and personally, in my work. Most importantly, I have maintained a commitment to high-quality, evidence-based medicine (EBM), and I have been able to help my patients and clients, and even contribute to the growth of the veterinary profession—all as a lowly GP. So how did I do that?

To start with, when my first practice didn’t meet my expectations for quality of care or opportunities to learn, I started doing relief work at local emergency hospitals to take on more challenging cases. In the absence of a mentor willing and able to teach me, I looked for every opportunity to learn the hard way. It was pretty scary being on alone at night right out of vet school. It wasn’t how I would have chosen to learn, but such a sink-or-swim approach seemed all that was available to vets not destined for internships and residencies in those days.

Once I had a few years in practice, I managed to talk my way into an exceptional hospital, which I have long considered a model of what is possible in general practice. We have been an independent 24/7 practice with up to 30 veterinarians, almost all GPs, and many extremely talented technicians, including some with VTS certification. Management always supported individual veterinarians in pursuing their interests, which allowed me to offer abdominal ultrasound and echocardiography, endoscopy, chemotherapy, and a high-level of surgical and medical care to my patients.

While working in this rich environment, I have constantly striven to “up my game.” I got involved in the Evidence-based Veterinary Medicine Association (EBVMA), helping to lead this organization made up largely of academic veterinarians. I have published and spoken on evidence-based medicine and promoted it to primary practice clinicians around the world.

I have also been lucky enough to have the opportunity to teach veterinary students in practice. Many come to clinics with a wealth of facts crammed into their heads and little idea how to organize and use them effectively to help patients. As much detailed content knowledge as they get from each specialist they train with, many students get very little process knowledge.

Clinical reasoning skills, the ability to take all the knowledge they have ingested over the years, and both organize and use it effectively to make decisions in real time across a broad set of medical domains and patient populations, is something few veterinary students I see have had the chance to think deeply about or practice. This is one area in which the general practitioner is preeminent; the pragmatic evaluation of available information and application of available resources to solve clinical problems within the inevitable constraints of time and money. The broader the range of problems you have to solve and the more limited your tools for solving them, the more efficiently and creatively you have to think!

I have also continued my formal education, completing a master’s degree in epidemiology. Even at this stage (don’t you dare say “venerable!”) of my life and career, I am seizing opportunities to learn and grow. I have shifted to part-time clinical practice so I can take on a role in canine aging biology research. I still do spays and neuters, vaccines ,and anal glands, but that is hardly a fair summary of my career as a GP.

Of course, my path isn’t the right or the only way to make life in primary care practice meaningful and challenging. It is just one example of many possible paths. Yet, I think it belies the notion academic veterinarians all too often inculcate in their students that being a GP is a dead end, a second class of veterinary career.

I still run into this view from time to time. When doing an advanced echocardiography training course, I was chastised for even thinking I should be able to offer this service by the other students (all internists). A few specialists have been offended when I questioned their recommendations, even when I could present clear research evidence to support my concerns, and their position relied entirely on their clinical experience and authority as diplomates. And the medicine resident who encouraged me to pursue specialization so many years ago was not the last to suggest, with the best intentions, my knowledge and abilities were somehow inconsistent with my role as a GP. I doubt I am the only primary care veterinarian to have such experiences.

How to accurately envision general practice

So, how should we think about the role of GP? How should we see ourselves fitting into the profession, and how should students and academics learn to understand our role? What strengths and limitations characterize the general practice role, and how do these complement the academic and other veterinary roles? All of these are deep and hard questions with no simple answers, but I will offer a few thoughts.

Given primary care practice is where the vast majority of patient care happens, our profession has an ethical responsibility to prepare GPs for providing high-quality, evidence-based care. Many of the students I teach and the new graduates I mentor seem to come out of the veterinary educational system with the idea they should handle only minor problems and refer anything challenging.

The definition of what is appropriate for GPs to manage seems to shrink yearly. It’s not just the shock I still sometimes see when I talk about performing an echo or an endoscopy in primary practice. I have had new graduates who felt it was inappropriate to interpret a radiograph or diagnose a mast cell tumor on cytology without specialist input. The message they often seem to get from their teachers (nearly always academic specialists) is that if a specialist can do something then a GP shouldn’t do it.

Of course, this extreme view is not consistent with practical and economic reality. The obvious problem of insufficient specialty capacity and the inability of many pet owners to afford the cost of specialty care is an obvious flaw in this model. However, I believe there are other flaws to this view that are more grave.

One is that such “dumbing down” of general practice to routine wellness care and management of only minor health problems diminishes the quality of care patients receive. It creates a self-fulfilling prophecy. If we teach veterinary students that talent, intelligence, and ambition can only be satisfied in specialty practice, then people with those attributes will eschew general practice. If we don’t teach GPs that they should be practicing high-quality, EBVM because only specialists can do that, then it will become true.

Another problem with primary practitioners gradually ceding diagnosis and treatment of serious problems to specialists should be abundantly clear from even a casual glance at the human healthcare system. The hyperspecialization of human medicine has led to absurdities.

I once started explaining the nature and management of a cranial cruciate ligament rupture to a client when he stopped me with a chuckle. He was an orthopedic surgeon. After four years of undergraduate education, four years of medical school, an internship, and more than one residency, his entire career consisted of six procedures on the human knee. A brilliant, and arguably overeducated man, had been reduced to a highly paid, very specialized carpenter.

Is this the model we wish veterinary medicine to follow? Laying aside the economic realities that would impede full adoption of the hyperspecialization, is this even a model we should aspire to? I would argue it is not, yet that is the direction we would head in if the lessons many of my students and new graduates take away from their training were implemented.

Advantages GPs possess

The strengths of the primary care practitioner are many. We have a holistic view of the patient throughout the lifecycle that is usually unavailable to the specialist. While our knowledge base is inevitably shallower than those in specialty practice, it is broader, allowing us to integrate multiple medical conditions, husbandry, and other owner variables, individual temperament, life stage, and many other factors into the management of specific healthcare problems. I would argue this approach typically allows for better overall patient care, especially when cases are complex with multiple concurrent morbidities.

GPs are also consummate problem solvers, accustomed to making do with limited information and resources. If this ability is not only honed by experience, but strengthened by the application of evidence-based medicine techniques and training in clinical reasoning, it becomes a powerful tool. Specialists are undoubtedly knowledgeable, talented, and creative thinkers, but depth of expertise comes at a price; the loss of a broad perspective and a tendency to follow familiar patterns within a domain even if elements of the context outside of that domain might suggest a different approach.

Finally, there is the obvious issue of accessibility and affordability I have already mentioned. Too many companion animals already go without care because their owners cannot afford it.2 Increasing the reliance on specialists without a fundamental shift in the economic model of veterinary medicine will simply make care less available to more patients.

Apart from the benefits to patients and clients in supporting high-quality care in general practice, encouraging GPs to value themselves and their work, and to stretch themselves professionally, is important to maintaining a talented and satisfied veterinary workforce. We all know our profession is struggling right now, with vets bearing the stacked burdens of high workloads, huge debt, and the many physical and emotional challenges of the job. Constraining people to smaller, and smaller boxes, as GPs or as specialists, is just creating more round holes for Dr. Rossdale’s square pegs. Channeling the most ambitious and talented students into specialty practice or academia, and denying those who do go into general practice the opportunity to fully engage their intellect and creativity in their work can only exacerbate the problems our profession is facing with burnout and job dissatisfaction.

How, then, can we encourage all of our students and new veterinarians to maximize their potential, provide the best possible care for our patients, and avoid the pitfalls of hyperspecialization that bedevil our colleagues in human medicine? As I have already implied, I think evidence-based medicine is a key part of the answer!

Teaching all veterinarians, regardless of their eventual area of practice, to practice EBM would be a good start. While some effort to do this is already part of the curriculum, I cannot say most of the students or new graduates I see have really absorbed the core concepts of critical thinking and reasoning that underlie EBM. We are still emphasizing memorization and regurgitation of facts over rational, effective reasoning strategies.

My students are better able to search the literature and use electronic information tools than my generation, but they don’t often seem to understand what these tools are for. They still seem to rely primarily on authority and the dicta of their mentors for guidance rather than using the information they have learned to support critical reasoning. When I question the rationale for a particular treatment choice, all too often the response is still, “That’s what Dr. X said to do.”

Teaching veterinarians to think critically and independently, and to rely on critical appraisal of controlled evidence when possible, can only improve the quality of clinical reasoning and patient care. It also has the advantages of strengthening one’s confidence in one’s recommendations and practices, and reducing the tendency to defer to academics or specialists, which drives a lot of the relinquishing of cases and problems that could appropriately be retained in the general practice setting.

EBM also helps to delineate the role of generalist and specialists. In areas where there is strong evidence to guide diagnosis, prognosis, and management, there is less need for the deep and narrow knowledge and experience of the specialist. Conversely, when a problem is uncommon or not well understood, and there is little reliable evidence concerning it, a specialist’s strengths become critical.

As an example, the vast majority of the heart disease cases I see in practice are myxomatous mitral valve disease (MMVD). This is a relatively well-understood condition with clear diagnostic and staging criteria, and strong consensus guidelines available to inform treatment. I use echocardiography to support my management of MMVD cases. In my career, I have done a few over 1,000 echocardiograms, and about 85 percent of these have been MMVD cases. There is no reason why the greater expertise and experience of a cardiologist should be necessary to diagnose, stage, and manage this condition in most patients with typical presentations.

My use of this tool fits well into the role and competency of the general practitioner. And the skills I have developed evaluating MMVD patients have helped me utilize the tool in other ways that improve patient care. I don’t need to call in a cardiologist to identify a right atrial mass prior to subjecting a patient with hemangiosarcoma to a splenectomy. I can identify and manage pericardial effusion without the delay of waiting for a specialist or transferring the case. All of these are reasonable and natural elements to primary care.

On the other hand, there are absolutely cardiac cases that fall outside my competency that I should, and do, refer. I don’t ultrasound young animals with murmurs because many will have uncommon congenital anomalies I am not qualified to identify or manage. And whenever there is a case that does not fit well into a clear and evidence-based diagnostic pattern, or when I find something I have not seen before, I don’t charge the client for my scan and I call in a specialist who is better equipped to evaluate and handle the case.

Maximizing the potential of GPs does not mean disdaining specialists or not referring cases when appropriate. It means delineating the domains of the two rationally rather than by tradition or by organ system. EBM is a useful way to support primary care practitioners in developing their knowledge and skills, maintaining their job satisfaction, and providing high-quality care while also utilizing specialty and academic services when these are necessary and will benefit the patient.

Of course, even I recognize EBM can’t solve all of our problems. The lessons my students and new graduates are absorbing about their place in the profession are predominantly cultural lessons, expectations of the whole community as envisioned by a small subset of the profession. Academics don’t complain to their students about the failings and misjudgments of GPs because they are mean people. They do so because they see a skewed sample of cases that end up at the university. The most unusual, most difficult problems and those that have not been solved by primary care practitioners are most of the cases that make it to the teaching hospitals. All the cases we manage successfully, often within strict constraints of money and other resources, are invisible to those who teach students how to view the general practice role.

As a profession, we have to think deeply about how we understand the categories of general practitioner, specialist, and academic. If we want to avoid the excessive costs and harm to patient care that have come from hyperspecialization in human medicine, and if we want to provide satisfying and challenging careers for all new veterinarians, we need to avoid the trap of seeing academia and specialty practice as the brass ring and primary care as a consolation prize.


  1. Rossdale PD. Combining research with veterinary practice. Can Vet J. 1978;19(12):327. Accessed July 29, 2021.
  2. Stull JW, Shelby JA, Bonnett BN, et al. Barriers and next steps to providing a spectrum of effective health care to companion animals. J Am Vet Med Assoc. 2018;253(11):1386-1389. doi:10.2460/javma.253.11.1386
Posted in General | 4 Comments

Fresh Diets for Pets: Are they Healthier than Kibble or Canned?

Nutrition is one of the most frequent subjects my clients want to discuss, and often one of the most controversial. Raw diets,1 vegetarian or vegan pet foods,2 ketogenic diets for pets,3 the significance of “artificial” versus “natural” pet food ingredients,4 and the fundamental question of whether veterinarians are trusted counselors when it comes to nutrition are just some of the controversies in pet nutrition I have covered in Veterinary Practice News. 

These are all tough issues, both because of the passionate opinions they engender and because of the inevitably limited and imperfect scientific evidence available to adjudicate them. A key tenet of evidence-based medicine, however, is that we have to make judgments based on the evidence we have, not the evidence we wish we had. Another core principle is that our confidence in any judgment we make should only be as strong as the evidence allows. 

Today’s topic is one where claims and passions far exceed the available evidence—fresh pet food. Various terms are used to describe such diets, including fresh, lightly-cooked, whole-food, etc., and there is no standardized terminology for these diets. I will mostly use “fresh food” as a shorthand for the myriad diets marketed in this way.

In addition to homemade fresh diets prepared by individual dog owners, a number of companies are now selling cooked commercial diets that are designed and packaged like fresh, homemade foods rather than extruded kibble or traditional canned pet food. These companies market such diets with implicit, or often explicit, claims that they are healthier than traditional commercial foods. 

In an extreme example, the founders of Just Food for Dogs (JFFD) have written a polemical book titled “Big Kibble: The Hidden Dangers of the Pet Food Industry” to promote their alternative to traditional commercial diets. They have not been restrained or respectful in their response to criticism of their claims and marketing methods. The company explicitly claims their product is healthier that traditional kibble, and the leaders are not impressed by calls for evidence to prove this: “The mainstream veterinarian needs research and proof that real food is healthier, and that just boggles my mind,” Dr. Chavez adds. “We’re the last healthcare profession that is recommending an ultra-processed daily sustenance. It’s just crazy.”

So, is it crazy to wonder if fresh foods really are healthier than canned or kibble? Can we assume that dogs eating traditional commercial diets will have shorter lives and more health problems than dogs eating fresh diets? Regular readers of this column will already know my answer—nope! Equally “obvious” claims about the complicated relationship between environmental factors and health outcomes have been stunningly wrong many times in the history of human and veterinary medicine, and we should place very little confidence such beliefs without scientific evidence.

The ideal evidence for these claims, of course, would be long-term comparative feeding studies showing dogs eating fresh diets live longer and experience less disease than those eating kibble or canned foods. Such studies would be extremely complex and expensive to run, and I don’t see much chance companies on either side of the debate will step up to support them. This means that, as usual, we need to rely on less robust evidence (and proportion our confidence accordingly).

There is certainly epidemiologic evidence that consumption of whole foods, particularly fruits and vegetables, is associated with improved health outcomes in people compared with packaged and convenience foods. But it needs to be emphasized that commercial dog food is not the nutritional equivalent of potato chips just because both come in bags. Human snack and convenience foods are deliberately designed to be appealing, not nutritious. Pet foods are formulated with much more emphasis on nutritional value, and have been used and evaluated extensively for decades for their impact on health. They may well not be the optimal food we should be feeding, but they are hardly the egregious poison their detractors claim. And as the analogy breaks down, so does the relevance of the epidemiologic evidence in humans to pet feeding practices.

There is little direct research on the potential health impact of fresh diets compared with other cooked pet foods. There is research showing that homemade diets are often nutritionally unbalanced and incomplete, but little evidence pertaining to commercial cooked fresh diets.5–10

A small study was reported as a poster at the 2014 American Academy of Veterinary Nutrition Research Symposium, and this is often cited by fresh food advocates as positive evidence for their claims. Twenty-one dogs of various breeds were transitioned from kibble to a frozen cooked fresh-food diet and basic bloodwork and exams were conducted at the beginning of feeding the diet and again at 6 months and twelve months later. This was a pilot study, so there was no control group, no blinding, no pre-specified outcomes or hypotheses, no reported accounting for repeated measures or multiple comparisons in the statistical analysis, no discussion of any other aspects of the dogs’ health or environment, and overall no significant control for bias or random error. This limitation is especially relevant given that the lead author is Chief Medical Officer for JFFD and also an author of the book I mentioned earlier.

A few differences were found in some clinical laboratory measures before and after the transition to the JFFD diet. Increases were seen in red blood cell count and globulins, for example, though all values remained within reference intervals for all dogs. This sort of data might suggest hypotheses for future testing, but it doesn’t support any specific conclusions about the relative merits or health effects of different types of diet. It certainly does not support the claims in a JFFD press release that their foods “could benefit immune health” and that if the purported trends in the blood values continue for a lifetime “we may see a decrease in chronic diseases such as cancer, renal failure, kidney disease, inflammatory bowel disease, dental disease, etc.” 

There is some laboratory research showing fresh diets have higher digestibility than extruded pet foods, and there may be effects on gut flora and other physiologic parameters.11–14 However, these are, once again, only useful bits of data that suggest testable hypotheses, not conclusive evidence for real-world health effects.  

Personally, I am sympathetic to the hypothesis that pet diet which contain less processed whole ingredients may be superior to conventional canned or extruded dry diets in terms of health outcomes. The epidemiologic evidence in humans, and pre-clinical research in laboratory animal models is suggestive, though by no means conclusive. There are, of course, other issues besides health impacts that must be considered in comparing the merits of different types of pet food. The affordability and accessibility of different diets, storage and stability, safety, environmental sustainability, and many other factors are relevant as well to the recommendations of veterinarians and the feeding choices of dog owners.

The bottom line, as always, is that we should make decisions based on the best possible evidence, and we should limit our claims and confidence to what the evidence can support. Currently, the most optimistic assessment of diets identified by marketing materials as fresh, lightly-cooked, whole-food, human-grade, etc. is that it is plausible they may have health benefits if properly formulated by veterinary nutritionists and properly handled and fed by owners. Biologic plausibility and pre-clinical evidence are necessary starting points, but evidence from the real world on meaningful health outcomes will be needed before we can have any confidence in claims about the benefits of such diets.


1.        McKenzie BA. Debating Raw Diets. Vet Pract News. January 2019:30-31.

2.        McKenzie B. Are Vegan of Vegetarian Diets Good for Pets? Vet Pract News. July 2019:26-27.

3.        McKenzie BA. Is Keto Kind to Pets? Vet Pract News. January 2020:30-31.

4.        McKenzie B. Is banning “artificial” ingredients based on fear or science? Vet Pract News. March 2019:36-37.

5.        Lauten S, Smith T, Kirk C. Computer analysis of nutrient sufficiency of published home-cooked diets for dogs and cats [abstract]. J Vet Intern Med. 2005;19(3):476-477.

6.        Heinze CR, Gomez FC, Freeman LM. Assessment of commercial diets and recipes for home-prepared diets recommended for dogs with cancer. J Am Vet Med Assoc. 2012;241(11):1453-1460. doi:10.2460/javma.241.11.1453

7.        Larsen JA, Parks EM, Heinze CR, Fascetti AJ. Evaluation of recipes for home-prepared diets for dogs and cats with chronic kidney disease. J Am Vet Med Assoc. 2012;240(5):532-538. doi:10.2460/javma.240.5.532

8.        Taylor MB, Geiger DA, Saker KE, Larson MM. Diffuse osteopenia and myelopathy in a puppy fed a diet composed of an organic premix and raw ground beef. J Am Vet Med Assoc. 2009;234(8):1041-1048. doi:10.2460/javma.234.8.1041

9.        ROUDEBUSH P, COWELL CS. Results of a Hypoallergenic Diet Survey of Veterinarians in North America with a Nutritional Evaluation of Homemade Diet Prescriptions. Vet Dermatol. 1992;3(1):23-28. doi:10.1111/j.1365-3164.1992.tb00139.x

10.      Pedrinelli V, Gomes M de OS, Carciofi AC. Analysis of recipes of home-prepared diets for dogs and cats published in Portuguese. J Nutr Sci. 2017;6:e33. doi:10.1017/jns.2017.31

11.      Oba PM, Utterback PL, Parsons CM, Swanson KS. True nutrient and amino acid digestibility of dog foods made with human-grade ingredients using the precision-fed cecectomized rooster assay1. Transl Anim Sci. 2020;4(1):442-451. doi:10.1093/tas/txz175

12.      Do S, Phungviwatnikul T, de Godoy MRC, Swanson KS. Nutrient digestibility and fecal characteristics, microbiota, and metabolites in dogs fed human-grade foods. J Anim Sci. 2021;99(2). doi:10.1093/jas/skab028

13.      Tanprasertsuk J, Perry LM, Tate DE, Honaker RW, Shmalberg J. Apparent total tract nutrient digestibility and metabolizable energy estimation in commercial fresh and extruded dry kibble dog foods. Transl Anim Sci. 2021;5(3). doi:10.1093/tas/txab071

14.      Buff PR, Carter RA, Bauer JE, Kersey JH. Natural pet food: A review of natural diets and their impact on canine and feline physiology. J Anim Sci. 2014;92(9):3781-3791. doi:10.2527/jas.2014-7789

Posted in Nutrition | 12 Comments