Cat Nutrition Myths That Persist Despite the Evidence

The image of a cat lapping milk from a saucer is deeply embedded in cultural memory, but it doesn't reflect feline physiology. After weaning, most cats produce significantly less lactase — the enzyme needed to digest lactose — making cow's milk difficult to process. Even small amounts can trigger gastrointestinal distress. If you want to offer a liquid treat, plain water or cat-specific lactose-free milk products are better-tolerated options.

Cats evolved as desert hunters whose primary water source was their prey — which is approximately 70% moisture. Dry kibble typically contains only 8–10% moisture. Research in feline hydration consistently shows that cats fed exclusively dry food consume meaningfully less total water than those eating wet food, even when fresh water is freely available. Chronic mild dehydration is associated with increased risk of urinary tract issues and kidney disease in cats. This doesn't mean dry food is always inappropriate, but relying on it as a cat's sole hydration strategy carries real risk.

The grain-free trend in pet food was largely driven by human dietary preferences projected onto pets. While cats have limited ability to digest large amounts of carbohydrates, grains in commercial cat food are typically present in modest amounts and are generally digestible once cooked. The more important concern is the overall macronutrient profile — particularly adequate animal protein — not whether grains appear on the ingredient list. Many grain-free formulas substitute grains with potatoes or legumes, which may still be high in carbohydrates. Always evaluate a food by its complete nutritional analysis rather than a single marketing claim.

While cats are often drawn to fish by its strong smell, a diet composed almost entirely of tuna or other fish carries significant risks. Raw fish contains an enzyme called thiaminase that destroys thiamine (vitamin B1), potentially leading to neurological problems. Feeding large amounts of certain fish also risks mercury accumulation over time. Additionally, fish-heavy diets can lack adequate levels of vitamin E, potentially causing a painful inflammatory condition called steatitis. Fish can be a component of a balanced diet, but it should not be the foundation of every meal.

Free-choice feeding — leaving food out at all times — works for some cats, but it's not a reliable strategy for most. Indoor cats with limited activity levels are especially prone to consuming more calories than they expend. Feline obesity is associated with diabetes, joint problems, and a shortened lifespan. Portion-controlled meals based on your cat's weight, age, and activity level are generally a more reliable approach. Your veterinarian can help determine an appropriate daily caloric target for your specific cat.