The Misconceptions Cat Owners Still Believe About Feline Nutrition

Kittens produce lactase, the enzyme needed to digest their mother's milk. As cats mature, lactase production typically drops significantly — meaning cow's milk (which contains more lactose than cat's milk) is poorly digested by most adult cats. The result is often diarrhea, gas, or vomiting. Cream is worse: higher fat content adds calories without nutritional value. If you want to give your cat a liquid treat, plain water is always the right choice. "Cat milk" products with reduced lactose exist but should be treats, not dietary staples.

Cats are often fixated on tuna's strong smell and flavor, but that preference doesn't reflect nutritional suitability. Canned tuna for humans lacks added taurine, is high in unsaturated fats, and when fed exclusively, can cause yellow fat disease (steatitis) — a painful inflammatory condition caused by vitamin E deficiency. Long-term feeding also raises concerns about mercury accumulation. Tuna as an occasional treat in small amounts is generally considered low-risk, but it should never form the base of a cat's diet. Nutritionally complete commercial cat foods are formulated to avoid these gaps.

The appeal of raw feeding is understandable — cats evolved eating prey, not processed kibble. But the argument from nature overlooks real hazards. Raw meat can harbor Salmonella, Listeria, and E. coli, posing risks not just to the cat but to people in the household, especially children and immunocompromised individuals. Parasites like Toxoplasma gondii are also a concern. Beyond contamination, homemade raw diets are frequently nutritionally incomplete. Both the American Veterinary Medical Association and the American Animal Hospital Association have issued policy statements advising against raw protein diets for these reasons. If you're considering raw feeding, a board-certified veterinary nutritionist can help evaluate the risks for your cat's specific situation.

The low-protein-for-seniors guideline was based on older research and has since been substantially revised. Aging cats are actually prone to muscle wasting (sarcopenia) and often have reduced ability to digest and utilize protein efficiently. For healthy older cats, adequate high-quality protein supports muscle mass and immune function. Protein restriction is specifically indicated for cats with confirmed chronic kidney disease (CKD), where managing phosphorus and reducing nitrogenous waste matters — but applying that restriction to healthy seniors can accelerate the very muscle loss it's meant to prevent. Your veterinarian should guide dietary adjustments based on bloodwork and health status, not age alone.

"Grain-free" became a powerful marketing label, but it conflates two separate questions: whether grains are harmful (they generally aren't, in modest amounts in a complete diet) and whether a food is nutritionally balanced. Many grain-free formulas substitute grains with legumes like peas or lentils, which can be harder for cats to digest and have been investigated in connection with diet-related dilated cardiomyopathy (DCM) in dogs — though the feline picture is less clear. What matters is whether the food meets AAFCO nutritional standards for your cat's life stage, not whether it carries a trending label. See how food format choices affect your cat in our guide to wet and dry food nutritional differences.