Cat Nutrition Fundamentals

Unlike dogs, cats are obligate carnivores, meaning their bodies are specifically adapted to require nutrients found in animal tissue and cannot thrive on a vegetarian or vegan diet. Cats need preformed vitamin A (they cannot efficiently convert plant-based beta-carotene), arachidonic acid, and taurine, an amino acid found only in animal tissue that is essential for heart and eye health.

Taurine deficiency in cats can cause serious, sometimes irreversible problems including dilated cardiomyopathy (a heart condition) and retinal degeneration leading to blindness. Reputable commercial cat foods are formulated to include adequate taurine and other essential nutrients; homemade diets require careful, veterinary-nutritionist-guided formulation to avoid dangerous gaps.

Look for food labelled as 'complete' rather than 'complementary' (sometimes called 'treat' or 'snack' food), as complete foods are formulated to meet all of a cat's nutritional needs on their own, while complementary foods are meant to be combined with other foods. Feeding only complementary food as a sole diet can lead to nutritional deficiencies over time.

Reputable brands generally follow recognised nutritional guidelines (such as those from FEDIAF in Europe or AAFCO in the US) and will state this compliance on the packaging. This provides a reasonable baseline assurance of nutritional adequacy, though individual cats may still do better on some formulations than others.

Both wet and dry complete foods can meet a cat's nutritional needs, but they differ meaningfully in moisture content: wet food is typically around 70-80% water, while dry food is much lower, around 6-10%. Because cats evolved from desert-dwelling ancestors and have a relatively low thirst drive, cats fed primarily dry food may take in less total water than those eating wet food, which is relevant for urinary tract health.

Many vets recommend feeding at least some wet food, or a mixed diet of wet and dry, particularly for cats with a history of urinary issues, though individual preferences, dental considerations and lifestyle also factor into the best choice for a specific cat.

Cats naturally eat multiple small meals throughout the day rather than one or two large meals, reflecting their evolutionary history as hunters of small prey. Splitting daily food into several smaller portions, or using puzzle feeders to encourage natural foraging behaviour, can suit many cats better than one or two large meals, and may help reduce obesity risk by discouraging rapid overeating.

Measuring food according to packaging guidelines (adjusted for the individual cat's weight, age, activity level and any health conditions) rather than free-feeding ad libitum helps prevent the gradual weight gain that is common in indoor cats with lower activity levels.

Fresh, clean water should always be available, changed regularly, and placed away from food and litter trays, as some cats are reluctant to drink near these areas. Some cats strongly prefer moving water and may drink more from a pet water fountain, which can be a useful tool for cats prone to urinary issues or those on a primarily dry diet.

Signs of inadequate hydration can include lethargy and reduced skin elasticity, though changes in drinking or urination habits can also signal underlying illness such as kidney disease or diabetes, and should prompt a veterinary visit rather than assumptions about diet alone.

Some common human foods are toxic to cats, including onions, garlic, chocolate, grapes and raisins, and xylitol. Cow's milk is not a necessary or recommended part of a cat's diet, since many adult cats are lactose intolerant and can develop digestive upset from dairy despite enjoying the taste.

Significant diet changes should be made gradually over a week or more by mixing old and new food in increasing proportions, as abrupt changes can cause digestive upset. Any sudden loss of appetite in a cat, especially an overweight cat, warrants prompt veterinary attention, as cats can develop a serious liver condition (hepatic lipidosis) if they stop eating for even a few days.