Convenient, affordable, and with a long shelf life, products like kibble and canned chow have long dominated the pet food market – but with chronic animal diseases on the rise, could ultra-processed pet food be to blame?
The Nova food classification system groups foods, beverages, and culinary ingredients into four categories based on how much processing they have undergone. Exclusively used to evaluate human nutrition, Nova ranges from minimally processed (group 1, including foods such as fresh fruits and vegetables) to ultra-processed (group 4, including products like energy drinks and most ready meals).
Since the system was first proposed in 2009, it has grown in popularity not only among academics who have used the scale in both experimental and epidemiological research to discover strong links between UPF-heavy diets and a range of adverse health outcomes, but also among nutritionists and public health institutions. The Pan American Health Organization (PAHO), for instance, has adopted the system in its nutritional guidance.
No such system currently exists for pet food, but some nutritionists and researchers think this should change. Fi Global Insights spoke to Dr Donna Raditic, a board-certified veterinary nutritionist and founder of Nutrition and Integrative Medicine Consultants, who is championing this approach.
“For pets, we don’t have a formal system, but we should,” says Raditic. “Something similar to the Nova system applied to pet food [would] help people understand what they’re feeding their pets.”
In a 2021 journal article, she suggests as a starting point a pet food categorisation system which makes a distinction between ultra-processed commercial diets (UPCD) consisting of “dry, canned, and any other pet foods that are manufactured using more than one thermal or pressure processing step to produce the final product”, and minimally processed commercial diets (MPCD), defined as “fresh, frozen, and any pet food manufactured with no or only one thermal or pressure processing step”.
At minimum, a Nova-style pet food system would allow pet nutrition researchers a framework to conduct more research into the subject.
“There’s very little published research comparing different types of pet diets,” says Raditic. “We know a lot about individual nutrients – calcium, phosphorus, magnesium – but we don’t have many well-designed studies that compare whole diets, like commercial raw versus kibble.”
While recent research has shown the growing proportion of UPF in the human diet – more than half of all caloric intake in countries like the UK – if the same standards are applied to pet food, most of our animal companions have relied on ultra-processed products as the primary source of nutrition for many decades.
Raditic explains that most commercial dry foods use a processing technique known as extrusion, where ingredients – including some that may have already been processed like dry meat meals, grains, and fats – are mixed, cooked, extruded, heated again to remove moisture, then coated with flavourings obtain the final product.
This process has made pet food affordable and shelf-stable, but some recent studies suggest it could also have adverse effects.
The DogRisk research group, based at the University of Helsinki in Finland, has conducted several studies comparing the effects of an ‘ultra-processed carbohydrate-based diet’ (UPCD) with a ‘non-processed meat-based diet’ (NPMD) on health outcomes in dogs.
A 2023 study published in the journal Frontiers found that dogs that ate NPMD during pregnancy, or in early and late postnatal life, had a reduced risk of otitis (a common form of inflammation affecting the ears) later in the dog’s life compared to those on a UPCD diet. The authors noted that further research is required to understand what drives this causal connection.
Another study from last year, published in Nature, looked at the role of dogs’ diets on the likelihood of developing chronic enteropathy – a gastrointestinal disorder similar to the human inflammatory bowel disease. The paper concluded that puppies that ate NPMD, human meal leftovers, and table scraps – especially berries, raw bones, and cartilage – were much more likely to avoid any incidence of bowel disorders. An exclusively ultra-processed diet consisting of kibble and rawhides, on the other hand, was a major risk factor for chronic enteropathy.
Raditic is convinced that these studies are only exposing the tip of a large iceberg of health issues, pointing to the recently discovered connections between UPF consumption in humans and the rise in a variety of chronic health issues.
“Many of the chronic diseases we see in humans are now becoming common in pets – things like chronic kidney disease, gastrointestinal issues, and cancers,” she says. “These are diseases which we are learning in human studies are associated with diets high in UPF. Where we once were treating infectious diseases in pets, today it is primarily chronic diseases that are considered food-related in human medicine.”
While some of the most cited negative vectors of UPF consumption in human diets such as hyperpalatability and excessive salt, sugar, and saturated fat intake might not be as relevant in ultra-processed pet food – which tends to be formulated with a complete and balanced nutritional profile – there are other concerns that are more significant for pet food than human food.
A frequently cited concern is the introduction of advanced glycation end products (AGEs), compounds that form when proteins or fats combine with sugars in a process known as the Maillard reaction, which is often triggered by heat treatments like frying, grilling, and baking.
A 2020 study published in the journal Comprehensive Reviews in Food Science and Food Safety explored the link between processing and dietary AGE formation. The study found that these dietary AGEs can accumulate in the body when absorbed through the gastrointestinal tract, contributing to oxidative stress, inflammation, and the development of chronic conditions like diabetes and cardiovascular disease.
While the bioavailability of dietary AGEs and their ability to fuel biological AGEs in the body remains debated, evidence suggests that processed foods, especially those cooked at high temperatures, significantly increase the intake of these harmful compounds, potentially worsening health outcomes.
What’s more, some of these AGEs are present in much higher doses in pet foods than human foods. One study found that on a metabolic body weight basis, the amount of the AGE, hydroxymethylfurfural intake, was 122 times higher among dogs eating extruded commercial dog foods and 38 times higher among pet cats than adult humans eating a Western diet.
Despite the emerging science and growing consumer concerns, regulation in the pet food industry is not yet informed by AGEs or ultra-processed classifications. Current regulations focus on ensuring that pet foods are free from pathogens and that they are nutritionally "complete and balanced" – but they are not evaluating other potential health effects of commercially processed pet foods.
Not all nutritionists are convinced that the ultra-processed label is relevant when assessing pet food. In an article published in the same edition of the journal that featured Raditic’ proposed categorisation system, Dr Sanderson – an associate professor at the college of veterinary medicine in Georgia who has received research funding from commercial pet food companies Hill’s and Nestlé Purina – offered a contrasting opinion.
“Commercial pet foods are processed, as are essentially all the foods humans consume, and commercial pet food, which is a complete and balanced diet, currently does not fit well into the classification of ultra-processed foods,” she writes, arguing that the characteristics of human UPF products – high energy density, high amount of sugars, unhealthy fats, and salt, and low amounts of dietary fibres – are not typical of commercial pet food.
Nonetheless, Raditic advocates for greater transparency in pet food manufacturing.
“Independent researchers should be doing studies that compare different whole diets and their effects on the health of pets, evaluating AGEs, and other harmful byproducts of processing perhaps developing a research-based health index for pet foods.
“We need to make this information available to consumers,” she says. “This would help consumers make informed choices, but the big pet food companies are unlikely to lead this change they’re too entrenched in the status quo."
