Pet Nutrition Myths: A Review of the Facts

Many pet parents today are interested in learning about optimal nutrition for their furry loved ones, and the first place they seek answers is often on the internet. Unfortunately, there are a variety of blogs and courses published online that may disseminate inaccurate or biased information. There is a lot of information out there, so how does one sort out fact from fiction? While nutrition science isn’t perfect, it’s the best approach we have to figure out how to best feed our pets. The following review is an evidence-based approach to some common myths found online about pet food and the pet food industry.

Myth #1: The first two protein sources in a recipe should be from animals and not plants

There is no nutritional evidence in the literature to substantiate this claim. Scientifically, it is not about the ingredients – it is about the nutrients the ingredients provide. Essential amino acids can be provided by both plant and animal proteins. The diet in its entirety and the nutrients provided by the ingredients are more important than the ingredient order and source.

Myth #2: High quantities of plant-based protein sources is indicative of a low digestibility food

Plant-based proteins may be somewhat less digestible than animal protein sources; however, without digestibility trials comparing specific recipes, this statement cannot be substantiated. Pet foods contain a variety of different protein sources which are used to provide adequate amounts of essential and non-essential amino acids.

It is crucial to understand that animals don’t require specific protein sources; rather, they require adequate levels of specific amino acids, which can be supplied by both plant and animal proteins. The body does not differentiate whether the amino acids came from plant- or animal-based ingredients.

Petcurean TeamA Team of Dedicated Pet Parents + Nutrition Experts

Both animal protein and plant protein sources have advantages and disadvantages that pet food formulators must consider when developing a diet.

Animal proteins provide a high-quality balance of amino acids and are sources of fat and minerals, but they are less sustainable and can vary significantly in nutrient composition and quality. On the other hand, plant proteins are less variable in their nutrient composition, are a source of vitamins, minerals and dietary fibre, and are a more environmentally-friendly option (Boye et al., 2010).

Although cats are obligate carnivores and require animal-sourced proteins in their diet, complementary plant proteins can be used to provide dogs with all the essential amino acids they require. Read more on our blog about vegan diets for dogs.

Myth #3: Supplemental amino acids are indicative of a low-quality animal protein

Most ingredients, including many animal-based protein sources, are deficient in at least one essential amino acid. Therefore, to ensure amino acid requirements are met, amino acid supplementation is often necessary. The presence of supplemental amino acids in a food is not indicative of the quality of ingredients included the diets, but rather that the amino acid content of the diet has been balanced to ensure it meets the animal’s requirements.

Myth #4: Whole body protein homeostasis (a set of processes that affect the level and stability of protein) is better supported by whole ingredient amino acids rather than synthetic amino acids

The advantage of using individual synthetic amino acids in dog and cat foods is they can help balance the essential nutrient content of the diet to meet the needs of dogs and cats without providing protein in excess. Furthermore, studies have shown that protein peptides composed of synthetic N-methylamino acids in particular have increased stability and increased resistance to protein degrading enzymes (Aurelio et al., 2004).

Myth #5: Omega 3 fatty acids are too unstable to be added to shelf-stable food, and fish oil will quickly oxidize when the bag is opened

Research has shown that although fish oil can undergo oxidation if not properly handled and stabilized, both artificial and natural antioxidant systems (such as mixed tocopherols, a form of vitamin E) can be effective at stabilizing fish oil to prevent premature oxidation (Aldrich, 2006).

Myth #6: Since there is only one hormone to lower blood sugar (insulin), animals are not designed to eat high carbohydrate diets

Maintaining blood glucose levels within a narrow range is critical for animal well-being. While high blood glucose levels are undesirable (diabetes), low blood glucose can result in a hypoglycemic crisis, which can result in death in extreme situations. The body has sophisticated systems in place to maintain blood glucose within the normal range. The number of hormones involved in lowering blood sugar is not indicative of the body’s ability to metabolize carbohydrates. Carbohydrates are an ideal energy source and spare protein to be used for other critical functions.

Healthy animals can handle dietary carbohydrates and evidence does not suggest that a high carbohydrate diet causes diabetes.

Petcurean TeamA Team of Dedicated Pet Parents + Nutrition Experts

In fact, glucose levels remain controlled in healthy animals, regardless of the carbohydrate level and source (Asaro et al., 2018; deOliveira et al., 2008).

Myth #7: Cats dislike sweet tastes, cannot deal with post-feeding glucose surges, and have a limited ability to use starches

Research has shown that cats lack the sweet taste receptor so cannot taste sweetness at all; they are neither attracted nor opposed to the taste (Li et al.,2006). Multiple studies have also observed that cats have a prolonged and flat glycemic response and do not commonly experience post-feeding glucose surges (Asaro et al., 2018). Scientific evidence demonstrates that both dogs and cats can readily digest and metabolize carbohydrates, with no negative impact on the digestion and absorption of other macronutrients (Asaro et al., 2018; deOliveira et al., 2008).

Myth #8: Additional supplementation is essential in a processed kibble diet

By providing a kibble diet that is complete and balanced according to AAFCO, the food contains all the necessary ingredients required to provide optimal nutrition to an animal. Therefore, additional supplementation is not necessary and should be done with caution.

Myth #9: Calcium supplementation is recommended for puppies

Not only is this incorrect, but supplementing puppies with calcium can be very dangerous. Excess calcium supplementation while the animal is still growing can lead to skeletal malformations (Goedegebuure & Hazewinkel, 1986). Over-supplementation of calcium is especially concerning for large and giant breed puppies. To address this, AAFCO has recently implemented a maximum allowable amount of calcium in foods for large breed puppies of 1.8% on a dry matter basis (DMB) (AAFCO, 2018). The minimum calcium requirement for puppies is 1.2% DMB, so the optimal calcium range for large breed puppies is relatively narrow and must be carefully controlled to ensure healthy bone growth and development.

Myth #10: Senior dogs should eat diets with at least 30% protein

There is currently no distinction made in protein requirements for senior dogs compared to adult dogs; senior dogs fall under the category of adult maintenance according to the AAFCO nutrient profiles. High protein diets may not be ideal, or even suitable, for all dogs. When protein is consumed in excess of the body’s requirements, it is broken down into nitrogen-containing compounds and filtered out as waste in the urine. Healthy dogs can handle extra protein, but dogs with renal insufficiency, which is more common amongst older dogs, may benefit from a lower protein diet. Many of the clinical signs of late stage renal insufficiency, such as vomiting and lack of appetite, result from of a build-up of these nitrogenous end products. Feeding a diet that is restricted in protein allows the kidneys to work less and prevents an accumulation of these waste products. However, high quality protein ingredients that provide all essential amino acids in the amount pets require is recommended to help reduce the quantity of waste that the kidneys must eliminate.

Myth #11: Pet food is not safe because it does not require FDA approval before going to market

Pet food, like human food, does not need approval by the FDA before going to market, though it is the ethical responsibility of food producers to ensure only approved ingredients are used and safety measures are met. Regulatory agencies review and test foods on the market to make sure they comply with their labels and do not contain contaminants. However, all food is susceptible to a recall if a regulatory body determines that it poses a hazard to human or animal health. Hundreds of human food recalls occur in North America every year, compared with only a handful of pet food recalls. It is in everyone’s best interest to keep the food supply as safe as possible for ourselves and our pets. Though mistakes can happen, nutrition and food science technologies developed over the past several decades have created a safe food supply to feed millions of humans and their pets.

Myth #12: Extrusion sometimes can’t get rid of all anti-nutritional factors in plant-based ingredients

The presence of anti-nutritional factors is often raised in relation to plant-based ingredients in pet foods. For example, some people are concerned about lectins (a type of carbohydrate-binding protein) in peas. Lectins are believed to have evolved to protect the plant by causing intestinal discomfort in animals that eat them. However, lectins must be consumed raw in large quantities to produce this discomfort, and moderate heat treatment, such as that used to make dry and canned pet foods, inactivates the anti-nutritional properties of lectins (Roy et al., 2010).

In fact, controlled amounts of anti-nutritional factors may have health-promoting properties. Data in humans suggests that when properly processed, lectins may help to prevent or treat certain diseases such as heart disease and diabetes by helping to control obesity (Roy et al., 2010). Preliminary research has shown that lectins also may have anti-cancer and immune-boosting effects (Roy et al., 2010).

Myth #13: Synthetic vitamins are dangerous and do not provide the same benefits as whole foods

The word ‘synthetic’ does not automatically mean that something is inferior. Vitamin manufacturers have developed sophisticated technologies to produce the most useful and stable forms of individual vitamins, which are well utilized and handled by the body.

Many factors are taken into consideration when designing a vitamin or mineral premix, including the nutrient quality, bioavailability, stability, and physical characteristics. Whether it is a vitamin, mineral, or other nutritional supplement, strict quality control is put in place to ensure consistency and safety. Furthermore, since many nutrients react with other food components, adequate stabilization protects the nutrient from degradation and is critical to ensuring correct nutrient levels in the food. There is no research to support defining synthetic vitamins as dangerous when fed in appropriate levels for dogs and cats. Any nutrient can be harmful if fed in excessive levels, whether the source is from foods or supplements. Read more about vitamin supplementation in pet food.

Myth #14: Kibble is not very digestible

A lot of research has been performed to examine the digestibility of kibble and it is in fact highly digestible. Research has demonstrated that the protein, fat and starch digestibility in kibble is upwards of 90% in cats and dogs (Asaro et al., 2017; Sá et al., 2013). Fibre, by definition, is not digested, playing a critical role in digestive health and promoting regularity. Fibre can be particularly important for small breed dogs susceptible to anal glad issues by helping create a bulkier stool.

Myth #15: Processed foods have a higher risk of mycotoxin contamination

The risk of mycotoxin contamination is not related to the processing of pet food; rather, it is related to quality control practices for ingredient sourcing. Testing for mycotoxins in ingredients is a key step in producing healthy and safe food for both pets and humans.

Myth #16: Processed foods negatively affect the microbiome

Many aspects of food and an animal’s overall diet composition affect the microbiome, including nutrient content, prebiotic/probiotic content, and processing methods. Although food processing will impact the microbiome, research in this area is still relatively new and it is unknown whether processing has negative effects.

While processed foods in the human food industry are often viewed unfavourably because many of them are high in fat, salt, and sugar, this is not the case for most pet foods.

Petcurean TeamA Team of Dedicated Pet Parents + Nutrition Experts

There are many advantages to processing food. Processing technologies have evolved significantly over the years to create safe, convenient, nutrient-dense foods, and help secure a stable supply.

Processing can increase the digestibility of some macronutrients, allowing them to be more readily absorbed (Tran et al., 2008). Cooking food is a key step in maintaining food safety by destroying harmful pathogens; undercooked meat is a well-known source of pathogens for both humans and animals. Additionally, processing allows manufacturers to incorporate fibre into kibble, which can subsequently act as a food source for the beneficial bacteria in the GI tract, thereby promoting a beneficial microbiome for the animal.

Myth #17: Carbohydrates in the diet cause a disruption of the microbiome, and impaired nutrient absorption

Studies have shown that consumption of a diet high in carbohydrates can increase the evenness (the balance of bacteria type) of gut microbiota in dogs (Li et al., 2017). A lack of dietary carbohydrates results in intestinal bacteria using amino acids as their energy source, leading to an increased production of ammonia, a foul-smelling compound excreted in the urine. Additionally, we are not aware of any research that supports a negative correlation between carbohydrate content and nutrient assimilation in cats or dogs.

Carbohydrates, namely starch and dietary fibre, are important components of pet foods. Although carbohydrates are often considered ‘fillers’, they do play a critical role in your pet’s body. In particular, carbohydrates provide a highly digestible, readily available energy source. Foods rich in complex carbohydrates are also an important source of essential nutrients.

Fat and carbohydrate are the preferred energy sources for the body, but protein can also be broken down to provide energy. However, animals are unable to store excess amino acids. What is not utilized for tissue maintenance must be dealt with by the liver and kidneys. When compared to carbohydrates and fats, protein as an energy source is metabolically expensive due to the structure of amino acids. The body must first break protein down into amino acids to be utilized for energy. If the amino acids are not needed by the body for another purpose, the nitrogen portion of the amino acids is converted in the liver to an end-product called urea which is excreted in urine, and the carbon portion of the amino acid is converted to fat.

Nitrogen, from urea and other sources, is an environmental contaminant. Overfeeding protein by reducing carbohydrates not only serves as an inefficient use of energy but also leads to increased nitrogen (i.e. urea) excretion and environmental ammonia levels. The more protein that is fed above requirements, the more urea is excreted. High concentrations of urea in the urine result in yellow and burnt spots in grass.

Myth #18: If you feed your puppy less food, they might not get enough calcium

AAFCO minimum calcium recommendations for puppies have been established based on years of research. Switching to a food with higher calcium can be detrimental to puppies and lead to skeletal diseases, especially in large breed puppies.

It is important to continuously monitor your puppy’s weight and body condition score to ensure they are not gaining excess body fat, a sign of overfeeding. Extra calories can increase the rate of growth in puppies which is associated with abnormal bone development.

Myth #19: Food should not be frozen as it can increase oxidation and add moisture to food

Freezing is a centuries-old method of food preservation to prevent microorganism growth. It is one of the safest methods of preservation; without it, tremendous amounts of food would be wasted. Cold temperature storage helps keep food fresher for longer and keeps food safe by decreasing the water activity and reducing the multiplication, resistance, and survival of potentially harmful organisms (Leistner, 1992). Appropriate packaging prevents the gain or loss of moisture. Moisture loss, or ice crystals evaporating from the surface of a product, can occur during frozen food storage which causes freezer burn and a loss in product quality. However, this is easily prevented with proper packaging.

Fat oxidation is what contributes to food going rancid. Fresh meats and fish spoil quickly at room temperature due to bacterial growth. This can be slowed using refrigeration, but the shelf life only extends by a few days. On the other hand, freezing greatly extends the length of time a food can be stored. While fat oxidation and a decrease in omega-3 fatty acid content can occur in frozen foods that have been stored for many weeks, there are significant benefits to freezing for maintaining food safety and quality of fresh meats and fish. Freezing at lower temperatures and rapidly freezing food helps to reduce fat oxidation. Since many people and their pets do not live next to an ocean or lake where fresh fish is abundant, freezing helps increase accessibility to these types of nutritious foods.

Myth #20: Because tests don’t distinguish between pathogenic and non-pathogenic Salmonella, many of the raw foods that are recalled may not pose a risk for illness

There are two species of Salmonella and over 2500 serotypes, or strains. All 2500 serotypes can cause disease in humans; therefore, no strain can be considered non-pathogenic (WHO, 2018). The decision to recall a food is not done lightly; a pet food company would not recall a food unless they were concerned about its safety for the public. Furthermore, the FDA guidance documents for testing for Salmonella span both Human foods, and “Direct-Human-Contact” animal foods, including pet food. Therefore, the same validation processes that apply to human food also apply to pet food.

Myth #21: The pet food industry in North America is largely self regulated

The pet food industry is regulated by multiple bodies including the United States Food and Drug Administration (FDA), United Stated Department of Agriculture (USDA), Association of American Feed Control Officials (AAFCO), and the European Pet Food Industry (FEDIAF). The Canadian Food Inspection Agency (CFIA), the Competition Bureau of Industry Canada and Health Canada are the government agencies involved in the regulation of pet food sold in Canada and abroad.

There are, in fact, multiple government agencies monitoring the safety of pet food, making it a highly regulated industry in North America and throughout the world.

Petcurean TeamA Team of Dedicated Pet Parents + Nutrition Experts

Myth #22: AAFCO focuses on the bare nutritional minimum because it doesn’t set maximums for every nutrient

AAFCO recommendations were developed according to scientific research published by the National Research Council (NRC). AAFCO recommendations typically exceed NRC requirements. Therefore, when a food meets AAFCO minimums, in actuality it often exceeds animals’ nutrient requirements as supported by years of scientific research by the NRC (NRC, 2006). Maximum values for nutrients are established when there is a health risk associated with consuming too much of the nutrient.

The optimal intake range varies from nutrient to nutrient, with some nutrients having a very wide range and others a very narrow range. Without understanding ingredient interactions and the unique attributes of a specific animal, it is very difficult to determine what the optimal nutrient intake is for an individual pet.

Myth #23: Unless you calculate dry matter percentages on a bag, you cannot tell if a food meets AAFCO minimums

All pet foods that meet AAFCO nutrient requirements will carry a nutritional adequacy statement, for example “This food is complete and balanced according to the AAFCO nutrient profiles for Adult Maintenance/Growth/All Life Stages of dogs.” You can look for this nutritional adequacy statement on pet food labels to determine if a food is complete and balanced without the need to calculate dry matter percentages.

Myth #24: If chicken is first on the ingredient panel, it may not actually be the first ingredient due to the inclusion of water

Ingredients on a package are required to be listed in descending order by weight (AAFCO, 2018). This means that if chicken is the first ingredient, chicken is included in the recipe in the highest quantity according to weight. This rule is the same for pet food and human food. Fresh meats naturally contain a high percentage of water and this water contributes to the total weight of the meat. Fresh meats in pet foods provide an excellent source of high-quality protein and enhance the flavour of the food.

Myth #25: Recipe descriptors (i.e. large breed, senior, etc.) have no nutritional requirements and are simply a ploy to charge more money for a product

The AAFCO dog and cat nutrient profiles are divided into two categories – growth & reproduction and adult maintenance. There are not specific nutrient profiles published for different body sizes, breeds, or life stages. However, it is well established that various characteristics of an animal can affect their nutrient requirements. Large breed dogs are a good example. AAFCO has set upper limits for calcium that are specific to large breed puppies to promote healthy bone development (AAFCO, 2018). Another example is that senior diets are often formulated to have reduced calories and fat compared to adult maintenance diets, to support senior pets’ slowed metabolism and help prevent weight gain. Thus, while there are no published regulations for what certain diet ‘descriptors’ mean, they do provide nutritional benefits specific to pets in those categories and are not simply a ploy to charge more money for a product.

Myth #26: Carbohydrates may not be included on the label because pet food companies do not want to report the carbohydrate content of their food

There are only four nutrients that AAFCO requires on a pet food label – moisture, crude protein, crude fat and crude fibre (AAFCO, 2018). AAFCO does not permit labelling of carbohydrate levels; however, it does permit labelling dietary starch and sugars in the Guaranteed Analysis, which are types of carbohydrates. AAFCO does not allow a claim of “low carbohydrates,” “low dietary starch,” or “low sugars.” Furthermore, AAFCO has specific rules about making comparison claims for carbohydrate, dietary starch or sugars (i.e. the amount present in one food compared to that in another food). Since there is often a lack of space on packaging for all the required information, pet food companies must be selective about which information to include. Since carbohydrates are not listed by AAFCO as an essential nutrient, even though the body has a physiological requirement for glucose, carbohydrate is often excluded from the label. However, reputable companies will provide full nutrient information, including carbohydrates, on their website or if contacted directly.

Myth #27: To avoid feeding oxidized foods, it is recommended to feed much earlier than the best-before date

The best-before dates for pet food are not set arbitrarily. Shelf-life stability tests are conducted and peroxide values (which indicate when a food has become rancid) are measured to determine the shelf-life of a food. This testing ensures that the food is stable from the date of manufacture until the best-before date.

Myth #28: A dry dog food should contain no more than 30% carbohydrate, and a wet dog food should contain no more than 7.5%. A dry cat food should contain no more than 15% carbohydrate, and a wet cat food should contain no more than 1.5%

Currently, there is no scientific research that identifies an optimal level of carbohydrates for cats or dogs. There is no evidence to substantiate a “30/7.5%” or “15/1.5% rule”. There is, however, research to support the fact that both cats and dogs can readily digest and metabolize carbohydrates, even at high levels (Asaro et al., 2018; deOliveira et al., 2008). Carbohydrates provide a highly digestible, readily available energy source.

During digestion, carbohydrates are broken down into glucose, the preferred energy source for certain body cells, including the brain. In addition, the consumption of carbohydrates allows protein to be spared for producing and maintaining body tissue, rather than being used for energy production. In humans, some digestion of carbohydrates begins in the mouth. Dogs do not have this oral enzyme, so carbohydrates are only broken down in the small intestine.

Dietary fibre is a unique type of carbohydrate that cannot be digested by a dog’s enzymes. However, it has many benefits. Fibre can help with weight management, improve digestive health and aid in the control of blood glucose levels.

Myth #29: Veterinary diets use low quality ingredients and the biggest difference is the price

Animals do not need ingredients, they need nutrients. This is especially important for pets with certain diseases that can be improved through dietary modification. Veterinary diets may contain ingredients that are the same as ingredients in non-therapeutic diets, but the recipes are different to create diets with specific nutrient levels to treat a particular disease state. Veterinary diets often do not meet AAFCO nutrient profiles and therefore must undergo clinical testing to ensure their safety and efficacy. Substituting for a commercial diet that has similar ingredients is not a suitable option for treating animals with disease.

Myth #30: Supplemented vitamins and minerals on the ingredient list make the quality of the food questionable

Vitamin and mineral supplementation is used in pet foods to balance the nutrient composition and to ensure the healthiest pet foods possible. These supplements act like a ‘nutrition insurance policy’ to provide essential nutrients in the correct ratios required by dogs and cats. While our goal is to use nutrient-rich ingredients to minimize the need for supplementation, nutrition and food science tells us that optimal nutrition cannot always be achieved by natural food sources alone, making supplementation of pet food necessary.

This blog was originally published on May 14, 2019. Last revised July 2021.