Cats are nature's classic carnivores, and although the vegetarian lifestyle is alright for your human family members, serving vegetarian or vegan cat food is not a good choice for your feline friend.
Considered "obligate carnivores," cats are genetically "obligated" to hunt other animals for their nutrition. Human vegans and vegetarians can balance a diet of veggies and live healthily, but this isn't always the case with cats. If you are feeding your cat a vegetarian or vegan dish—or just considering it—take a look at the following and be sure to consult with your veterinarian on your cat's specific needs.
Given the Choice...
Domesticated cats' ancestors were desert-dwelling predators, whose diets consisted of lizards, snakes, birds, rodents, and even some protein-containing insects. Even today's most domesticated house cats are often very skilled hunters—if they want to be.
When they do hunt their food, they eat the whole thing. The majority of this "catch" is digested for the energy a cat needs every day, whereas the rest is regurgitated in the hairball-style fashion you may know all to well. This is important because although your cat's "natural" eating habits don't come into play as often as they do for her wild relatives, they're the best way to keep her healthy unless your vet recommends otherwise. In other words, most cats do not seek out things like grains and vegetables because they aren't what their bodies are built to survive on.
Veggie and Healthy?
A cat is a very resourceful creature. In the event that her normal meat-based food supply isn't available, she can (and will) adjust to a plant food source if it is the only available meal. However, this green diet ultimately doesn't provide the proper amino acids (building blocks for muscles) and nutrients cats need to live a full and healthy life—even if it's something they'd do in an emergency.
Numerous studies have been done on vegetarian cat diets, and the results are not entirely clear. What is clear is that it's not easy to balance a vegetarian diet. In fact, for a vegetarian cat food to meet the needs of your cat, it will still require synthetic amino acids, so it is not possible to have a true natural vegetarian cat food and meet your cat's needs. Beyond this difficulty, it can lead to serious health problems down the line. For example, not having good nutrition has been known to worsen preexisting conditions such as heart disease, urinary tract disease, diarrhea, and more according to PetMD. It has also been linked to heart and eye disease without prior conditions being reported. Your pet's health is not worth the potential risk.