The Truth Behind Popular Pet Food Myths

The popularity of grain-free diets was largely driven by the idea that grains are "filler" or that pets are biologically unsuited to digest them. In reality, dogs have evolved digestive enzymes that handle starch efficiently, and grains like oats, barley, and brown rice can contribute valuable fiber, vitamins, and minerals. Cats are obligate carnivores and do better with lower carbohydrate loads overall, but the issue is not grains specifically.

Of greater concern: the U.S. Food and Drug Administration (FDA) investigated a potential association between grain-free diets — particularly those high in legumes like peas and lentils — and dilated cardiomyopathy (DCM), a serious heart condition, in dogs. The investigation is ongoing and causation has not been established, but the signal is significant enough that many veterinary cardiologists advise caution. Pets with a diagnosed grain allergy (relatively uncommon) may benefit from grain-free options, but that determination should be made with veterinary guidance.

"By-product" is a regulatory term referring to parts of an animal other than skeletal muscle meat — think liver, kidneys, lungs, and spleen. In human food cultures around the world, these are considered delicacies. In pet food, they can be excellent sources of protein, vitamins (particularly B vitamins), and minerals including iron and zinc.

The concern about quality is more relevant to vague ingredient names like "meat by-products" versus named sources like "chicken by-products." Named sources are more traceable. Overall, by-products are not inherently inferior — they are often more nutrient-dense per gram than plain muscle meat. For more on decoding what ingredient names actually signal, see our pet food label guide.

The appeal of raw feeding is understandable — minimally processed, "species-appropriate" food sounds intuitively right. But multiple veterinary nutrition organizations, including the American Veterinary Medical Association (AVMA), have noted concerns about both nutritional completeness and pathogen risk. Studies have detected Salmonella, Listeria, and other bacteria in commercially prepared raw pet foods, posing risks not just to pets but to the humans handling those foods.

Nutritional imbalances in homemade raw diets are also common. Without formulation by a board-certified veterinary nutritionist, it is difficult to ensure correct calcium-to-phosphorus ratios, adequate taurine (critical for cats), and appropriate vitamin levels. Our article on raw versus commercially prepared pet food explores this debate in full.

Ingredients are listed by pre-cooking weight, which means a fresh chicken listed first may shrink considerably once moisture is removed during processing — ultimately contributing less protein by dry weight than it appears. Manufacturers sometimes use "ingredient splitting," listing different forms of the same ingredient separately (e.g., peas, pea protein, pea flour) to push them lower on the list while collectively they may be a dominant ingredient.

A more reliable approach is to look at the guaranteed analysis — the percentages of crude protein, fat, fiber, and moisture — alongside the AAFCO adequacy statement. The full label reading guide walks through each section of a pet food panel in detail.

Dogs are omnivores and can meet their needs from a wide range of diets. Cats, however, have evolved as strict carnivores and cannot synthesize certain nutrients that other animals produce internally. Taurine (an amino acid essential for heart and eye health), arachidonic acid, and preformed vitamin A are among the nutrients cats must obtain from animal tissue. Feeding a dog food to a cat — or assuming that what works for one species generalizes to the other — can result in serious deficiencies over time.