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InFocus

Fact-checking the latest trends in pet nutrition

With a wealth of animal nutrition information available alongside the increasing role of social media as a source of pet care information, what nutrition myths can veterinary professions help to dispel?

Clients are becoming more concerned about their pets’ diets, and social media, rather than veterinarians and breeders, has become their main source of information. Thousands of websites recommend what to give or avoid in pet diets. Some are very good, while others are managed by people with few or no qualifications and can spread misinformation. Moreover, marketers have been surfing on those trends. To effectively manage owners’ inquiries, practitioners must understand the facts behind the myths. So, let’s review some of the current nutritional beliefs and challenge them against the facts.

A “natural” diet?

Myth 1: “Natural” qualifies a healthier, more nutritious diet that respects the environment and promotes longevity

But what exactly is a “natural” pet food?

The term “natural” is not defined in the pet food regulations, but there are labelling guidelines for pet food manufacturers about how to use the claim “natural” (AAFCO, 2024; FEDIAF, 2019).

According to the European Pet Food Industry Federation (FEDIAF, 2019), the term “natural” should only be used to describe pet food components to which nothing has been added, and which have only been subjected to enough physical processing to make them suitable for pet food production, while maintaining their natural composition. This use is very restrictive, excluding several processing steps required for the manufacture of a complete and nutritionally balanced product. However, for some pet owners, the term “natural” has a different meaning and they automatically associate it with healthy diets.

Lifespan in nature – for wolves and wild cats – is short compared to the lifespan of pets. Indeed, the purpose of a “natural” diet (prey) is not to promote a long life, but a life long enough to allow reproduction. Natural diets should thus not be expected to promote longevity.

Myth 2: The “natural” diet of dogs and cats is meat, including the biologically appropriate raw foods (BARF) diet, the wilderness diet or diets with meat as the first ingredient

Wolves and cats have evolved on a natural diet consisting of prey, which is not synonymous with meat. Indeed, prey contains not only meat (striated muscle) but also bones (source of calcium, phosphorus and magnesium), brain tissue (rich in the omega-3 fatty acid DHA) and viscera (rich in vitamins, trace elements and taurine) (Davies et al., 2019). Yet viscera are qualified as “by-products” on pet food labels and decried by influencers and pet food marketers alike.

Researchers at the University of Ghent found that cheetahs fed whole rabbits had improved gastrointestinal health than when fed meat supplemented with minerals and vitamins (Depauw et al., 2013). The study suggested that the coat of prey acts as an “animal fibre” promoting the transit of food in the intestine and reducing colonic protein fermentation (putrefaction), which produces nitrogen metabolites that can be toxic (Depauw et al., 2013).

Eating prey provides wolves and wild cats a “complete and balanced diet”, ie a diet that contains all the nutrients in the right proportions. This is not the case with many BARF diets and recipes that have been reported to induce calcium deficiency and spontaneous bone fractures. Moreover, raw meats can be contaminated with pathogenic bacteria that are of concern for humans, especially young, immune-suppressed and elderly people, and thus for public health authorities (Davies et al., 2019).

There is evidence that dog domestication occurred as long as 33,000 years ago. Although the common ancestor of all dogs is the wolf, modern dogs have evolved to be very different in their shape and size, including the anatomy of their skull and jaws. They are less aggressive and endurant and have altered social and nutritional behaviour. A genetic study has shown that dogs carry more genes coding for amylases, the enzymes responsible for starch digestion, than wolves (Axelsson et al., 2013).

Further, another study in a remote area of Zimbabwe found that local wolves and village dogs did not compete for prey (Butler et al., 2018). Dogs were scavengers and ate whatever was made available to them by humans. Unexpectedly, investigators also discovered that their main source of protein was human faeces! The dogs were in good shape and reproduced normally.

In summary,modern dogs should be considered omnivorous and can thrive on a starch-rich diet. They are very different from wolves in feeding behaviour, relying on humans rather than on hunting.

What about digestible carbohydrates?

Myth 3: Prey contains little carbohydrate; thus, starch is not necessary and may have deleterious effects on dogs and cats, such as obesity and diabetes. Moreover, starch is a filler for cheap pet food

Neither dogs nor cats need carbohydrates in their diets; however, the brain, kidneys and red blood cells require glucose. Dogs and cats, like humans, can use amino acids to fulfil their glucose needs. This is called gluconeogenesis and is perfectly adapted for animals that ingest large amounts of protein and little carbohydrate, as in prey (Verbrugghe and Hesta, 2017). However, if an animal can digest starch, this is the most efficient way to provide glucose to the body. Moreover, protein becomes a limiting commodity for which animals and humans will soon compete. Wasting amino acids to produce glucose makes no sense.

As described above, the digestion and metabolism of starch by dogs is not an issue. Dogs are true omnivores. In cats, however, the transition from prey to cat food is less than 60 years old which is why the tolerance of cats to starch is the topic of heated debates between veterinary internists and nutritionists. Early work indicated that cats might not digest and metabolise starch efficiently; however, more recent studies support the fact that cats digest cooked starches nearly as efficiently as dogs. Cats are also able to adapt their metabolism to carbohydrate levels in their diet. Obesity and diabetes do not appear to be linked to carbohydrates but are clearly linked to fat and calories.

In summary, both dogs and cats tolerate starch well. If starches were not digested properly, this would result in excessive colonic fermentation and acute colitis (ie softer faeces with mucus and fresh blood), which is not what has been observed in the millions of cats fed commercial dry food.

Are grain-free diets the best?

Myth 4: Grains are a filler with little nutritional value, while carbohydrates are detrimental to carnivores, the quality of grains is poor and grains are a cause of allergy

Grains, and especially whole grains, are a source of valuable nutrients such as starch (a source of glucose), essential fatty acids (linoleic acid), protein, vitamins (vitamin E) and dietary fibres. Thus, grains cannot be considered as an ingredient of little or no nutritional value, as a filler would be. Moreover, producing grain-free kibbles requires other sources of starches such as potatoes, lentils, peas or tapioca, but with limited added nutritional benefits (Laflamme et al., 2014).

Quality pet food companies pay a lot of attention to the ingredients they use: a good product cannot be made with bad ingredients. Each ingredient has its specifications that are validated upon arrival at the plant. For example, with grain, special attention is given to the aspect and moisture of the grain, and whether insects, foreign bodies, mould or mycotoxins are detected. If the load does not fulfil these specifications, the truck is rejected (Laflamme et al., 2014).

Any source of protein can induce allergy; however, more animal than vegetable proteins have been linked to allergy. There is no evidence that dogs and cats suffer from gluten intolerance as in humans.

In 2018, the FDA posted an announcement linking some grain-free dog foods to dilated cardiomyopathy (DCM) (Haimovitz et al., 2022). Cardiomyopathy can be reversed in affected dogs when fed a more traditional diet. To date, the rationale for this association has yet to be determined and research is ongoing. The hypothesis is that high levels of certain ingredients used as starch sources (eg peas or lentils) could affect the absorption and/or metabolism of nutrients.

In summary, there are no demonstrated health benefits of feeding a grain-free diet, but long-term feeding of a grain-free diet may be associated with DCM in dogs.

Conclusion

Only some of the most important of the numerous beliefs and claims regarding pet food have been covered here. Confronting pet parents with facts can be challenging as social media reinforces their convictions. Asking questions such as: “How do you make sure that the diet of your pet fulfils all its nutritional needs?”, “How do you make sure that you and your family are not contaminated by bacteria when fixing a meal based on raw meat?” or “Has a nutritionist formulated the diet?” can induce doubt and help steer the client to proven diets with quality control.

Both the World Small Animal Veterinary Association and American Animal Hospital Association offer nutrition toolkits that may help practitioners with these important conversations and promote better client understanding.

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