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Cat food
Cat food is formulated to address the specific nutritional requirements of cats. Although cats are obligate carnivores, most commercial cat food contains both animal and plant material, supplemented with vitamins, minerals and other nutrients. An important nutrient is the amino acid derivative taurine, as cats cannot synthesize the compound. Cats fed a taurine-deficient dog food may develop retinal degeneration and go blind, for example.[1]
Commercial cat food

Some manufacturers sell frozen raw diets and premix products to cater to owners who feed raw.
Major brand-name dry cat food manufacturers often use primarily grain-based ingredients like corn and rice with meat by-products or animal digest making up the meat ingredients. Some manufacturers offer 'premium', 'natural' or 'holistic' formulas that are by-product free and contains less or no grains. Cats have no metabolic need for carbohydrates as the feline system prefers to create glucose from protein.[2]
Dry food
Dry food is generally made by extrusion cooking under high heat and pressure. Dry cat food has an advantage over wet in convenience and price - besides usually being significantly cheaper, dry cat food can also be left out for the cat to eat at will over the course of several days; whereas, canned or raw cat food spoils or becomes unappetizing after several hours. Using a free feeding practice can also contribute to overeating, and ultimately obesity.[3]
Dry food is recommended by some based on the idea that cats break apart dry foods with their teeth, which causes the food to scrape off dental calculus. Many dry foods use meals as protein source, such as meat meal, chicken meal, fish meal, or corn gluten meal.[citation needed] This allows manufacturers to produce cheaper foods. Since the occurrence of BSE infection through contaminated meat and bone meal, the use of meat meal in pet foods has been prohibited in parts of the world (e.g. USA).[citation needed] Comparative studies conducted by Japanese researchers have shown that meat meal is superior to the other protein meal sources in terms of dry-matter digestibility and nutritional value for cats, while corn gluten meal is the least nutritional.[5][6][7]
The same studies showed that cats fed with these dry food diets excreted alkaline urine. Urine pH has been implicated in the formation of struvite crystals in feline urolithiasis, and many dry food manufacturers address this by adding urine-acidifying ingredients to their food.
Wet food
Canned or wet food generally comes in common can sizes of 3 oz (85 g), 5.5 oz (156 g), and 13 oz (369 g). Owners and veterinarians who recommend a diet consisting largely or entirely of canned, homemade or raw cat food point to higher water content of such food and the increased total water consumption in comparison to a dry food diet as an important health benefit. Wet food also generally contains significantly less grain and other carbohydrate material. Many foods are made with fish however and excessive consumption of fish (which contains high levels of unsaturated fatty acids) can cause yellow fat disease.[9]citation needed]

Canned cat foods in pop-top containers may play a role in the development of hyperthyroidism in cats[13].
Vegetarian or vegan food
Vegetarian or vegan cat food has been available for many years, and is targeted primarily at vegan and vegetarian pet owners. [15] Cats are obligate carnivores and require nutrients (including arginine, taurine, arachidonic acid, vitamin A, vitamin B12 and niacin) found in meat sources that cannot be obtained in sufficient amount in plant sources. According to the National Research Council, "unsupplemented vegetarian diets can result in harmful deficiencies of certain essential amino acids, fatty acids, and vitamins." [16] Vegetarian pet food companies attempt to correct these deficiencies by supplementing their products with synthetically produced nutrients.
Organizations that advocate vegan or vegetarian diets for people have split opinions regarding vegetarian or vegan cat food. The International Vegetarian Union[17], the Vegan Society[18] and Peta[19] are some of the organizations that support a vegan or vegetarian diet for cats. On the other hand, the Vegetarian Society suggests people "consider carefully" and that many cats will not adjust to a vegetarian diet. [21] The animal welfare organization American Society for the Prevention of Cruelty to Animals, although suggesting a supplemented vegetarian diet for dogs,[22] recommends against a vegetarian and vegan diets for cats.[23]
One study evaluated cats whose owners were knowledgeable about vegetarian cat diets and had self-selected to feed commercial and/or homemade vegetarian diets.[15]The study found that all the cats had serum cobalamin levels within the reference range but 3 of 17 cats had serum taurine values below the reference range. While low blood taurine level is indicative of long-term deficiency, the values were described as "marginal, but... While there are anecdotal reports linking a vegetarian diet with urinary tract problems, no documented case report or study exist.[15][24] A survey done during the above study showed that a quarter of respondents perceive feline lower urinary tract disease as a health risk of feeding a vegetarian diet.[15]
A few vegetarian cat food brands are labeled by their manufacturers as meeting AAFCO's Cat Food Nutrient Profile while other manufacturers recommend their products to be supplemented and not used as a standalone. A 2004 study evaluated two commercial pet foods for nutritional adequacy;Vegecat KibbleMix supplement and Evolution canned diet for adult cats. The study concluded that these two foods, counter to labeling claims, had multiple nutritional inadequacies when compared against the AAFCO minimal nutrient profile for cat diets. The authors recommended that these vegan diets should not be used as a sole source of nutrition for cats.[25]
In response, Evolution Diet denied that their product is nutritionally inadequate, citing the "ten to twenty thousand healthy and long living dogs, cats and ferrets living on the Evolution Diet" as an example.
Labeling
In the United States, cat foods labeled as "complete and balanced" must meet standards established by the Association of American Feed Control Officials (AAFCO) either by meeting a nutrient profile or by passing a feeding trial. Cat Food Nutrient Profiles were established in 1992 and updated in 1995 by the AAFCO's Feline Nutrition Expert Subcommittee. The updated profiles replaced the previous recommendations set by the National Research Council(NRC).
Certain manufacturers label their products with terms such as premium, ultra premium, natural and holistic. Such terms currently have no legal definitions.
Nutrients and functions
Vitamins are organic compounds that take part in a wide range of metabolic activities. Twelve minerals are known to be essential nutrients for cats. Calcium and phosphorus are crucial to strong bones and teeth. Cats need other minerals, such as magnesium, potassium, and sodium, for nerve impulse transmission, muscle contraction, and cell signaling. The table below lists the AAFCO nutritional profiles for cat foods along with the roles of vitamins and minerals in cat nutrition according to the National Research Council.