The Science of Raw Pet Food

One of the most common arguments that opponents of raw diets use to discourage owners from feeding raw is that there isn’t enough research to prove raw diets are safe or effective. While we can all agree there are not nearly enough clinical studies comparing raw diets and kibble, I disagree that there is no evidence to support the idea that raw diets can be more beneficial and safe for dogs, cats, ferrets, and other meat-eating pets in comparison to a commercial dry food diet.

Unfortunately, there is a high prevalence of logical fallacies and misinformation in many raw feeding resources and circles, which only helps to further diminish the legitimacy of raw diets. This article will aim to address the current science based evidence that can be used as support of the merits of raw food diets.

Commercial dry pet food has significant drawbacks

First we must address the reasons owners choose to feed their pets a raw diet instead of a commercial dry food. Despite it being more time consuming, less convenient, and typically more expensive, the number of owners choosing to feed raw continues to grow. Why is this?

A large majority of pet owners decide to stop feeding kibble because they don’t believe that pet food manufacturers have their pet’s best interest in mind. There is evidence to legitimize this distrust; countless commercial pet foods – even supposed “higher quality” formulas – have been found to contain undeclared ingredients [1, 2, 3, 4, 5, 6] and contain unacceptable levels of harmful bacteria [7], mycotoxins [8, 9, 10], euthanasia drugs [1112], and other contaminants [13], resulting in significant health concerns and even death.

Even if not contaminated, dry food can come with its fair share of drawbacks. Dietary moisture is very important for excretory health in dogs, cats, and ferrets. Dry food is naturally very low in dietary moisture, which can result in higher urinary oxalate and calcium excretion rates [14, 15] and higher instances of idiopathic lower urinary tract diseases in cats [16], dogs, and ferrets [17]. A large amount of dry pet foods on the market are high in carbohydrates, which has also been associated with a higher risk of urinary stones [18] and obesity [19] in cats and dogs.

The production of commercial pet food can involve high heat treatments including sterilization, extrusion, cooking, and baking. It is well documented that high heat processing and extruding can have a negative effect on the available nutrition of a food, as can extended periods of storage [20, 21, 22]. An extruded pet food diet will contain significantly less available amino acids such as lysine, glycine, taurine, arginine, cysteine, methionine, and creatine in comparison to a raw pet food diet [2324, 25].

One of the most common effects, the maillard reaction, is a chemical reaction that occurs between amino acids and reducing sugars when exposed to high heat, rendering those amino acids unavailable for metabolism. This reaction occurs during pet food processing, putting commercial diets at risk of not meeting minimum requirements for many of these amino acids [26, 27], and at risk of containing high levels of advanced maillard reaction end products (MRPs) and advanced glycation end products (AGEs) [28].

MRPs and AGEs have been linked to various health issues, including but not limited to food allergies, diabetes, Alzheimer’s disease, cardiovascular disease, and impaired renal function in humans [293031, 32] and other animals, including dogs and cats [33, 34]. Increased intake of these end products has been thought to negatively affect the microflora of the digestive tract [35] and the bioavailability of amino acids [36] and other nutrients, including magnesium [37], phosphorus [38], calcium [39], and iron [40], among others. Further, high levels of dietary AGEs have also been associated with liver inflammation [41, 4243].

“Complete and balanced” nutrient values have been determined by the NRC, AAFCO, and FEDIAF to use in the formulation of commercial pet food diets in order to meet the minimum physiological requirements of pets. However, significant concerns have been raised regarding the validity and accuracy of these values.

The minimum protein and amino acid requirement estimates of the NRC were determined using unprocessed, highly digestible ingredients. But when formulating commercial foods manufactured using high heat treatments, less digestible ingredients, and extended periods of storage, these bioavailability estimates could result in nutrient concentrations that do not ensure minimum physiological requirements are met. A closer look at the calculated bioavailability estimates by the NRC, AAFCO, and FEDIAF shows that they are “inadequately referenced, not citing scientific studies, and lack scientific veracity” [44]. These issues were brought up over a decade ago [45], but have yet to be adequately addressed.

For these reasons, it isn’t far fetched to speculate that commercial pet foods may be a contributing factor in many of the common “idiopathic” conditions our pets are experiencing. Considering that commercial pet foods are typically the sole source of nutrition for dogs, cats, and ferrets, we should not ignore the potential long-term health implications and the effects on amino acid and nutrient bioavailability in dry food diets.

Benefits of raw foods

It is well known and accepted in human nutrition that fresh, whole foods are generally more nutritious than processed foods, and that while eating processed foods isn’t necessarily a bad thing, it isn’t optimal to rely solely on processed foods for all of your nutritional value. There is no definitive proof that this would not also apply to our pets.

It is well known that raw animal products contain significantly higher levels of amino acids than commercial pet foods [46, 47, 48, 49]. It has been shown that obtaining more than the minimum recommended dietary amounts of many essential and “semi-essential” amino acids can be beneficial [5051, 52]. Whole, fresh, minimally processed foods also contain more enzymes, friendly bacteria, beneficial phytonutrients, antioxidants, fatty acids, and more that will not be found at nearly the same levels in highly processed foods [53, 54].

For this reason, research in nutrition science has been placing more and more emphasis on foods rather than individual nutrients [55], based on the premise that it is healthier to obtain nutrients directly from primarily whole food sources rather than from primarily synthetic or fortified sources.

In comparison with dry extruded pet foods, research has consistently shown that raw foods have a higher nutrient digestibility in dogs [56], cats [57], and ferrets [58]. Recent studies have also shown that raw diets can promote a healthier gut microbiome in dogs [59, 60]. Raw diets also contain significantly less ingredients with anti-nutritional effects [6162].

Increased digestibility and better nutrition can result in an increase in overall health; it can improve not only an animal’s physical health, but also its behavioral and cognitive health. This has been demonstrated in both humans [63] and dogs [64, 65, 66].

There is also evidence of significantly improved dental health in animals fed a diet that includes raw meaty bones [67].

“Raw” does not automatically mean “dangerous”

Many of the current raw diet studies focus on unbalanced diets [68, 69, 70, 71]. Some use this as evidence to imply that raw diets are difficult or impossible to balance. However, balancing a raw diet is easier than ever; resources on raw diets continue to grow, and this information is easily accessible to anyone with an internet connection and the time and patience to adequately research diet requirements.

The potential consequences of nutrient deficiencies should not be dismissed, and there is reason to be suspicious of whether or not every pet owner will put in the effort necessary to research, balance, and feed an appropriate homemade diet [71, 72]. However, the idea that no owner is able to research and feed a balanced diet or that all raw diets are unbalanced is simply false.

For owners that are not prepared to balance a diet themselves, there are plenty of commercial raw diets that have been formulated according to AAFCO, NRC, and FEDIAF standards, and there are homemade raw diet recipes readily available that have been formulated according to these standards by veterinarians and other professionals [73, 74] or that have passed feeding trials, which are supposed to be the “gold standard” of analysing a diet [75].

Another major concern with raw diets is in regards to potential pathogenic organisms, like salmonella, E coli, or internal parasites. There are multiple studies comparing the amount of salmonella bacteria found in kibble fed vs raw fed dog’s feces. In one study, 16 dogs were fed a contaminated raw food meal, and 7 of those dogs shed salmonella bacteria in their stool for up to 7 days following the meal; none of the dogs were symptomatic [76]. Another study found that dogs fed raw diets were significantly more likely to shed salmonella in their stool than dogs fed other types of diets [77]. Yet another identified salmonella in 30% of the stool samples analyzed from dogs fed a raw diet [78].

However, the frequency of fecal isolation of salmonella in healthy non raw fed dogs has been shown to be as high as 36% [79], indicating that this is not exclusive to raw fed animals. Further, fecal isolation of salmonella doesn’t directly translate to a higher risk of salmonella – all it means is that the animal has successfully passed salmonella bacteria without becoming symptomatic. The ability to harbor and pass salmonella as a normal, nonpathogenic bacteria is a known trait of carnivores [80].

Other studies have identified the presence of pathogenic microorganisms in commercial raw foods. One study found that 7% of the 60 commercial raw diet products analyzed tested positive for salmonella [81]. Another study analyzed 240 commercial raw food samples and 42 processed food samples (24 dry, 24 canned); about 6% of these samples tested positive for salmonella (all of which were raw foods), and 53% of these samples tested positive for E. coli (including both raw and processed foods) [82].

This is not exclusive to raw pet food products. Salmonella and other harmful pathogens have been found in dry foods [83] and dog chews and treats [84, 85]. There are many documented cases of humans obtaining salmonella from dry and canned pet foods [86].

The risk of internal parasites can be virtually eliminated by freezing raw meat before feeding, not feeding guts or intestines, and avoiding meats that have the potential to be infected with freeze-resistant parasites (such as polar bear or walrus).

Dogs, cats, and ferrets are equipped to handle much larger loads of bacteria in the diet [87], so the risk of salmonella or other bacteria is mostly a concern for the humans in the household rather than the pets. By practicing safe meat handling and sanitation when preparing raw foods of any kind – for consumption by pets or humans – the risk of salmonella to humans in the household can be greatly diminished.

Owners should also continue to use care when handling and disposing of feces to prevent contamination. Of course, this is also not exclusive to raw pet food or raw fed pets, but applies to the handling of any kind of pet food or waste. However, care should be practiced with raw diets, and owners should consider any potential risks. Greater care should be used if there are any small children, elderly, or immunocompromised in the household, or if the animal to be fed a raw diet is immunocompromised and/or has a history of bacterial overgrowth in the gut.

Conclusion

While kibble diets are convenient and cost effective for the average pet owner, more and more owners are beginning to consider more than just convenience and cost when choosing a diet for their pets. Pets are increasingly seen as members of the family to many owners, and their health and longevity is of utmost importance now more than ever before.

Thus, the number of owners choosing to feed raw continues to grow – with or without the support of their veterinarian. Many of these pet owners report that they have a low amount of trust in veterinary advice, not only with respect to nutrition, but also in general [88]. By bridging the divide between veterinary professionals and raw feeders, we can address this distrust for the benefit of our pets.

A divide also exists within the veterinary community itself. There are those who take a stance of strict opposition to raw food diets [89], but there are also those that actively recommend raw diets to their clients and report great success [90]. Many veterinary professionals acknowledge that they do not have adequate education on homemade or raw diets [91, 92], or feel that recommending a raw diet could be a liability if the owner does not take the proper sanitation precautions or ensure the are feeding a balanced diet, therefore – understandably – many vets do not feel comfortable recommending these diets to their clients.

However, rather than approaching this issue with strict opposition despite the growing evidence of the positive aspects of raw diets, veterinary and other pet care professionals should instead advocate for more evidence based, scientifically sound resources to be made available – to pet owners and professionals alike – regarding how to make sure the diet they are feeding is balanced and safe.

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9 comments

  1. I love your articles Plear. But would you be so kind to take sustainability into account in one of your next articles?

    Sustainability is an ever growing “issue”. At the current growth rate of human protein demand we are bound to face problems in the near future, where protein demand will rapidly surpass protein supply. Next to the growing world population, increasing equity/prosperity (especially in large Asian populations) and thus consumption of luxury goods, (more) pets should eat high protein, human-grade diets?

    World-wide there are an estimated 220 mil. pet dogs and 220 mil pet cats and these pet populations are growing steadily. According to my calculations, world meat production would have to increase by 18%, if all dogs and cats would be fed 100% BARF (better said: Raw Meaty Bones) diets. With our current approach of food waste streams and agricultural techniques this is simply an impossible task. Not only is it nearly impossible to achieve this production of animal protein, it is absolutely impossible to achieve this kind of animal protein production in a sustainable way. Next to this, the increasing demand in human-grade meat products would significantly increase the amount of animal by-products, which (I know thoughts about this are VERY subjective and wide-ranging) are supposedly “low-grade” and have to end up somewhere. Bio-diesel?

    To me, raw food diets are at odds with sustainability and sustainability should be an essential part of the mindsets of pet owners. Next to what is “best” for pets, people should keep feasibility in mind.

    What are your thoughts on this?

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    1. This is a fantastic comment with a lot of great points about very real concerns. I have an article on more sustainable raw feeding practices on my to do list and I will get it published ASAP. There is too much on this subject to say in a comment, but keep your eye out for the article. In short though, I think sustainable raw feeding can be attained through educated owners. Raw feeding is an avenue by which raw “by products” can be used that may otherwise be thrown away, such as offal/organ meat, bones, heads, feet, and even some hides/fur/feathers (which contain roughage and microminerals!). Raw pet food doesn’t have to be human grade – but the reason most people choose to buy human grade for their pets is due to safety and quality concerns. If we had more regulations on pet grade/non human grade foods, I think that would solve quality concern issues owners have while also acting as an avenue to use the entire animal and prevent waste.

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      1. Thank you for your reply.

        I will admit, I am a nutritionist for a European veterinary (non-raw) petfood company and you are the the first proponent of raw feeding (that I have come across) with a non-biased mindset. You look at raw feeding from all aspects, instead of the mainstream “reasoning” of 99% of the people that feed their pets raw: “because it is natural, it is best for the animal”. You do not criticize EVERY single ingredient in processed petfood and do not make bold untrue claims about what is processed in kibbles and canned food.

        Keep up the good work!

        Looking forward to your sustainability article!

        Like

  2. Glad I found your blog. Professionally, I work with patients on changing their diets to combat/reverse chronic disease, by using a whole foods plant based diet. And for the exact same reason I became a BARF feeder for my two large dogs. While I have never fed kibble, I always used a combo of home COOKED and freeze dried foods, along with veggies and fruits, dairy and cooked eggs. One of my dogs developed clear evidence of leaky gut syndrome manifesting in skin yeast and allergies, and both dogs had weight management issues.
    I now feed a formula based on Ian Billinghurst, and make it a point to constantly educate myself about the BARF diet.
    All my dog’s allergies have completely resolved, and both have lost weight easily, while eating more.
    While I constantly read the science when it comes to human nutrition, I don’t need extensive science for my dogs. Luckily in the animal world we still have plenty of wild animals to observe, which, when eating and living in their natural habitat, don’t usually have to deal with obesity, bad teeth, diabetes or cancer.
    My vet and his practice colleagues are amazed at how my dogs look (teeth especially), and the fact that one of them has completely healed with diet alone. Of course this is no surprise to me what so ever, since I see this in humans every day.
    Thanks for your terrific articles.

    Like

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