Health · Nutrition · Pet Food · Science · Uncategorized

The Raw Deal

I have avoided writing this essay.

The reason is that, contrary to how it may on occasion appear, I generally do not seek out conflict. Considered debate about scientific evidence and civilized discussions? Yep, enjoy those. However, the acrimony and polarization that frequently accompanies internet discussions about how best to feed dogs? Avoid those like the plague.

But, here’s the thing. I write about dogs and science. Over the last year or so, the number of published scientific studies that examine a particular aspect of raw feeding have continued to accumulate on my desk. I read them, sigh, and place them back on the pile.

My aversion to internet fighting was proving to be greater than my need to write science.

UNTIL NOW.

On my desk are three new studies, all in refereed, academic journals, and all reporting about the presence of pathogenic bacterial and parasitic contamination in commercially-produced raw dog foods.

IT’S TIME TO WRITE ABOUT THEM.

Here is what they say:


Study 1: Dutch epidemiologists with the Division of Veterinary Public Health in Utrecht, Netherlands, tested 35 commercial raw, meat-based diets (hereafter, RMBDs) for the presence of bacterial and parasitic pathogens (1). The researchers purposely selected popular brands that were sold by retailers. All of the samples had been stored according to label recommendations prior to analysis. Results: Escherichia coli (E coli) was found in 30 products (86 %). Twenty-eight foods contained an antibiotic-resistant strain of this microbe and eight were contaminated with a strain that causes serious illness in humans. Listeria species were found in 43 % and Salmonella species were found in 20 % of the tested foods. Several products were contaminated with parasites, but this risk was substantially lower than that of bacterial contamination. Conclusions: Because several of the pathogens that were isolated were zoonotic (i.e. are pathogenic to humans) and because the transmission of antibiotic-resistant bacterial strains is an increasingly serious public health issue, the authors conclude that pet owners should be informed of the potential health risks (to humans and to pets) associated with feeding RMBDs.


Study 2: Although conducted in pet cats rather than dogs, this study is important because it examines the effects of feeding a raw diet on changes in fecal bacterial populations and the potential for exposure to antibiotic-resistant microbes (2). The study enrolled 17 pet cats that were fed dry, extruded cat food or a combination of dry food and canned food (the control group), and 19 cats that were fed a frozen or fresh raw diet. Fecal samples were collected weekly and were analyzed for the presence of antibiotic-resistant forms of species within the intestinal bacteria family of Enterobacteriaceae. In addition, 53 cat foods (18 raw products and 35 dry or canned products) were analyzed for the presence of the same bacteria. Results: In the control group (cats that were not fed a raw diet), 3 of 51 samples (5.9 %) were positive for the presence of antibiotic-resistant microbes. In the raw-fed group, 37 of 57 samples (65 %), collected from 17 of the 19 cats, were positive for antibiotic-resistant bacteria. When present, the concentration of these microbes was also found to be significantly higher in cats fed raw diets. Finally, 77.8 % of the raw foods and 0 % (none) of the cooked foods were found to be contaminated with antibiotic-resistant bacteria. Conclusions: This study found a strong association between feeding cats a raw diet and fecal shedding of antibiotic-resistant bacteria. This association suggests a substantial risk of transmission of antibiotic-resistant bacteria to both the animals and to the owners who handle these foods and who may also be exposed to their pet’s fecal matter.


Study 3: In this study, samples of 60 commercially available, frozen RMBDs were tested for microbial contamination (3). Results: Bacteria of the taxonomic family Enterobacteriaceae were found in all 60 samples (100 %). In half of these (52 %), the concentration exceeded the threshold level considered acceptable by EU regulations. Clostrium perfringens was detected in 18 brands (30 %) and concentrations exceeded the maximum allowed in two brands. Salmonella species were found in 4 samples and Camplylobacter species were isolated in three samples. Conclusions: Like other authors, the researchers recommend that pet owners are informed about the pathogen risks associated with raw feeding. They also go a bit further, stating that in view of the antibiotic-resistance problem, dogs who are being treated with antimicrobials should not be fed raw diets; nor should dogs living in homes with infants, elderly people or immunocompromised individuals because these subgroups are more vulnerable to infection.


Review Study (March, 2019): This is the most recently published paper (4). The authors review more than 30 scientific studies, published in academic journals between 2005 and 2019, that measured bacterial pathogens in raw pet foods. In both Europe and the United States, a high proportion of the tested foods had contamination levels that exceeded the minimum acceptable levels for human meat products. The most commonly isolated pathogens were Salmonella and E coli. Most recently, antimicrobial-resistant forms of several different bacterial species have been reported. Conclusions: The authors conclude that there remains little doubt, based upon the published evidence, that the prevalence of potentially serious pathogens is substantially higher in raw pet food than in heat-treated foods and that these levels may pose a significant health risk to both pets and humans.


The (Raw) Deal: As it stands today, the research evidence regarding benefits and risks associated with feeding raw diets tells us this:

  • Health benefits? As with any broad category of feeding, the long-term health benefits of feeding raw foods to dogs is difficult to study. To date, most of the purported advantages of feeding raw are based on personal stories and anecdotes and do not have support from controlled feeding trials. The few feeding trials that have examined general health have reported that dogs fed a nutritionally balanced raw diet remain healthy, but have not demonstrated enhanced health benefits above those of dogs fed other foods. This does not mean that there are no benefits; it simply means that we do not know and that the numerous health claims for raw foods are not based on scientific evidence.
  • Improved digestibility and nutrient availability? Some owners select a raw food for their dog because they are interested in feeding less highly processed foods. In the dog food realm, both dry, extruded food (kibbles) and canned foods are highly processed and are almost exclusively produced from non-human grade (i.e. “inedible”) ingredients. The way in which these ingredients are handled and cooked during processing causes moderate to severe changes in protein quality and the loss of some nutrients. Therefore, it is not surprising to find that raw diets are usually higher in digestibility than processed foods. However, both digestibility and nutrient availability are dependent upon the quality of the starting ingredients, as demonstrated by a recent study of raw versus processed chicken. There is also evidence, from several researchers, that raw feeding alters intestinal microbe populations. What is not known however, is the impact, if any, of these changes upon digestive capacity or health.
  • Safety? The studies reported in this essay provide evidence that commercial raw dog foods are more likely to be contaminated with bacterial pathogens and with specific strains of these pathogens that are resistant to antibiotics. These results show that dogs and people may be at risk of infection and that these foods are a potential vector for the spread of antibiotic-resistant strains of bacteria to other animals and people. 

My intention with this essay was not to start an internet fight.  

However, the research says what it says. And currently, there are numerous studies, from different, unrelated laboratories, showing us that commercial raw diets are more apt to be contaminated with potentially harmful bacteria.

This is the science.

Deal with it: If you are a raw feeder, then deal with this information in the smart way. Ask producers about their methods for controlling bacterial contamination, about their quality control measures, and about their company’s recall history. Select foods that have been shown to be free of pathogenic bacteria and have not been recalled. When feeding, avoid handling raw products, wash your hands and food preparation surfaces thoroughly, and monitor your dog carefully for signs of illness or gastrointestinal infection.

The science tells you that these are the facts. It is your decision regarding how to deal with them. 

Cited Studies:

  1. van Bree FPJ, Bokken G, Mineur R, et al. Zoonotic bacteria and parasites found in raw meat-based diets for cats and dogs. Veterinary Record 2017; November: doi: 10.1136/vr.104535.
  2. Baede VO, Broens EM, Spaninks MR, et al. Raw pet food as a risk factor for shedding of extended-spectrum beta-lactamase-producing Enterobacteriaceiae in household cats. PLoS One 2017; November: doi.org/10.1371/journal.pone.0187239.
  3. Hellgren J, Hasto LS, Wikstrom C, Fernstrom LL, Hansson I. Occurrence of Salmonella, Campylobacter, Clostridium and Enterobacteriaceae in raw meat-based diets for dogs. Veterinary Record 2019; March: doi:10.1136/vr.105199.
  4. Davies Rh, Lawes JR, Wales AD. Raw diets for dogs and cats: A review, with particular reference to microbiological hazards. Journal of Small Animal Practice 2019; March:doi.10.1111/jsap.12300.

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Interested in learning more about how to critically evaluate and select the best food for your dog? Read Linda Case’s best selling book, “Dog Food Logic: Making Smart Decisions for Your Dog in an Age of Too Many Choices“.

61 thoughts on “The Raw Deal

  1. great article but it can or could be misleading. You speak specifically about processed raw foods that are prepared and not raw food from a meat counter. We have fed a diet of raw chicken for many many years without any kind of bacterial issues we are aware of all of it being human grade (which I still wont eat it ).

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  2. You are a brave soul and I couldn’t be prouder of you. And I have to say that I’m proud of the people who have asked respectful and thoughtful questions on your post (at least here on your blog…think I won’t visit your FB page on this one). 🙂
    For those of us who try to do the right things for our dogs, this type of information is so helpful. As you well know, transparency is not a quality that most commercial pet food companies possess. So we make our decisions based on the little information available to us. I’ve fed Raw for over 20 years, and now I know I can take a simple step of gently cooking and make it safer for my dogs (and my elderly mothers). And based on the information in your previous blog regarding the digestibility not being affected (and maybe even improved), WHY NOT?! Thanks so much for taking the time to do the difficult task of journal reviews to bring us this information.
    Planning to share with (and encourage) my clients as well, who buy commercial raw from my store.

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  3. I am a pet owner that recently switched my three dogs over to a kibble that is highly recommended by the owner of the pet store I go to. My dogs are doing just as well on the kibble if not better, as the levels of ingredients/nutrients/etc are all consistent where as kibble is it a bit of a guessing game to get the right mix done up for each dog. After reading this essay I am interested in reaching out to my raw food provider (as he is a small local business and sources all his meats himself) to see where he gets him meats and how the meat is handled, etc.
    Your essay is very thought provoking and all science based which I really appreciate. I am tired of looking for information on the difference of feeding kibble over raw and finding so many articles that attack raw feeding pet owners.

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  4. Thank you for compiling the research. What I would like to see is a side-by-side comparison of the bacterial contamination of human food e.g. raw chicken from the grocery store, with the raw meat pet food diets. I have a sneaky suspicion it’s not much different, and we handle raw chicken all the time assuming we are not vegetarians. If it IS different, the next question is why? Sloppy slaughtering practices, storage practices, what?

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  5. As always a good article. To add some balance all of the bacterium are naturally present in the gut of most if not all animals including humans. It would be interesting to know how much of the bacterium found in the studies was from the natrually occuring gut bacteria and how much was from contamination.
    Besides cooking to kill live bacteria does freezing kill them? A lot of UK Raw feeders will freeze meat, even that bought for human consumption but fed to pets, for 3 weeks to kill off any bacteria.

    Liked by 1 person

    1. Hi Olwen, Thanks for your note. Yes, of course bacterium are present in the intestine – and they are vital to normal GI and overall health. They are also expected to be present in all raw foods, which is why we typically cook meat before eating it. The studies do address when products bacterial levels exceeded acceptable levels for human foods (see my review, and the complete papers for more information). Freezing will kill most parasites and some bacteria, but only heat treatment kills Salmonella (see my answers below), so the practice of freezing raw foods for 3 weeks is not sufficient. Best, Linda

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  6. I currently feed a commercial raw food and my dogs seem to be doing well on it. I wouldn’t be opposed to feeding something else but they don’t like kibble. What’s a mother to do?

    Liked by 1 person

  7. First, applause for tackling the issue. I feed lightly cooked store so that I buy at a human grocer so I’m asking this question out of ignorance not because I’m a believer. But, if you tested human grade beef, chicken, duck, turkey, etc etc etc suppliers hat percentage would have bacterial or antibiotic resistant bacterial contamination? Isn’t it normal and isn’t that why proper cooking temperatures are so important?

    Liked by 1 person

    1. Hi Eve and Jacueline, Exactly! See my answer to “Milo” below. Your approach is the safest, by far and an approach that provides one of the highest quality protein sources. The point I would add is that if a person or a manufacturer is not using human grade ingredients, then those ingredients are almost certain to contain higher concentrations of microbes and parasites because of the way in which they are handled and processed in the by-product ingredient stream. Simply cooking gently to ~ 160 degrees F will not reduce nutrient value and will kill bacteria. Thanks for your thoughtful post! Linda

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  8. Interesting article. I feed my cats a raw diet. I can only go by what I have seen examples… a little street cat who fed 3 babues on the mean streets wAs so terribly thin. Despite giving her quality processed fish, her weight gain was slow. Within 2 weeks of feeding raw her weight gain was certainly noticeable by the eye. My Persian was on a dry food only diet by his previous family. His cost was full and dry. On moving to a raw diet it gained s shine and was silky soft. Cats produce so much poo on a highly processed foods. Why because it’s full if stuff their body doesn’t need or want.

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  9. I’m with you. Social media has driven us further apart than ever before. You can’t say anything without being ostracized or worse. Kudos to you for sharing this info, despite the potential for conflict. Just because someone disagrees with a premise should not diminish each person’s thoughts. Yet everyone seems to take things so personally from deep within their trenches rather than having a thoughtful, considerate discussion. *Sigh*

    Liked by 1 person

  10. Great, thanks. I cook because I have elderly parents in the house. As well, I’ve known for a long time that science shows that the bioavailability of nutrients in cooked foods is higher (slightly? Or a lot? not sure), so I figure I am taking care of my girl as well as I possibly can. She seems to love her “dog food soup” as well and is very fit, especially for ten years of age.

    Liked by 1 person

  11. Thanks for the good article. Pet Partners
    Has not allowed an animal to be a PP if they or ANY dog in the household is on a raw food diet. Glad to see the science behind it now.

    Liked by 1 person

  12. Hooray for science! I do feed raw (and wash everything very carefully) but given the high percentages of pathogens I really need to rethink this. This is one of those subjects that, as you said, we raw feeders secretly hoped not to need to address. Rats! and Thanks (:

    Liked by 1 person

    1. Hi Suzy – Thanks for your note. I mentioned this below in another comment. While freezing does not kill Salmonella and several other pathogens, gentle cooking does, so you may want to consider simply cooking your raw product a bit. Cooking (to 145 – 160 degrees F) is necessary. Remember – these data do not mean that all products are a risk, at all. In my view, they just provide information that warrants caution, or perhaps even cooking raw products gently, to 160 degrees or a bit above before feeding.

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  13. Thank you – a straightforward presentation of the available evidence, with a leavening of humour! I compromise, and cook for my animals, cats as well as dogs.

    Liked by 1 person

  14. Thank you for addressing this topic! I have looked into feeding raw several times, and the risks just seem to outweigh the benefits. Unfortunately with the rise of DCM in grain free and holistic foods, and the discouraging research on raw, those of us who are interested in feeding a less processed and more organic diet are running out of good options. Thank you for sharing!

    Liked by 1 person

  15. Thank you for this post. I don’t feed commercially prepared raw food for a bunch of reasons. First, it is ground up, which means that there is lots of surface area that can be contaminated. The second is that since it is all ground up, I can’t actually see what is in it, and the third is that I don’t really know the source of the various ingredients.

    I sometimes feed my dog a raw diet that I prepare and sometimes feed him a kibble diet. I would love to know about the risks of the home prepared diet. He gets chunks of muscle meat from a range of species and often gets chicken and turkey parts with bones in them, and various other goodies. The point is that they are all big pieces, that I can wash and freeze. This feels like it ought to be safer than commercially prepared raw diets. But this is difficult to test. I admit that I’m looking for loopholes in the studies because I can observe dental and digestive benefits in my dog. I am very careful about food safety.

    But, still, I am thinking about a switch to an all kibble diet, because of inferences one can make from the results of these studies to the risk of a homemade raw diet.

    It is a bummer when the science says things I don’t want to hear!

    Liked by 1 person

    1. Hi “Milo” – Thanks for your thoughtful post. (Love your blog, by the way!). I agree that we need more research regarding homemade diets, especially in this day and age when the issue of being balanced is really no longer an issue because there are several great ways to make sure we feed a well-balanced diet. If the meat that you are feeding is human-grade (i.e. was purchased from a butcher or supermarket), it will almost certainly contain lower levels of microbes. This is true for two reasons. The first is that the “ingredient stream” that these foods go into will be refrigerated from the very start and continues to be through point of purchase. This is NOT true of ingredients that come from the slaughter industry and are designated “inedible” (aka pet grade or by-products). Second, human meats will be subjected to regulatory oversight that governs human foods, but does not affect the by-products. It is the latter that are used by most, but not all, raw food producers. Last, if you simply cooked your raw food to 160 degrees F, you would kill Salmonella and other potential pathogens without harming the nutritional value of the foods. It is the poor quality ingredients, the lack of refrigeration and the extreme heat treatment to produce both animal protein meals during rendering and then the extruded kibble, that can reduce nutritional value (and possibly produce components that are not healthful). Thanks for your note and give a pat to Milo for me! Linda

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  16. Thank you for this!!!!! I’m a dog trainer and owner/handler near Chicago, and for years now I’ve actually felt vaguely embarrassed/defensive about feeding my dog Purina kibble! I just got sick of all the reports of bacteria or other issues with raw or boutique-y food options. I’m grateful to you for reviewing and “digesting” 😉 the science for us!!

    Betsy Lane

    Sent from my phone, possibly using dictation; please forgive typos and autocorrect’s errors.

    >

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    1. Hi Mollie – Yes, it disturbs me that several posters (on FB) have seemed to classify me in that way in response to this essay. In addition, several people in the pet food industry, who know me well and know that I am certainly not an apologist for the pet food industry and its practices, have heralded this essay as a “Linda Case comes out against raw foods” piece. It is not that at all. All that this essay provides is the current state of evidence regarding the degree of microbial and parasitic contamination to raw foods, and a brief overview of the state of evidence for health claims. That is all. (There are plenty of issues to worry about with highly processed foods, contamination issues, and ingredient quality issues with processed foods……that I write about in other essays). It is bizarre to me how emotional this particular issue has become. Anyway, thanks for your note! Linda

      Liked by 1 person

  17. Thank you. I doubt there’s ever been a time when lay-people have held their own opinions so high. These days, it’s become harder and harder for anyone to take in scientific information that doesn’t conform to their own expectations.

    Liked by 3 people

  18. I admire your bravery, I try to avoid talking about dog food on my own blog about dog marketing for similar reasons. Petfood may be highly regulated, but what manufacturers and retailers say and show about it is not!

    Liked by 1 person

    1. Thanks Cleo – I am definitely taking a few hits for this one, especially on FB (where I do not reply; the rude behavior of people just warrants no reply, imho). On the blog though (so far), folks have been interested and polite, so fingers crossed. I completely agree with you about what manufacturers are allowed to say – I have a webinar entitled “Super Foods and Super Claims” that addresses this exact issue (will be offering it as a Science Dog webinar later this year). Thanks for posting! Linda

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  19. Does the research include FREEZE-DRIED raw food? There are so many attractive options in this category I’m hoping that it’s safer…

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    1. Without more information, aren’t we trying to draw conclusions without knowing about the quality of the ingredients and the processor? Seems like we wouldn’t try to draw generalized decisions about kibble by lumping together Ol’ Roy and Solid Gold. And what about some of the more horrible things we are learning about some kibble recalls? I love your science, Linda, but I have more questions…

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      1. Hi Janet – I would definitely agree that the quality of the ingredients and processing methods are important considerations and have written about these issues in several blogs (see “Tastes Like Chicken” and “What’s the Deal with Meals” for more information). However, the topic of this blog is simply to examine the data that are available regarding bacterial and parasitic contamination in uncooked foods and whether the presence of these microbes may pose a health risk. Contamination can happen with any type of food, with high quality or low quality ingredients, so it is a bit of an apple/oranges type of issue. Thanks for writing in! Linda

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    2. Hi Idkeast – Most of the products were frozen, but the review paper may have included several freeze-dried products. The important point is that freezing (including freeze drying) can kill parasites and some bacteria, but it does not kill Salmonella and several other pathogens. For those, cooking (to 145 – 160 degrees F) is necessary. Remember – these data do not mean that all products are a risk, at all. In my view, they just provide information that warrants caution, or perhaps even cooking raw products gently, to 160 degrees or a bit above before feeding. Hope this helps – Linda

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  20. Thank you, thank you, thank you. I have long had my suspicions but didn’t have access to the data. I appreciate your reservations about putting this out there, and applaud you for doing so.

    Sent from my iPad

    >

    Liked by 3 people

  21. I am so happy you have addressed this topic. I have a few of your books, and subscribe to your blog because you present interesting information, know your subject and research the crap out of it. Your findings are always informative, and well written. You have a talent for presenting the information in an unbiased, sensible, readable way, and as a bonus have a wicked sense of humor. Thanks for the work you put into your research and for sharing it even though it may not be what a lot of dog people want to hear.

    Liked by 1 person

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