Can cats be vegetarian?

Cornell's Feline Health Center puts it in one line: cats are obligate carnivores, which means they rely on nutrients found only in animal products. This is not a taste preference. It is how their bodies work.

The Merck Veterinary Manual lists the gaps. Cats have a dietary requirement for taurine, an amino acid, and plant proteins are devoid of it, so a cat must have animal protein or added synthetic taurine. Cats cannot turn beta-carotene from carrots or mango into vitamin A, because they lack the gut enzyme to split it, so they need vitamin A already formed, as in liver, fish oil or a synthetic source. They also need arachidonic acid, a fat that is absent in vegetable oils but found in meat, poultry and eggs, and they cannot make enough niacin from other nutrients.

Cats also need more of some amino acids, such as arginine, than dogs do. Merck notes that nutritional problems are most common when cats are fed unbalanced homemade diets, diets made for dogs, or vegetarian diets.

Owner surveys are positive. A 2023 survey in PLOS ONE of 1,369 cats, 127 of them fed vegan food for at least a year, found that the vegan-fed cats tended to have fewer reported health problems, though none of the differences in the seven general measures was statistically significant. A 2021 survey of cats in Canada and the US in BMC Veterinary Research found that owners of cats on plant-based diets did not report worse health, and its authors say the study relies on what owners report, is open to bias, and needs a prospective study to confirm it.

Lab analyses and clinical reports are not. A 2020 PLOS ONE study tested every vegan pet food then on sale in Brazil, including one cat food, and found every food short of at least one nutrient. The cat food was low in potassium and arginine, and could fall short of protein and taurine for cats with low energy needs. A 2021 case report from the University of Toulouse described two cats with anaemia, weight loss and muscle wasting after switching to a plant-based food.

Put together: a commercial vegan food is very different from a home vegetarian diet, because it can add synthetic taurine and vitamin A. But quality varies, the best evidence for safety is owner reporting, and the cost of getting it wrong falls on the cat. If you want to try one, do it only with your vet, who can check your cat's health and blood over time.

Call your vet before changing your cat's diet in any big way, including to a vegan food. Book a visit if a cat that has been on home vegetarian food is tired, eating less, losing weight or muscle, bumping into things or breathing fast. Merck links taurine deficiency to heart muscle disease and retinal damage, and the Toulouse cases began with lethargy and poor appetite. These need a vet, not a diet tweak at home.