Common Myths About Pet Nutrition, Corrected

The domestic dog has co-evolved alongside humans for thousands of years and shows genetic adaptations for starch digestion not found in wolves. The notion that grains are inherently harmful to dogs lacks scientific support. More significantly, the FDA began investigating a possible association between grain-free diets — particularly those high in legumes and potatoes — and DCM, a serious heart condition, following a cluster of reports in breeds not typically predisposed to the disease. The investigation is ongoing, but the concern is taken seriously by veterinary cardiologists. Grain-free formulas are not automatically dangerous, but they should not be chosen based on the assumption that they are inherently more natural or nutritious.

Raw diets — particularly those involving uncooked meat, bones, and organs — can harbor pathogens including Salmonella, Listeria, and E. coli. These pose health risks to pets and, critically, to the people handling the food, particularly children, elderly individuals, and immunocompromised household members. Multiple veterinary and public health organizations, including the American Veterinary Medical Association (AVMA), have published position statements cautioning against raw diets for these reasons. Additionally, home-assembled raw diets are frequently nutritionally incomplete without careful formulation by a board-certified veterinary nutritionist. For a thorough comparison of the evidence, see our article on raw diets vs. commercially prepared pet food.

The term "by-product" sounds off-putting, but in the context of pet food regulation, it refers to animal parts other than skeletal muscle meat — including liver, kidneys, spleen, lungs, and tripe. Many of these are richer in specific vitamins and minerals than muscle meat alone. Liver, for instance, is an excellent source of vitamin A, B vitamins, and iron. The regulatory definition specifically excludes hair, hooves, horns, teeth, and similar materials from the by-product category used in feed. Whether a by-product ingredient is high or low quality depends on its source and processing — not simply the word itself appearing on a label. For help interpreting what label terms actually mean, see our guide on reading pet food labels.

Ingredient lists follow a pre-processing weight order. Fresh chicken, for example, may be listed first because it weighs a great deal before cooking — but once moisture is removed during processing, it may contribute proportionally less protein than a lower-listed ingredient like chicken meal, which is already a concentrated dry protein source. This is not inherently deceptive, but it means that reading ingredient order alone is an incomplete way to assess nutritional content. The guaranteed analysis panel — which lists minimum protein and fat percentages and maximum moisture and fiber — provides more actionable nutritional information than ingredient rank.

Cats lack certain metabolic pathways that dogs and humans use to synthesize essential nutrients. They cannot produce adequate taurine (an amino acid critical for heart and eye health), arachidonic acid (a fatty acid), or preformed vitamin A from plant precursors — all of which must come directly from animal-sourced ingredients in their diet. Dog food is not formulated to meet these feline-specific requirements and should never be used as a sustained replacement for cat food. Long-term feeding of dog food to cats can result in serious, preventable nutritional deficiencies. The format differences between wet and dry food also interact with feline hydration needs — explored in our article on wet food vs. dry food for cats and dogs.