Natural Pet Diets - A Scientific Exploration
In this post, we look at a recently published review of natural pet foods,(1) ("the Paper") and dive deep into the benefits of feeding your cats and dogs a diet that aligns with their instincts and ancestral preferences.
From improved digestion to better overall health, discover why more pet parents are turning to minimally processed, whole food options.
We also consider commonly regarded pitfalls and risks associated with natural and raw diets and the importance of striking a balance between nutrition, sustainability, and safety. Enjoy!
Want to listen to the podcast episode instead? Listen here.
What is a natural pet diet?
Natural pet diets can be referred to as instinctual or ancestral (also referred to as species appropriate / evolutionary). This type of diet is based on the animal’s physiological capabilities or preferences, rather than simply meeting a regulatory definition of natural pet food.
An Instinctual diet is regarded as one where companion animals are fed a diet according to their innate preferences.
An Ancestral (or species appropriate or evolutionary) diet is regarded as one where companion animals are fed a diet similar to their evolutionary ancestors.
These diets assume alignment with the physiological needs and metabolic capabilities of companion animals.
What is natural?
When it comes to natural pet food, there can be variations on what that actually means. Between individuals (pet parents, vets and other animal health professionals, pet food manufacturers, etc), and even between the two main pet food regulators - AAFCO and FEDIAF.
According to AAFCO (the Association of American Feed Control Officials) - a voluntary member association of state feed officials with the responsibility of developing model regulations for animal feeds and drug remedies - natural pet food means:
...A feed or ingredient derived solely from plant, animal or mined sources, either in its unprocessed state or having been subject to physical processing, heat processing, rendering, purification, extraction, hydrolysis, enzymolysis or fermentation, but not having been produced by or subject to a chemically synthetic process and not containing any additives or processing aids that are chemically synthetic except in amounts as might occur unavoidably in good manufacturing practices.(2)
FEDIAF, the European Pet Food Industry Association regards natural, with reference to pet food, as being a term that "should be used only to describe pet food components (derived from plant, animal, microorganism or minerals) to which nothing has been added and which have been subjected only to such physical processing as to make them suitable for pet food production and maintaining the natural composition".(3)
The two main differences in these definitions is the use of chemical processing aids. AAFCO allows them, FEDIAF doesn’t.
The Paper gives some helpful examples:
AAFCO would allow hexane-extracted soybean oil because hexane is not present in the final ingredient except in amounts that might occur unavoidably in manufacturing. (nb hexane is a colourless liquid that can have a petroleum like odour - it’s a chemical made from crude oil)
FEDIAF would not allow hexane-extracted soybean oil because it uses chemical extraction.
AAFCO may allow carotene (a pigment found in plants) extracted from carrot pulp. FEDIAF wouldn’t consider this a natural ingredient because the natural composition has changed.
FEDIAF excludes genetically modified ingredients. AAFCO is silent on it.
Does the research support natural pet diets?
I’d like to start off by saying that research is dictated by the person, industry or organisation that wants it performed. On many occasions, research is performed to support claims that a pet food producer wants to make, so it can be biased. As a result, there exists significantly more research supporting processed pet foods than there is natural pet foods.
But this doesn’t mean that there isn’t any research that speaks to the advantages and disadvantages of feeding a companion animal natural pet food.
The Paper reviews some of this research, as shown below:
Natural Diets
Instinctual Diets:
Dogs of various breeds select a macronutrient profile in which 30% of their ME, their metabolisable energy (the amount of energy in animal feed minus the energy lost in faeces and urine), comes from protein, 63% from fat and 7% from carbohydrate.
Cats select 52% of their ME from protein, 36% from fat and 12% from carbohydrate.
Observations:
Cats have a higher preference for protein in cats compared to dogs. This is supported by the cat’s obligate carnivore status. Dogs prefer higher levels of fat compared to cats.
Most processed pet food contains significantly higher levels of carbohydrates than what a cat or dog is instinctually driven to eat. Dry food especially will usually contain up to 60% carbohydrate.
Ancestral Diets:
It is recognised that domestic dogs evolved from wolves.
Key genes of domestic dogs compared to wolves have mutated to support an increased ability to digest starch.
Analysis of 50 diets consumed by wolves showed an average nutrient intake of 52% ME from protein, 47% from fat and 1% from carbohydrate.
The domestic cat is most closely related to the European wildcat (Felis silvestris), the African wildcat (Felis libyca) and the sand cat (Felis nigripes).
The natural diet of feral cats consists primarily of small mammals, birds, fish, reptiles, and invertebrates with a macronutrient profile of 52% ME from protein, 46% from fat and 2% from carbohydrate.
Studies on the preferred macronutrient profile of domestic cats reveals that domestic cats and wild cats share instinctual dietary preferences.
The digestibility of raw meat diets is similar between domestic cats and cheetahs. Other research shows that there is similarity in total tract crude protein digestibility between domestic cats and African wildcats and jaguars.
Observations:
The Paper refers to research that dogs descended from a subset of wolves that had greater socialisation with humans. This increased contact with humans has seen the development of omnivorous tendencies in contrast to carnivorous wolves. Dogs can have their nutritional requirements met from plant sources as well as animal sources.
If we review the ME percentages of the instinctual diets and the ancestral diets for dogs and wolves, we can see that wolves have a higher preference for protein and fat compared to domestic dogs, and a much lower preference for carbohydrate.
There is similar protein preferences between domestic cats and wild cats but domestic cats seem to have a higher preference for carbohydrate compared to wild cats but not in comparison to the natural diet of feral cats.
Just because the domestic dog has an increased susceptibility to digest starch, does this mean that it is beneficial for them?
Research looks at a subset of animals within a set of certain circumstances, not at the individual. Some do well with starch some don’t. It's important to take the individual animal in to account when determining the best and healthiest diet.
Metabolism:
Both dogs and cats have the ability to digest carbohydrates.
Cats have a lower ability to digest carbohydrates compared to other species.
Even though cats have the ability to digest carbohydrates, their capacity for carbohydrate digestion may be limited. This is evidenced by digestive disorders such as diarrhoea, flatulence and bloating when high amounts of carbohydrates are fed (>5g/kg body weight).
Dogs have a greater capacity of fat oxidation compared to humans.
Dogs share a similar glucose response to humans when carbohydrates are consumed.
Dogs had a delayed peak glucose concentration and sustained glucose response when fed a high protein (49%), low carbohydrate (13%) diet compared to when they were fed a lower protein (22%), higher carbohydrate (45%) diet.
Both higher carbohydrate and lower carbohydrate diets can reduce insulin sensitivity in cats.
Higher concentrations of dietary fat (51% compared to 33%) reduces glucose tolerance in cats.
A higher protein diet has shown to be beneficial for dogs who are obese and for increased exercise performance.
Observations:
Cats have difficulty digesting carbohydrate compared to dogs and humans.
Dogs digest fat better than humans.
There are similarities between the glucose response of dogs and humans when carbohydrate is consumed.
Dogs have a steadier glucose response when they eat a higher protein, lower carbohydrate diet.
Fat and carbohydrate are relevant to glucose tolerance in cats.
The Paper, in reviewing the studies on metabolism, provides a beneficial summary supporting the alignment between feline and canine physiological and metabolic capabilities with instinctual nutrition, particularly when the animal is under stress, such as from aerobic exercise.
Whole vs isolated ingredients
Pet foods are generally formulated around specific nutrient requirements rather than the ingredients themselves. But many pet parents are seeking out whole food options for their companion animals. Holistically inclined animal health professionals are advocating a whole food diet for companion animals.
The Paper refers to an AAFCO definition that defines “whole”, as it it pertains to pet food ingredients, as a “physical form that is ‘complete’, entire’”.
In terms of commercial pet foods, there is a tendency in pet food processing to isolate specific parts of an ingredient, rather than incorporating the whole ingredient, and stabilising an ingredient by adding synthetic preservatives. According to the Paper, AAFCO would consider fractionated or isolated ingredients as natural, but not the synthetically preserved ingredients.
Pet parents might not agree, instead regarding fractionated preserved ingredients as unnatural. But those seeking a whole food diet for their companion animal would certainly agree that synthetically preserved ingredients are not natural.
The Paper speaks to the food synergy benefits of feeding whole foods - that a food as a whole can have greater health benefits than its isolated or fractionated parts.
Within plant foods specifically, the whole grain itself, which includes the fibre, vitamins, minerals and phytonutrients has greater health benefits than feeding refined grains. In processed pet foods, you will often see isolated grain components. This tells you that refined grains, or isolated parts, have been used rather than the whole foods, for example, corn gluten meal instead of the whole corn.
Like to do more some more label analysis? Check out the Decoding Pet Food Labels masterclass. If you're a details person or a food nerd, you'll absolutely love it. Get it here.
One study the Paper refers to that I find really interesting is a study on roosters by Cramer et al. In this study, roosters were used to measure true amino acid digestibility of rendered animal meals vs raw animal products.
Nb. Rendered animal meals are heat treated and physically transformed animal by-products destroying pathogens, removing moisture, separating solids and lips or fats oils to provide “valuable animal protein meal” or processed animal protein, and rendered fat/oil.
The study found that the rendered animal meals had lower amino acid digestibility compared to raw animal products, with lamb meal having the poorest amino acid digestibility and pork livers having the greatest. In another study, rendered poultry had a negative influence on ileal digestibility in dogs, but rendered beef didn’t.
Nb. "Ileal" is the third portion of the small intestine. "Digesta" means something undergoing digestion. "Ileal digestibility" refers to the amount of amino acids ingested vs the amount recovered from the digesta in the ileum. It indicates the bioavailability of amino acids.
Ingredient processing and product processing
The Paper looks at the effects processing can have on nutritional value.
Gelatinisation of wheat starch is associated with improved digestibility.
Gelatinisation of starch and reactive lysine increased with extrusion temperatures up to 150°C vs untreated control.
Increasing the time of heat treatment during canning of cat food was associated with reduced digestibility in rats.
Higher drying temperatures (200°C) of an extruded canine diet resulted in lower lysine, reactive lysine, reactive to total lysine ratio, linolenic acid, and linolenic acid concentrations compared to lower drying temperatures (≤160°C) in 4mm kibbles.
Feeding diets containing 73% moisture reduced the calcium oxalate relative super saturation compared with 6 and 53% moisture diets. The higher moisture diet also reduced specific gravity compared to the 6, 25 and 53% moisture diets.
Ingestion of a 40% hydrated diet compared to a dry diet with 12% moisture caused cats to eat less, gain less and have an increased activity level.
Total tract digestibility was found to be greater in raw and cooked beef based diets compared to extruded diets. There was no difference in apparent digestibility between the raw and cooked beef based diets.
Nb. Gelatinisation is the heating of starch granules, causing them to swell and burst.
Extrusion is a cooking process used in the manufacturing of about 95% of dry pet foods
Observations:
The Paper observes that “from a nutritional perspective, foods with moisture content similar to animal prey would better align with a natural pet nutrition philosophy compared to dry foods”.
The Paper observes that there is limited evidence that demonstrates health benefits of high dietary moisture intake in dogs, but there have been demonstrated effects in feeding cats a higher moisture diet with regard to urinary tract health and weight management. Further, the Paper states that “Although these findings may be specific to the diets evaluated, given the ubiquitous nature of urinary related syndromes in cats, the potential health benefits of feeding pet food with higher moisture content (e.g., pasteurized/ refrigerated, raw, frozen, or canned) that typically contain 70 to 85% moisture should be noted.”
Feeding a natural diet (as opposed to a commercial processed diet) has numerous benefits with regard to the moisture levels found in natural diets, including feline urinary health and digestibility.
High protein and environmental sustainability
Interestingly, the Paper considers the pros and cons of feeding higher protein, lower carbohydrate diets with reference to environmental stability.
The authors refer to research that speaks to the negative impacts on the environment when feeding high animal based protein diets to companion animals, and that “including carbohydrate in pet foods aligns with the concept of nutritional sustainability by reducing the environmental impact of pet foods while supporting pet health and nutritional needs… the potential health benefits of feeding natural diets, specific to an individual pet’s lifestyle and health status, should be weighed against the potential health and environmental concerns of feeding a natural diet high in protein and fat”.
Whilst I agree wholeheartedly with taking environmental sustainability into account, I don’t think this should be seen as a permission slip to feed companion animals high carbohydrate diets. There needs to be a balance between environmental stability and pet health and nutrition. Like all things in nature, we need to learn how to coexist.
Solutions around this might be to incorporate higher levels of plant foods in dog diets, but not to the extent of the high carbohydrate levels found in most commercial pet foods. It’s more challenging to reconcile this when it comes to cat diets, because of their need and preference for higher protein levels in their foods.
Risks of feeding raw
Raw food is demonised by many due to food safety issues, particularly with regard to pathogenic bacteria.
Studies have demonstrated that raw or undercooked animal-source protein may be contaminated with a variety of pathogenic organisms, including salmonella, campylobacter, clostridium, eColi, listeria and staphylococcus. According to the research, the presence of these organisms poses a risk of food borne illness to pets eating the contaminated food, and of secondary transmission to humans, especially children, older persons and immunocompromised individuals.
A study of 200 therapy dogs revealed an incidence rate of salmonella shedding in the raw meat fed dogs compared with the dogs who weren’t fed a raw meat diet.
Raw food diets can pose risk for metabolic disease depending on the parts of the animal used in the diet. For example, clinical cases of dietary hyperthyroidism have been reported in dogs fed bone and raw food diets, which was reversed by feeding commercial pet food.
The American Veterinary Medical Association, American Animal Hospital Association, and U.S. Food and Drug Administration have issued statements on the avoidance and safe handling practices of raw foods.
Observations: contaminated food - high quality
Dogs and cats can generally handle the bacteria in raw meat because of the consistent acidity of their stomach fluid.(4)
There is some caution against feeding pets a raw diet that may contain pathogenic bacteria if they have severe disease such as moderately advanced heart, kidney or liver dysfunction, diabetes or cancer.(5)
If safe food practices are used, raw meats should not harm the humans handling the food.
As far as "contaminated" food is concerned, seek out the highest quality you can afford eg human grave over pet grade, because human grade foods go through a more stringent regulatory process than pet grade foods.
Consider removing exposure to raw meats from children, older people and immunocompromised individuals.
Prominent holistic vet, Dr Jean Dodds, has published remarks on the risks for metabolic disease specific to the hyperthyroid study. She states that “Since none of the dogs in this report were being supplemented with L-thyroxine, the most likely cause of their high T4 concentrations and clinical signs of thyrotoxicosis was the feeding of a meat diet that had been contaminated with thyroid tissue…. In the dogs of this report, it is obvious that the correct balance [of the diet] was not maintained and a very large amount of raw thyroid gland tissue ended up in their raw meat diet”.(6)
What’s your take?
Perhaps you might like to consider:
What would you prefer to feed your pet? Think about the benefits associated with humans eating whole, natural foods instead of processed food. Is it any different for animals? If natural foods are healthier for us, wouldn't they similarly be healthier for all animals of other species?
What would your animal prefer to eat? According to the research, companion animals would prefer to eat a diet that more closely aligns with their instinctual or ancestral diet, and that's higher protein and higher fat compared to carbohydrate. Be careful of those kibble brands that say their food is high in protein and/or higher in protein than other brands. They might be higher in protein than other kibble brands, but they're still significantly higher in protein than what suits the instinctual or ancestral needs of cats and dogs.
Do we even need the research? Research will no doubt continue to evolve to support the research on natural human diets, and that is a good thing. But like me, perhaps you feel it in your bones that natural is better than processed for companion animals too.
Summary
A natural pet diet aligns with animals' physiological needs and ancestral preferences, focusing on minimally processed, whole foods. Research supports benefits such as improved digestion and nutritional synergy, particularly in high-protein, low-carbohydrate diets. Whilst there are concerns over bacterial contamination in raw diets, use the highest quality you can afford and use safe food handling practices. Balancing nutritional benefits, environmental sustainability, and safety considerations ought to be factors that pet parents take into account when choosing pet food.
References
1. Buff PR, Carter RA, Bauer JE and Kersey JH, ‘Natural Pet Food: A review of natural diets and their impact on canine and feline physiology’, J. Anim. Sci. 2014.92:3781–3791.
2. Association of American Feed Control Officials (AAFCO). 2013. Official Publication. Assoc. Am. Feed Cont. Off., Champaign, IL.
3. The European Pet Food Industry Federation (FEDIAF). 2011. Code of good labelling practices for pet food. Euro. Pet Food Ind. Fed., Brussels, Belgium.
4. Stogdale, L. ‘One veterinarian’s experience with owners who are feeding raw meat to their pets’, Can Vet J. 2019 Jun; 60(6): 655-658.
5. Ibid.
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