Commercial Fresh Pet Food Diets

Pet humanization is here to stay as today’s clients no longer view their pet as “just an animal” and now consider pets as family members. The largest percentage of pet owners is composed of millennials (33%), followed by Gen X (25%) and baby boomers (24%), and their preferred label is “pet parents.”^1,2 Today’s clients strive to help their pet be healthy and live longer by exploring what they are putting into the food bowl.

An array of new diet types is entering the pet food market, but the one that seems to be getting a lot of attention is fresh pet food.^1-3 Although sales of conventional dry pet food still dominate the pet food market, growth has been slow at 2% to 4% compared with 20% for other pet food types (e.g., freeze dried, baked, air dried, fresh).³ A recent report defined “fresh pet foods” as pet foods typically consisting of minimally processed, whole ingredients delivered in a ready-to-serve format.³ Fresh pet foods are often refrigerated or frozen to maintain freshness. They appeal to clients who want to offer their pets a diet akin to homemade meals.³

Food Categorization and Processing

In addition to pet humanization, the authors believe that clients’ growing interest in fresh pet foods is being driven by media and articles about the role of ultraprocessed foods (UPFs) in human health and disease.^4,5 Consumption of highly processed foods has increased exponentially over the decades. To understand the effects of processed foods on human health, a food classification system, called Nova, evolved to describe the effects of diet on human health.⁶ The terms “ultraprocessed foods, processed, and minimally processed foods” were defined by the Nova system and applied to foods and culinary ingredients according to the nature, extent, and purpose of industrial processing.⁶ Many epidemiologic studies that used the Nova system have produced evidence from 45 meta-analyses that encompass almost 10 million human study participants.^7,8-11 They found direct associations between exposure to UPF and 32 health parameters in humans (e.g., cancer; metabolic syndrome; mental health; respiratory, cardiovascular, and gastrointestinal diseases; death). That finding was quantified in a pooled analysis of 7 cohorts that showed that a 10% increase in UPF consumption is associated with a 12% (95% confidence interval, 1.11 to 1.13) higher incidence of type 2 diabetes.^7,8 Currently, some countries use the Nova system and its UPF descriptor to update and develop human nutrition guidelines and nutrition policy actions.^7,8,12

In the food industry, much attention has been given to thermal processing because not only does it improve food safety and shelf stability but it also improves flavors and textures via the Maillard reaction.¹³ The Maillard reaction is a nonenzymatic reaction between amino acids and sugars in foods, which forms compounds that improve flavors, smell, and taste. The negatives of the Maillard reaction are that it also forms compounds known as dietary glycotoxins, or advanced glycation end-products (AGEs).¹³ Research is demonstrating that absorption of dietary AGEs and their accumulation in the body may affect age-related diseases in humans and animals.^13-19 A well-known AGE in UPF is acrylamide, which is monitored by the Food and Drug Administration (FDA) because animal studies have demonstrated an association between high acrylamide intake and cancers.^20,21 In experimental animal models and human studies, other AGEs have been associated with age-related diseases (e.g., atherosclerosis, nephropathy, retinopathy, osteoarthritis, neurodegenerative diseases, diabetes mellitus).^13-19 To promote human health and prevent chronic disease, limiting intake of UPFs containing high amounts of AGEs is recommended.^15,20-24

At present, the pet food industry has not adopted a type of feed or ingredient classification system describing level of processing. Based on human nutrition research, the authors believe that implementing a Nova-like classification for pet diets and their ingredients could advance our understanding of the processing effects in companion animal nutrition research. Currently, determining the healthiness of different pet food types is difficult. Based on the authors’ evaluations of AGE studies in human and pet foods, the authors believe that fresh pet food diets that use fewer processed whole-food ingredients and less thermal processing to produce the final products would be considered less processed or minimally processed according to a Nova-like system and should contain fewer AGEs. This may be an advantage for fresh pet foods compared with traditional dry and canned diets, but more research is needed on different pet food processing, AGE levels in pet diet types, and their effects on pet health.

UPF and AGE Research

As the research about human UPFs and AGEs reaches popular media, clients are asking about the healthiness of the pet foods they are feeding. According to the Nova system, a typical example of UPFs in human food is ready-to-eat breakfast cereals.⁶ In the 1950s, the Ralston Purina company, which produced Chex cereals, applied similar processing methods to develop dry dog food²⁵; therefore, dry pet food would be considered UPF under the Nova system.

Furthermore, similar to AGE studies of human food, AGE studies of pet foods have measured AGEs in the foods and in dog and cat biofluids. One study measured AGEs in 67 dry, canned, and pelleted dog and cat foods for growth and maintenance.²⁶ The researchers estimated that the average daily intake of an AGE on a mg/kg metabolic body weight^0.75 basis was 122 times higher for dogs and 38 times higher for cats than the calculated average daily intake on a mg/kg metabolic body weight^0.75 basis for adult humans.²⁶

Oba et al measured AGEs in 53 dry and canned dog foods, dog treats, dry and canned cat foods, and cat treats and demonstrated that AGE concentrations in pet foods and treats varied. ²⁷ They concluded that “it seems logical that high AGE intake over a long period of time may have negative effects on pet health.”

Another study measured AGE levels in traditional dry and canned cat diets and in urine from cats fed those diets and reported increasing urinary AGE excretion with increasing dietary AGE intake.²⁸ A study that evaluated urinary AGEs in privately owned dogs and cats fed differently processed diets found that urinary AGEs in dogs fed dry food were 2 to 3 times higher than in dogs fed raw (minimally processed) diets and that cats fed raw food diets excreted less AGEs than cats fed traditional canned plus dry food or dry food only.²⁹

Bridglalsingh et al evaluated plasma and urine AGEs for the dogs consuming 4 differently processed foods.³⁰ They reported that plasma AGEs were significantly higher when the dogs consumed canned food, whereas urine AGEs/mmol/creatinine were highest when the dogs consumed dry food. Elevated levels of AGEs have been found in tissue proteins of dogs with cataracts, osteoarthritis, cognitive dysfunction, vascular dysfunction, atherosclerosis, and skin collagen with increasing age.^31-35

A 2017 survey conducted by Nestlé Purina PetCare Company found that 84% of pet owners are concerned about the ingredients in their pets’ food.³⁶ More than 4 out of 5 pet owners are likely to read the list of ingredients in a pet food before buying it,³⁶ which is similar to a human parent trying to evaluate infant formulas.

Infant formulas are complete and balanced (i.e., claiming to provide total nutrition for the first 6 months of life), similar to the Association of American Feed Control Officials (AAFCO)-approved growth diets that claim to provide total nutrition for a growing puppy or kitten. As with adult foods, there are also studies and concerns with AGE content of ultraprocessed infant formulas and effects on infant health.^37-42 Although infants will grow and transition to eating a wide array of both processed and unprocessed foods, most puppies and kittens will eventually be fed adult maintenance ultraprocessed dry or canned foods as the major source of nutrition for their entire life.

Human-Grade Claim

Another potential positive of fresh food diets and other diet types is the human-grade labeling claim for pet foods approved by AAFCO in 2022.⁴³ The U.S. Department of Agriculture (USDA) requires that food for human consumption be officially edible and deemed safe for humans, meaning that the food must be produced according to FDA guidelines.⁴⁴ Before approval of the human-grade labeling claim, what we typically call “pet food” is defined by the USDA as “feed,” which can be made from animal and plant ingredients that are not fit for human consumption, also called “human inedible.”^43,44

To use the human-grade claim, pet food manufacturers must document that all ingredients are fit for human consumption. This means that all ingredients and finished products are stored, handled, processed, and transported in compliance with current good manufacturing practice for human foods (Title 21 CFR Part 117)⁴⁴ and that manufacturing facilities are licensed by appropriate local, county, or state public health authorities to produce human food. Facilities that process or package ready-to-eat, human-grade pet food products must be registered as both FDA food facilities and FDA feed facilities.⁴⁴ Although it is possible to make processed pet foods such as extruded kibble and canned diets by using human-grade ingredients, most industrial manufacturing facilities do not fit that claim.

Disadvantages of Fresh Pet Foods

There may be some practical disadvantages of fresh pet foods.⁴⁵ Purchasers need to consider the space needed for refrigeration and freezing and, of course, sustainability and short shelf life (compared with the long shelf life and easy scooping of dry food or the convenience of opening canned food).⁴⁵

Additionally, some fresh pet foods are subscription based. Concerns about the environmental effects of transporting and storing fresh or frozen diets have been discussed.⁴⁵ In discussions of sustainability, shelf life, and environmental effects of human UPFs compared with minimally processed foods, the counter argument is the potential cost benefits of limiting human UPF intake on the healthcare and welfare systems.^7-9 The effect on human health care is a counterargument because of the vast amount of evidence of the association of high UPF intake and chronic disease states, which has not been thoroughly investigated in veterinary medicine.⁷

To compare the costs of different types of pet foods (TABLE 1), it is most accurate to calculate the cost of diets per 100 kilocalories as pet food companies use different bag, can, and container sizes. Fresh pet foods fall into the expected cost range of feeding canned over-the-counter and veterinary therapeutic diets, which is logical because of the water content in those diet types (i.e., about 10% moisture in dry foods compared with 75% moisture in canned and fresh pet foods).

.

Summary

In the authors’ clinical experience, clients trying to understand and seek healthier pet diets are asking about commercial fresh pet food diets. They want to understand the AAFCO human-grade labeling claim, the UPF concerns, and studies of food processing and dietary AGEs, which are now in the media. Given the published data that processed foods will potentially contain high levels of harmful AGEs, it is imperative to investigate the potential detrimental health effects of pet food processing along with possible benefits of minimally processed pet diet types such as fresh pet foods. Veterinarians should understand and be prepared to provide accurate information regarding the potential advantages and disadvantages of fresh pet foods compared with traditional dry and canned diets.