More Nonsense from Holistic Vets about Commercial Therapeutic Diets

One of the subjects that holistic vets and other advocates of alternative practices get really passionate about is the evils of commercial and conventional diets. They promote a laundry list of myths about pet food, many of which I’ve addressed before:

  1. Raw is better than cooked-

Raw Diets for Pets

2.Vets know nothing about nutrition-

This is particularly hypocritical given that the claims made about the evils of commercial food and the virtues of alternative diets are generally made by—yup vets!— and these folks have no more training or expertise than the rest of us. In fact, the most reliable source of expertise on pet food are board-certified veterinary nutritionists, veterinarians with extensive training in nutrition. However, their claims are casually dismissed with innuendos or accusations about financial bias by vets who themselves make their living selling the stuff they advocate for.

What do Vets Know about Nutrition?

3. You can tell the quality of a food from reading the ingredients on the label-

Sorry, you can’t. Partly this is the fault of regulators, who don’t require truly important information to be put on pet food labels in a clear and understandable way. And partly the uselessness of labels as a measure of food quality comes from the meaningless vagueness of the concept of “quality” and all the myths and misconceptions about specific ingredients promoted by these vets.

Pet Food Nutrition Myths
Nutrition Resources for Pet Owners
Dog Food Logic

A recent article from the ever-unreliable Dogs Naturally Magazine gave some alternative vets a platform for repeating some myths and misconceptions about what are often called “prescription diets,” though this is technically incorrect. These are better referred to as “therapeutic diets” because they are intended to be useful in treating or preventing specific medical problems, not simply provide good overall nutrition, but they do not actually require a prescription, merely oversight from a qualified veterinarian.

The evidence for these diets varies from strong (e.g. kidney diets for cats with kidney disease) to weak (e.g. some of the diets for cognitive dysfunction in older dogs), but while there are some good arguments against some of these foods, none of the ones made in this article are worth taking seriously.

The article begins by asking a bunch of holistic vets to rank a few foods based only on the ingredient lists, with one food being a prescription diet. Not surprisingly, the vets tended to rank this diet quite low, based on these sorts of arguments:

Dr Marty Goldstein, author of The Nature of Animal Healing [said] Food #3 ranked last, based on the use of corn for its first ingredient, followed by by-product meal.

Dr Jodie Gruenstern: “This food was the lowest quality in the list. It contains GMO corn, soy (lots of it!), which is a common allergen, synthetic vitamins/minerals, shavings (if you didn’t know, the ingredient cellulose is literally sawdust), natural flavors, which usually mean MSG.”

Dr Jean Dodds: “Poor quality food: the first ingredients are corn, which is often GMO, and chicken by-product meal rather than whole chicken. Flax and soy are phytoestrogens.”

Dr Judy Morgan: “This is a Pet Store Food. Corn is the first ingredient, no muscle meat used, only by-product meal, synthetic vitamin/mineral supplement, corn and soybean are GMO, waste fillers are abundant. Overpriced in my opinion, considering the poor quality, cheap ingredients used).”

Dr Dee Blanco: “This one starts with corn to increase inflammation, then adds lighter fluid to it with soybean products and poor quality protein. Then it tries to make up for the poor quality foundational ingredients by adding synthetic supplements of the poorest quality, such as calcium carbonate, folic acid, ‘generic Vit E supplement’, etc. Looks like they added l-tryptophan to calm the nervous system down after putting the body into overdrive inflammation. Natural flavors?? Could be an entire cadre of carcinogens, allergens and toxins. Argh!”

So we have a long list of villainous ingredients supposed to cause inflammation and other health problems. Any truth in this fear mongering?

Corn and Soy are Evil

Obviously, this sort of simplistic characterization of foods as inherently good or evil is not scientific in tone, and in the case of the particular claims she makes about these ingredients they are not consistent with mainstream opinion or the evidence. Veterinary nutritionists agree that particular sources of protein and carbohydrate in canine diets are not intrinsically harmful or beneficial and that the health effects of diet are a complex set of interactions between many factors. Duck and bison are no more nor less likely to trigger food intolerance than chicken or beef, and tapioca or potatoes or green peas are no better nor no worse than corn and wheat and soy as carbohydrate and protein sources.

GMOs are Evil

This is a hot-button issue these days, and while it is complex, the evidence to date does not support the sort of hysteria about GMOs these vets promote. This is, of course, a topic which deserves multiple posts on its own. Dr. Dodds and others regularly list GMO ingredients as unhealthy, promoting inflammation and food intolerance, and there is no evidence to support this. While there is always the potential that particular modifications of food crops and animals could lead to health risks, the anxiety about genetically modified organisms is generally ideological and based on misconceptions or poor understanding of the relevant science. It is part and parcel of the Appeal to Nature Fallacy, and the existing evidence does not support most of the hysterical fears about GMO. Dr. Dodd’s claims are not based on research from nutrigenomics but are simply part of her own beliefs and prejudices, and she provides no compelling scientific evidence to support her claims. Relevant discussion of this issue and the evidence can be found here: 1, 2, 3, 4, 5, 6, 7.

By-Products are Evil

Here’s what one nutritionist I’ve talked to has say about by-products:

A by-product only means that it was not the intended main product of the industry. It gives no indication on nutrient profile, digestibility and bioavailability, etc. Many people who dislike by-products will happily buy wheat bran (a by-product of the baking industry). Moreover, by-products vary according to country and culture. Liver, an excellent source of nutrition, is considered a by-product in the US because skeletal meat is the primary product of slaughtering an animal and many people do not eat organs any more. By-products can be excellent ingredients in pet food and it would be wasteful (and terribly self-centered) to not use it to nourish humans or animals.

The concept is meaningless, and used to demonize foods that people think of as “icky” without any reference to their real nutritional value.

Let’s look at some of the other claims. he idea that corn is a major cause of inflammatory diseases is an unproven hypothesis. The claim that phytoestrogens in soy used in pet foods have negative effects on health is an unproven theory. Both of these are presented as facts when they are just personal beliefs.

“Natural flavors” usually means hydrolyzed animal tissues, not MSG, so this is just false. And “synthetic” vitamins are identical to those extracted from plants, so the idea that they are somehow less useful or more harmful is just the Naturalistic Fallacy in action.

The bit about “sawdust is particularly silly. Cellulose is a natural part of the wall of plant cells. Sure, it is present in wood, but it is also present in all the fruits and vegetables that these vets would laud as healthy for our pets. The usual source of cellulose as a dietary fiber in pet foods is the bran from cereals such as wheat, not “sawdust.” Such hyperbole is clear evidence of a preference for ideology over facts.

The article also uses a bit of drama to suggest that therapeutic diets are poor-quality or identical to over-the-counter diets and the designation only serves to justify charging more.

Now, a 30lb bag of the regular food is $47.99 at Petsmart. The prescription diet dog food can also be purchased at Petsmart for $84.95 for a 27.5lb bag. It’s twice as expensive!

Now, you might be thinking this is because the prescription diet was formulated and tested with a specific condition in mind. This is completely false.

While an over-the-counter food with a health claim (such as controls weight) is subject to FDA regulations and enforcement, the FDA practices “enforcement discretion” when it comes to veterinary diets. Put another way, this means the FDA has not reviewed or verified the health claims on any veterinary diet. Did you catch that? There are very few ingredients in veterinary diets that aren’t also in other regular diets.

In the example above, I’d say the pet store brand is a better quality food, wouldn’t you? The prescription diet contains by-product meal (which comes straight from the rendering plant), lots of soybean and corn products (a cheap replacement for animal protein) while the regular food contains more expensive, higher quality ingredients.

Again, here’s the response of a nutritionist who actually knows something about veterinary diets to this claim:

This is a misrepresentation. Veterinary diet claims do have to be substantiated as well. The FDA did have some leniency regarding veterinary diets regarding the extent of their health claims because they are usually used under the guidance of a veterinarian to improve the life of the pets. However, the FDA is concerned about many so called therapeutic diets now marketed directly to the consumer, so they might start enforcing legislation if they are not used properly, i.e. under veterinary involvement

Regarding price, good companies invest in research, that goes into designing the food, sometimes funding basic research that would further our knowledge on particular diseases (without an immediate product to market and sell) plus trials in healthy and diseased pets, etc. So, I understand why a veterinary diet from a responsible company costs more money, not because the ingredients are more expensive, but due to the knowledge invested behind it.

These holistic vets are so ideologically biased against commercial diets that they even claim that ingredients they routinely recommend as beneficial for many health conditions magically become harmful when included in such foods:

And fish oil is a terrible addition to pet foods. It’s much too fragile to be added to processed foods and as soon as the bag is opened, it will oxidate and cause inflammation in your dog. Ironic isn’t it, when the food is supposed to be treating inflammation in the first place?

Actually, it’s not ironic, it’s just a bit of ignorance and prejudice masquerading as an informed opinion. Fish oils can be added to foods in a manner that has all the same health benefits of giving them separately, if this is done properly by a company with real nutrition experts who know what they are doing.

Bottom Line
I usually write brief summary of my conclusions for these posts, but in this case I could not write anything that makes the point better than the following, again from a nutritionist knowledgeable about these issues:

All these arguments are just guilt trips and not based on reliable science and assume the quality of a final product depends solely on certain random criteria form the individual ingredients rather than in deep knowledge of the current state of nutritional science, excellent quality control during formulation, reception of ingredients, extrusion, and storage conditions.

What we have here is unsubstantiated belief presented as fact. And this kind of fear mongering has real dangers. There is, for example, very good evidence that feeding commercial diets for cats with kidney disease can reduce suffering and prolong life. Yet I have seen clients feeding unbalanced and completely inappropriate homemade concoctions instead because they have been frightened and misled by this kind of propaganda and are unwilling to feed diets with proven benefits.

As I’ve said many times, no one knows the perfect diet for any given patient, and I am open to the possibility that there are benefits to feeding alternatives to the usual canned and dry commercial diets. But these benefits must be proven, not simply invented out of whole cloth or wrung out of twisted misrepresentations of nutrition science.

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41 Responses to More Nonsense from Holistic Vets about Commercial Therapeutic Diets

  1. Don Mac Kenzie says:

    The sad thing is that the reputable manufacturers are bowing to the woo, and are making “holistic”, “all natural” and “organic” labels available.

  2. Sarah says:

    My opposition to by-products has been because of the chance that different batches could have very different amounts of things – one heavy in organs, one heavy in bone, etc. Is that a reasonable assumption or am I misguided?

  3. Jennifer Hamlin says:

    I simply love your posts and I too am a skeptical scientist. Nutrition is certainly an emotive subject, for humans and for pets. I agree with you on many points, but there is one thing that I wish you’d address in your posts – with One Health being such a big factor moving forward with human and animal health, as a medico-scientific community we have some opportunities to broaden our understanding. I truly think we need to look at both ‘human’ evidence as well as the animal evidence.

    We have been using animal models for human studies for decades and one thing that we’ve learned about human health (often through animal models) is that ‘processed foods’ are not ideal for optimal health. We can feed our children without speaking with a nutritionist simply because the public education is so good that we can safely ensure our kids are reasonably well fed. Why can’t we do this for our pets? I’m not contesting what you’ve said, but as a skeptic, this is one area that really think isn’t being acknowledged in all the arguments for or against alternative feeding for dogs and cats. I’d love to see you look at the evidence around this.

  4. skeptvet says:

    While that is possible, every batch is balanced individually for key nutrients, so even if the exact ingredients differ the nutritional profile remains the same.

  5. skeptvet says:

    Thanks for the comment. As I’ve said before, there may be some advantages to fresh foods or home-cooked diets in pets. Unfortunately, there is no research on the subject, just a lot of opinion. I would love to see a good-quality cohort study, but it is unlikely since it would take years and be pretty expensive. And short-term, focused lab animal studies have some real limitations in terms of predicting the long-term health effects of different feeding strategies.

    I also wonder if, in practice, most owners would feed such a diet even if it were properly formulated and proven to be healthier. I refer people to nutritionists almost daily for guidance on home-cooked diets, and very few people are willing to put the effort in to do this right. It’s much easier, for those afraid of commercial foods, to feed table scraps or a haphazard collection of meat and vegetables that looks “healthy” but is nutritionally incomplete, and this is what I see many people choose. So that aspect of the problem has to be considered as well.

    I will also point out is that there is a problem with the term “processed foods” as used here. In the human food system, processed foods are designed and marketed for convenience and taste appeal, with nutritional value given little consideration. However, commercial pet foods are specifically designed and formulated with nutritional adequacy in mind, as well as palatability. The nutrient profile, digestibility, bioavailability, and so on are all specifically assessed and part of the process of creating the diets, and there are established nutritional standards with at least moderate evidentiary support that food must meet. So such diets are quite a different thing from the convenience foods that humans eat.

    Now that doesn’t mean there might not still be health advantages to whole food diets. Personally, I suspect there are. However, at the moment the alternative to commercial diets are haphazardly composed homemade diets that consistently fail to meet basic nutritional adequacy standards when the recipes are evaluated. I doubt that is healthier than commercial diets. So even the potential advantages of whole, fresh foods are irrelevant if most people who avoid commercial diets just end up feeding some meat and rice or maybe table scraps with no calcium source, no essential fatty acid source, and no appropriate micronutrient supplements.

    Finally, I’m honestly not sure you’re right that we feed our kids, or ourselves, adequately when we self-select foods. We know what a healthy diet is, but how effective are we really in implementing that given free choice? Obesity is a widespread and growing problem, and all the parents I know struggle mightily, often without success, to get our kids to eat what is generally understood to be an optimal diet. How many of us, adults or kids, actually eat a balanced variety of primarily fresh fruits and vegetables with reasonable quantities of whole grains and low fat protein sources? Given free choice, most of us fail to eat the kind of diet the evidence suggests we should. We are selected by evolution for an environment of scarcity, and we naturally seek excess fat, salt, sugar and so on because doing so was necessary to survival in that environment. Resisting those tendencies and selecting a healthy diet for ourselves seems to be something we fail at consistently. So I wonder, again, if a self-selected diet, for ourselves or our pets, really would be healthier in practice than a well-formulated commercial diet, even if it is better in theory.

    Good questions, and I’m sorry I don’t have clearer answers. I think the harms of commercial diets are mostly speculative, as are the benefits of homemade diets, and unfortunately the research is lacking to provide pragmatically useful answers to most of them.

  6. kathy kantel says:

    Isn’t the proof in the pudding? We feed our dog a commercial food recommended by his breeder that is manufactured locally but definitely has some of those terrible ingredients so decried by the holistic etc. lot. We also spoil him regularly with small amounts of table scraps. Our 5 year old is in beautiful condition, perfect weight, clean teeth so why would we change his routine?

  7. Re – Dogs Naturally Magazine. I took up their offer of the free vaccination guide for dogs and ever since have been bombarded with emails on pretty much a daily basis. The first ones were polite, offering discounts on subsriptions etc. They have now become more aggressive with a more negative conatations based on the premis that I am harming my dog by ignoring the information they have to offer. I am now being offered a free hearworm treatment guide!

  8. Jennifer Hamlin says:

    Another aspect that really needs to be looked with robust and unbiased research is the incidence of chronic diseases in companion animals. I’ve seen some discussion about the increased incidence of chronic diseases since the advent of commercial diets but I guess we won’t see evidence of a correlation between nutrition and disease in companion animals unless we have some reliable statistics pre-commercial diets to compare with.

    Even with human diets and the huge cohort studies on human nutrition and chronic disease, we still have such biased opinions around nutrition that seem to lead the charge rather than the evidence. Some questions I have: chronic diseases are on the increase with humans and there is a massive amount of evidence that plant-based diets can prevent/reverse disease – yet that majority of us refuse to accept it. How will we ever get to the point where we can do animal studies on such a large scale to find out if similar correlation between diet and disease exists? Anecdotally, we can see that the same chronic diseases in humans are being seen in companion animals and we know that nutrition is correlated with chronic disease in humans so is it to blame in animals as well? As we arguably won’t be able to get animal studies of the same human cohort size in animals, are we being unethical by refusing to extrapolate some conclusions from human studies? Dogs have been evolving along side humans for 10,000+ years. Yes, they may not have had the best health at all times, but they have not just survived, they have thrived. How did they get to this point when commercial foods are such a recent invention in their evolution? I am not convinced that we are being ethical. Evidence is great, and I am wholeheartedly a skeptical scientist, but there’s a point at which we need to think beyond our ‘education’ and resist the urge to follow a philosophy because ‘that’s the way it has always been done’.

  9. art malernee dvm says:

    So I wonder, again, if a self-selected diet, for ourselves or our pets, really would be healthier in practice than a well-formulated commercial diet, even if it is better in theory.>>>

    single source maintance diets are a risk factor for disease. They would need to make the “purina people chow” change from bag to bag to prevent things like the heart disease we created feeding only hills cd to cats. If you change the formula from bag to bag that makes it difficult to test the diet with a fresh ingredients grown locally placebo.

  10. L says:

    I like to use a quality kibble as a base (1/3-1/2 of diet) add bit of cooked lean meat, chicken, scrambled egg, tuna or something. Measured amounts twice a day, water added.
    I find my dogs are doing well on this regimen. I do notice a difference between cheap kibble and some of the higher priced ones though. Sometimes, dogs tolerate one product better than another.
    Back in the day we would just put down a bowl of dry kibble and leave for the day, assume they were drinking adequate water…..that didn’t work out very well.

  11. L says:

    I forgot to mention, I have used veterinarian prescribed dog food for different dogs over the years, with good results. I usually add something to it (once the dog is stable) to make it less boring.

  12. skeptvet says:

    It is worth bearing in mind, though, that chronic disease occurs because one lives long enough to get it. We actually live longer, healthier lives than any humans in history. The “rise” in chronic disease reflects a relative increase in these diseases as a proportion of the total morbidity and mortality, not an absolute increase in illness. What that means is that we are NOT getting sicker. We are simply suffering from different problems since we have eliminated those that caused the majority of our suffering for most of human history. Chronic kidney failure, heart disease, and cancer in the middle-aged and elderly were less of a problem when the majority of children died before 6 years of age and the average life expectancy was less than , which describes all of human history except about the last 150 years.

    So we have to remember that while we can absolutely discover and implement practices, including nutrition and exercise, to make us even healthier, it is simply not true that there was some golden age when we used to be healthier and now we have more disease because of our modern lifestyle. That is a misconception born of a lack of knowledge about the history of human health.

    As for our pets, it’s true that we don’t have good data on morbidity and mortality patterns across time. Some insurance studies and records from corporate practices like Banfield give us some sense of which diseases are most common, but there are a lot of limitations to these rather haphazardly collected data. I think it is quite a questionable notion that dogs and cats eating commercial diets are less healthy than those who used to eat table scraps, as was most common before the 1950s, but the data isn’t there to tell us. The closest dogs today come to their historical conditions living with humans are dogs in the third world who share space with humans but are not directly cared. They may be tossed leftovers or scavange trash, and they rarely get parasite prevention or vaccination. These dogs suffer constantly from preventable infectious diseases and parasitism (which they often share with local humans) as well as trauma and malnutrition. They don’t exactly “thrive,” and they generally have shorter and more uncomfortable lives than the housepets who eat these supposedly awful commercial diets and also get regular healthcare. So I think, again, we have to be careful about idealizing the mythical past and recognize that while things can always be better, they have likely been worse for most of history, for us and for our animal companions.

  13. Jennifer Robinsona comm says:

    Anecdotal, I admit, but I’ve known several dogs that lived long, healthy lives on cheap supermarket brands plus table scraps.

    Going beyond the anecdotal to a definitive study would probably cost billions. Requirements: Huge sample needed to account for diversity of dogs; many treatments needed to account for the differences in types of ‘raw’ diets, feeding quantities, and commercial diets. 10 years or more of study to seriously account for chronic illnesses. Lots of monitoring needed to account for the wide variety of ailments (allergies, cancer, skeletal problems, jecur, etc.). Not gonna happen.

    Personally, I think diet becomes a big issue because we tend to feel a lack of control in our lives. Diet is one thing that’s relatively easy to control. In my reading, there is some strong evidence that over-feeding is unhealthy (or under-feeding is healthy), and some extreme diets can cause problems . . . but for most dogs, a regular commercial diet does just fine, and all the razzamataz on the dogfood bag and in the holistic food industry is just marketing ploy with no scientific validation.

  14. Kelly says:

    By citing a “nutritionist” without providing a name and credentials that could be assessed, your “nutritionist’s” information/assessment is meaningless to me. You cite – by name – those who criticize commercial foods, but hide behind anonymity someone who refutes the criticism with presumed credibility (i.e. ” a nutritionist knowledgeable about these issues”). You gotta do better than that for your argument to have any credibility itself!

  15. skeptvet says:

    That’s total nonsense. In the first place, identity has no bearing on the truth of one’s argument, facts and logic do. Even credentials are of only very limited value, other than as a proxy for familiarity with relevant facts. In this case, you have factually inaccurate claims made by vets whose credentials are no different from mine. The fact that they made their names public has nothing to do with whether they are right or wrong. And while my acquaintance’s credentials do suggest greater knowledge on this subject than these holistic vets, ultimately they don’t matter. I simply referenced her comments because she did a great job of expressing the facts and arguments I wanted to highlight, and it would have been dishonest to present her words as mine. The facts are still the facts regardless not only of her credentials but of her identity.

    And finally, you are being a hypocrite if you are suggesting that the identity of this person has any effect on your willingness to accept my claims and arguments as true. If I told you her name, it would change nothing in your beliefs or your evaluation of my article. You are simply using the issue of identity as an excuse for rejecting a criticism you dislike. If I replaced her comments with those made publically by another nutritionist, you would simply shift the grounds of your rejection to something else, likely some BS about how nutritionists don’t have any credibility anyway because they are dupes or shills for the food industry, which is the sort of argument advocates of alternative nutritional practices often make.

    So if there is some specific point I have made you think is in error, you are welcome to provide actual evidence to contradict it. However, if you just want to find a shallow excuse for ignoring the facts, then you aren’t saying anything useful or persuasive.

  16. Kelly says:

    Wow! I really hit a nerve here with you. You have attacked me on so many levels, and accuse me of ” . . finding a shallow excuse for ignoring the facts. . . ” . Hmmmm – I didn’t realize you were telepathic. Oh wait – no of course you are not – because that is NOT at all what I am/was thinking.

    you wrote: “. . . identity has no bearing on the truth of one’s argument . . ” Seriously!! you think not providing the name of your “source” should have no bearing on your/their argument or comments. Then you are misguided. If you told me that you had a ‘source’ who insists that Round-up is not harmful to the environment – with “facts” to back it up – you don’t think it would matter to your readers that your “source” works for Monsanto?? or a scientist who claims that they “know” that global warming is not happening or is not human-caused – but who happens to work for Exxon – has no bearing on their opinion/facts/ or whatever they are trying to push?? How about all the claims from the tobacco industry who spouted for years that smoking was not harmful – when they sat on stacks and stacks of data to the contrary — you would offer their “argument” in your blog that smoking is not harmful?? Wow!

    I cannot do the studies. Therefore I must rely on the data, comments, facts, concerns of others who ‘claim’ to have some knowledge of the topic at hand. And I must also weigh their knowledge and experience of the subject matter to help me decide where the truth lies. Ultimately – I cannot “know” the truth unless I do the studies. If I do not have the empirical data, then I must rely on the knowledge of others, and I either “trust” a source or I don’t. But if I don’t know the background of a source – I will not blindly trust them. Sorry. But if you expect your readers to “trust” you . . well . . then – nevermind.

    And Please don’t assume you know what your reader’s intentions are in drawing conclusions (or not) from you blog (that I’m looking for some excuse to discard your source’s comments). That’s rather arrogant.

  17. skeptvet says:

    Your comments about dismissing any opinions from people you consider to have a financial conflict of interest simply reinforce that you are using the Guilt by Association fallacy to dismiss opinions you don’t like. I’ve already said the person I quoted is a board-certified veterinary nutritionist. Assuming this is true (and there is no reason for me to make that up), what difference would their name or place of employment make in terms of the comments I quoted? If they are a university researcher, would you suddenly agree with the comments? If they work for a pet food company, does that mean you can ignore what they say? You are simply assuming that any opinion can be judged solely on the basis of the associations of the person having it, and that is false and self-serving reasoning.

    It is true, you cannot learn every fact by direct experience. But if you are choosing to trust the sources in the article I critiqued and not me (whose credentials are easily verified) or the source of the comments I quoted, then you are making an ideologically motivated choice, not a discrimination based on any reasonable evidence that one source is more reliable than another. And, as I’ve already pointed out, the criticism I am making does not rest on the credibility of the person I quote anyway, since the comments I cited were simply chosen as illustrative. If I replace them with my own assertions of the exact same facts, does that suddenly make them more reliable because you know who I am? What excuse will you find then for rejecting them?

  18. Jennifer Robinsona comm says:

    So, what can we do to get better advice via diet? For example, the evidence regarding diet and hip dysplasia is confusing and inconclusive (insofar as I can digest it). The evidence on allergies is equally confusing. I want my dogs to be healthy. I don’t want to be taken for a fool by the product differentiation maneuvers and guilt mongering of dog food producers. Linda Case provides a lot of useful background, but as a retired scientist, I find her attempts to educate people on the scientific method tedious, and her conclusions inconclusive.

  19. skeptvet says:

    The problem is that definitive conclusions about “good” vs “bad” diets, or about the optimal diet for any individual pet, simply aren’t justified by the available evidence. Just because we want to be able to make firm, reliable conclusions about what to feed doesn’t mean we always can. Uncertainty is frustrating but sometimes it is a reality.

    I would say the best advice will come from board-certified nutrition specialists, but this level of input is probably only needed for animals with specific health issues related to nutrition. Otherwise, the basic principles would be something like:

    1. Don’t overfeed. Overweight body conditions is the most significant nutritional risk factor for disease known, and reasonable caloric restriction has been consistently shown to have health benefits.

    2. Feed a commercial diet that meets basic adequacy standards or a homemade cooked diet formulated by a nutritionist.

    3. Monitor body weight, lean body mass, stool and coat quality, and other measures of well-being and if they do not seem to be optimal, feel free to do some trial and error changing of brands or diets, accepting that the results are of limited value for generalizing about the feeding of other pets.

    4. Don’t get rigid and dogmatic about specific ingredients, brands, etc. The label really tells us almost nothing of value about the health implications of a particular food.

    5. If it sounds revolutionary or too good to be true and isn’t supported by extensive, consistent clinical research, it’s probably just opinion and not very reliable advice.

  20. lorac says:

    “Dog Food Logic” by Linda Case is an excellent resource on this subject, IMO. She discusses the science and research studies, analyses the results, and presents a fair assessment. No vilification of either the commercial, dry diet or homemade, raw diet. Her stated purpose is for dog owners to make informed choices.

  21. Gr8 k9s says:

    How can the so called traditional diet of dogs compare to the human-grade, premium meats of the modern raw fed dog? Go back to the parasitized, 4D, rotten meat of time gone by for a real traditional diet. In the wild, the predator thins the herd by killing the outliers- the old, diseased or injured. Once killed, the meat can sit around, unrefrigerated, for days. Fermenting and growing …. things. The real “biologically appropriate” diet would also allow a test of the theory that raw fed dogs don’t get salmonella, intestinal parasites, etc.

  22. Camilo says:

    I remember when I too fell for the generic nutritionists’ response regarding by-products. They would give their talk at lunch and learns and say, “Byproducts are perfectly fine, but it’s the ‘ick’ factor that consumers are responding to. In certain cultures, tripe, heart, liver, and even kidney are consumed readily, and those are ‘byproducts.'”

    To a born Colombian, this argument made perfect sense as we have dishes that I loved that included tripe and beef heart. Yup – a genius argument that resonates well with people who don’t actually understand what they are talking about. I once, did not understand the commercial pet food industry.

    Now that I’m more knowledgeable about the industry – I realize how ridiculous this argument is. Quite frankly – it’s misleading and insulting.

    There is a HUGE difference in quality, and in turn, possible effect on your health and nutrition between beef liver, heart, or even tripe that has been inspected and approved by the USDA for human consumption (by a USDA officer at a meat processing facility), and the ingredients that the pet food industry call byproducts. The same rules and regulations that exist for handling, transport, and storage simply do not exist for rejected carcasses and the left overs of the human food chain. To compare the two and call any criticism of feed grade byproducts a result of the “ick” factor is to pull wool over everyone’s eyes. It’s irresponsible that any nutritionist made such a comparison, or they don’t know the difference, which borders on negligence, given their specialty.

    Hope that helps,
    Colombian Vet

  23. skeptvet says:

    Easy to say, but I notice that you don’t offer any evidence to support this opinion. This is typical for those who complain about negative health effects from byproducts. Where is the evidence that this actually occurs, of that the change in ingredients you seem to recommend has any benefits? Anything besides opinion and anecdotes?

  24. Dr V says:

    This is more of a general question inspired by your post. At what point is so-called anecdotal evidence promoted to the status of evidence-based medicine? I ask because like many who have commented here, I am interested in the long-term effects of feeding home-prepared diets that vary from batch to batch and do not lend themselves to scientific studies.

  25. skeptvet says:

    There is no such point. Anecdotes do not become more reliable the more of them you collect because each is equally likely to be wrong. Literally thousands of people over centuries believed, for example, that bloodletting was a safe and effective therapy for a wide range of medical problems. The consistent and enduring nature of these anecdotes did not make them any less mistaken because they all rested on the same false concepts and unreliable observations. The most anecdotes can ever do is suggest hypotheses which we then have to demonstrate as true or false with controlled research.

    I don’t see, however, that there is any reason why studies on the advantages of home-prepared diets can’t be done in principle. Even observational studies, where groups of animals are followed and associations between diet and health outcomes are evaluated, are more reliable than anecdotes, though they have limitations as well. We have less control over what humans eat than over what we feed our dogs, yet we have a lot of evidence concerning the health effects of various dietary patterns. It’s not easy or inexpensive, but it is absolutely possible to demonstrate the proposed benefits of such diets scientifically, and ultimately we can’t confidently claim they exist unless we do so.

  26. Camilo says:

    Serioulsy? Where is your evidence that feeding processed, extruded byproducts from an unregulated chain of custody that is essentially the rejected ‘scraps’ of the more highly regulated human food chain is healthier? Where is any of the evidence that these companies claim exist – oh wait – it turns out … it doesn’t exist: http://www.petfoodindustry.com/articles/5955-mars-petcare-settles-with-federal-trade-commission

    Mainstream adoption is not evidence. I admire your skepticism, but where is it when it comes to questioning the unproven methodology of feeding our companion animals, who are expected to live 10-15 years, with feed that meets the same standard (no standard) as livestock and food production animals that live only 5 years?

    If you’re right, and the lack of evidence is suggestive of it’s safety (both ways), then why don’t we feed the third world extruded food made from byproducts of our first world waste? World hunger solved because this stuff is so safe. Or, maybe it’s not. Maybe we’d be harming people if we did that? To your point – we should look into it objectively, but we can’t because independent funding in veterinary nutrition research is rare.

    I’m amazed that you are asking for evidence that an official federal inspection and approval process is healthier than just throwing all the scraps in a truck and sending it to a rendering plant. By that logic we should just do away with meat inspection and just make all processed foods – there’s no evidence it’s keeping us healthy. HA!

    I like what you are doing, but I think you’ve crossed the line into an ironically pious form of targeted skepticism. It’s like an extreme, fundamental skeptic that cannot innovate due to their own skepticism that there’s no scientific proof that innovation is beneficial.

    Where’s the conclusive proof (the research) that this blog has had any impact on, well, anything at all? Because, by your logic, if you don’t have a peer reviewed, published study showing that this blog is worth maintaining, then you’re wasting your own time, right? A few people saying they like your posts is just anecdotal, after all …..

  27. skeptvet says:

    First of all, your sarcasm doesn’t serve as evidence that your assertions about the supposedly terrible nutritional quality of ingredients in commercial diets are true. This has nothing to do with human nutrition and you allusions to that are just dramatic handwaving. Likewise, nothing I’ve said has anything to do with “innovation,” and the effects, if any, of my blig are irrelevant to YOUR claims about pet food ingredients. All just smoke and mirrors to make it sound like you’ve made a case for something when, as I keep pointing out, you haven’t actually provided any evidence, only your opinion.

    Secondly, the demand for evidence is properly made towards the person making a claim. You claim the ingredients in these diets are inferior and cause disease, so it is up to you to provide evidence than this is true. If I claimed that commercial diets were healthier than homemade diets, then it would be my responsibility to provide evidence of that, but that’s not what I’ve said. What I have said is that homemade diets often turn out to be nutritionally incomplete, and that there is no evidence to support they lead to better health outcomes. I also claim that there is evidence for health benefits of some specific commercial diets (for example, studies showing improved outcomes in cats with renal disease fed diets formulated for this purpose). These are claims I can support. Homemade diets may well be healthier than commercial diets, and I have acknowledged that is possible repeatedly. But possible is not the same thing as proven, and there is currently no real evidence to support this claim, so it is merely a hypothesis.

  28. Dr V says:

    I think the meta-problem here is that our clients care little about studies when it comes to choosing what to feed their animals. They want a sense of control, i.e. they do not want to feel helpless. A locally sourced raw food with very few ingredients is much better at inspiring that sense of being in control than a commercial food with a very long list of ingredients that come from goodness knows where (China, heaven forbid). Yet they will readily buy a commercial food whose long list of ingredients they can understand, especially if it has the word “organic” popping up frequently enough.

  29. skeptvet says:

    Yes, feeding is absolutely associated with the sense that one can ward off bad things happening to one’s pet if they just feed the “right” food. It’s an understandable impulse, but when it leads to bad dietary choices it actually can be harmful. We don’t want to sacrifice our pets’ wellbeing for our feeling a sense of safety and control.

  30. J H says:

    While I refer to your blog often and have found a great deal of very helpful info that has often changed my thinking I am now a bit skeptical of it after reading your harsh reply to Kelly.
    As I was reading the actual entry I too was immediately drawn to the fact that your nutritional source wasn’t named. I found that suspicious. Anyone with common sense knows that you shouldn’t blindly trust an anonymous source. I need to vet them myself before I go along with them. I wouldn’t believe anything you said if I couldn’t check your credentials myself. Even if I end up agreeing with what you say (which more often than not I have), it’s not enough for me to trust your sources without you citing them.
    I am now second guessing everything here. Your unnecessary attack on Kelly and the assumptions you made because she pointed to a red flag is quite disheartening. And was insulting to her and others who are willing to accept your education & experience as long as we can look deeper into the sources. That’s not too much to ask at all. In fact I would think you would not just believe a colleague who cited an anonymous source based solely on the fact that you trust them. That’s not the right way to do research.
    Personally I don’t look here to go against what you say. I want facts.
    And I want to know where & how you come to your conclusions.

  31. skeptvet says:

    I’m sorry, but I really don’t see that my response was unduly harsh or inaccurate. The bottom line is that people are always saying to me, “I don’t have to believe anything you say no matter what evidence you cite until you tell me who you are and what are your credentials.” The, when they see my credentials, they invariably find another reason to dismiss what I say anyway. Often the next excuse is that because of my credentials I’m biased and so cannot be trusted. I have never seen the argument about anonymity used in these comments in any way except as an excuse to reject something someone disagrees with without dealing with the evidence itself.

    The person I referenced is a board-certified veterinary nutritionist in academic practice. You can believe that or not as you choose. The question is whether or not that information makes a difference. It isn’t appropriate to reject or accept a claim on the basis of the background of the person making it anyway. That’s the Argument from Authority fallacy. Sure, experts are more likely to have access to relevant information, but their expertise in itself doesn’t make them automatically right or wrong. So I don’t see that it strengthens my argument if I publish my friend’s CV (and subject her to all the vitriolic hate mail I get daily for this blog), and I don’t see that it weakens it if I simply tell you what her credentials are. In either case, the merits of the claim are what matters, not the resume of the person making it. If your primary reason to believe or not believe me is my CV, then you really are missing the point of the blog, which is about relying on evidence not authority to judge claims.

  32. Brian Wessels says:

    Subject = Canine commercial diets, as well as homemade diets for dogs.
    According to the experts ancestral dog (canine) ‘arrived’ on earth about 180 million years ago. Once again, according to the experts, Man began domestication of dogs (canines) about 25 to 30 thousand years ago. This domestication took place without the aid of commercial food companies and veterinarians. It is only during the past 350 to 500 hundred years ago that Man began to ‘create’ the different breeds by very selective breeding. Once again most of this has taken place without the addition of veterinarians and commercial food companies. Consequently, present day dogs have survived these millions of years of generations by eating what Nature intended a
    carnivore to eat. Is this not proof enough?
    If ‘ancestral’ dog had to have suffered with the huge number of problems that present day dogs are diagnosed with, AND there were no veterinarians, then I summarize that we would not have present day dogs.
    For a diet to be “adequate” and “complete”, it must pass the test of great conformational growth, the diet must achieve the ability of all individuals to breed maximally, and then allow individuals to achieve a great, active old age. Nature achieved this without veterinarians and commercial food companies.
    In conclusion, and in my opinion, follow Nature – in the long run, Man will not beat Mother Nature. Breed small animals (rabbits, rats, mice) and give the canines what Nature intended the carnivore to eat.

  33. skeptvet says:

    Consequently, present day dogs have survived these millions of years of generations by eating what Nature intended a
    carnivore to eat. Is this not proof enough?

    There are two problems here. First is the idea that because the ancestors of modern dogs “survived,” that means that what they used to eat was somehow optimal or better for them than what they eat now. Our ancestors survived for millions of years without modern nutrition or medical care too, but they suffered more and died much earlier than we do. The fact that dogs used to eat something other than commercial pet food says nothing about whether what they used to eat is better, or as good as, modern diets.

    The phrase “eating what Nature intended.” is also a fallacious one. What animals in nature eat is what they can get, not what is the best possible diet for them. Animals in nature suffer from parasitism, malnutrition, and death from starvation all the time. So again, the fact that wild carnivores can sometimes survive on what they find in the wild, and that dogs have been able to survive eating different diets than they now eat, doesn’t say anything about what is the healthiest diet for them.

    ‘ancestral’ dog had to have suffered with the huge number of problems that present day dogs are diagnosed with, AND there were no veterinarians, then I summarize that we would not have present day dogs.

    Nonsense. Ancestral humans suffered from rickets, scurvy, plague, and all sorts of ills we don’t have to endure.The fact that they could still produce enough babies to keep the species going before modern medicine doesn’t mean they were happier or healthier than we are now that we have such medicine. Similarly, the fact that dogs didn’t die out as a species before modern diets and healthcare does not imply that such diets and healthcare are bad or unnecessary. That’s simply ridiculous.

    he diet must achieve the ability of all individuals to breed maximally, and then allow individuals to achieve a great, active old age. Nature achieved this without veterinarians and commercial food companies.

    No it didn’t. You have some fantasy in mind about the Nature as some Edenic paradise, when the reality is that in Nature there is constant suffering and widespread death, often from causes modern science has greatly diminished or eliminated. Even today, hundreds of thousands of dogs die of rabies every year in parts of the world where they cannot be vaccinated, and almost none die in the US where they can. Nature is not a benign goddess giving health and wellbeing to her children. It is just the state of living things struggling to survive as best they can with what they have, often with great suffering. Whole species are lost to death and disease and changing circumstances throughout the history of all those millenia before humans started to influence nature, and while we have not solved every problem, and we have created plenty of new ones, it is naive and ridiculous to imagine that we or our dogs were better off before science and medicine were developed. Pure fantasy, nothing else.

  34. No one says:

    “and tapioca or potatoes or green peas are no better nor no worse than corn and wheat and soy as carbohydrate and protein sources.”

    I’m not sure about tapioca or green peas, but from the research I’ve read (or at least part-read-part-skimmed.. I still don’t quite have the tenacity or knowledge to laser-analyze every piece of data in the papers I read :p ),
    soy doesn’t necessarily seem so great.. for whatever reason it seems to be considerably less digestible than a lot of the other plants they put in food. I’d definitely pick corn over soy

    Do you have any insight?

  35. skeptvet says:

    I would be interested in examples of the research you are referring to, since I don’t see a lot of evidence that soy is generally inferior to other nutrient sources, though I know this is sometimes claimed.

  36. no one says:

    “I would be interested in examples of the research you are referring to, since I don’t see a lot of evidence that soy is generally inferior to other nutrient sources, though I know this is sometimes claimed.”

    Oh.. oh my.. *hangs head* looking back over the two studies I was thinking of, it is that they use soybean meal, not just pure soy protein. So of course any fiber that gets included will reduce the digestibility..
    And what’s more is it was comparing it to meat protein sources, not other plants! Oh shame! (And it actually still fared better than some of them, like that wonderful meat-and-bone meal).

    I won’t bother linking them unless you’re really that interested, since my original point was pretty much nullified :p

    Sigh, I try to read so much research (I’m actually writing up little research papers/comics for my coworkers), and I go back over and over things, but these little crucial things end up slipping my mind later on. I guess it’s a good thing I never write anything as a certainty and try to remember the human tendency to make mistakes :b.. (I know when I wrote my paper I was more precise about all these data as well).
    I guess in this case, it’s also that I always see soybean meal as an ingredient, rather than just soy protein, so it became pseudo-synonymous for me, you could say

    Do you have any advice for my pursuit in cultivating the discipline of mind to get better at avoiding these mistakes? lol .. I often find myself scattered and disorganized in thought — I’ll find myself having to skim back over papers and research again and again after realizing some tiny flaw in something I thought was correct. Perhaps just go more slowly to begin with? It is overwhelming at times though, all this information (and that I have no sense of statistics or anything that would allow me to assess how data are analyzed, beyond some very very limited understanding of p-value). It feels like trying to hold onto 100 tennis balls in my arms that I can’t quite keep from falling to the ground 😐

    And yet even with these failures, I find myself better equipped than ever to discuss nutrition, with many of my old stupid assumptions replaced with a more complex understanding. (I have to talk to customers about these things on a daily basis where I work).

  37. skeptvet says:

    There are some great resources for learning to critically appraise research papers if you are interested. Here are just a couple:

    The Pocket Guide to Critical Appraissal

    How to Read a Scientific Paper (for non-scientists)

    Another guide for lay people on reading a scientific paper

  38. Ron says:

    skeptvet says:
    July 21, 2016 at 8:31 am
    “While that is possible, every batch is balanced individually for key nutrients, so even if the exact ingredients differ the nutritional profile remains the same.”

    How do you Know , For Sure?
    Every batch is also cooked at very high Temperatures and than extruded a few times, destroying any values the food may have add at the beginning. Of course they do spray on some vit/ min mix at the end to meet the nutritional profile.

  39. skeptvet says:

    The large companies have quality control processes for verifying the nutritional composition of different batches, which is part of why these diets are often more consistent than products from smaller companies. Now, if you believe these processes are ineffective or the results falsified or for some other reason you don’t trust them, that’s up to you, though unless you have some specific evidence for those concerns they are just conjecture.

    Cooking does alter the nutrient profile, reducing some nutrients (e.g. some vitamins) and enhancing others (making protein and complex carbohydrates more digestible, for example, which is why we cook our food). So it is not correct to say this “destroys any value the food may have had.” And, as you say, this is compensated for by adjusting the nutrient composition after extrusion, so it’s unclear that extrusion is a problem from a nutritional point of view.

  40. Ron says:

    My problem is not so called “prescription diets” , but that there is no legal standing for using such a term in pet foods or one that even Should require a script from a vet.

    From my research, the prescription diet is an industry coined word and does not have any legal meaning or any special regulations or guidelines.

    I would also wager that if you put six nutritional consultants in the same room, whom incidentally are employed by the manufactures. I’m not sure I could say their opinions are unbiased toward their own foods.
    Now if you could find someone totally objective and unaffiliated in anyway with the producers or industry, that could be another story.

  41. skeptvet says:

    The term “prescription diet” is actually copyrighted as a brand by Hill’s. The technical term for diets intended to treat or prevent disease is “therapeutic diet,” and this does refer to diets given a special status by the FDA, though not under the same guidelines as prescription medications and not under the same legal restrictions. There is a legitiate medical, not merely a financial, reason for requiring veterinary supervision for the use of these diets.

    As for objectivity, no one is “objective” about anything if by that you mean they have opinions which are purely unbiased and fact-based without any influence from pre-existing beliefs or personal experiences. However, I find people only mention “bias” when it undermines a perspective they disagree with, and they tend to deny it when it is associated with claims or opinions they hold. Proponents of raw diets are just as biased as nutritionists working in industry, whether by financial motives or other ideological biases. .That is why scientific evidence, however imperfect, is still the best guide for making medical decisions.

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