Can Cats Be Vegetarian or Vegan?

The question comes up more often now than it used to. Owners who eat vegan or vegetarian diets ask, reasonably, whether their cat could do the same. The internet has loud answers in both directions. The actual evidence is calmer than either, and it is also more one-sided than the dog version of this question.

For dogs, the conversation has shifted. The British Veterinary Association updated its position in 2024 to acknowledge that a carefully formulated plant-based diet for a dog is nutritionally possible. Dogs are facultative carnivores, closer to omnivores in practice. The same body maintained its position on cats: they remain obligate carnivores, and the essential nutrients they need from animal tissue cannot be reliably replaced by plant ingredients.

That is the short version. The longer version is about which nutrients, and why supplementation does not fully close the gap.

What an obligate carnivore actually needs

We have written about feline obligate carnivory in Why Your Cat Cannot Just Eat Anything. The shorthand for this post is that millions of years of evolution on whole prey left cats with a set of nutritional requirements that other species do not share.

Several of these requirements come from nutrients that are either absent from plant tissue, present in forms cats cannot use, or required in amounts plant tissue cannot reasonably deliver.

Taurine is the cardinal example. It is an amino acid found in animal tissue, particularly heart and other muscle. Cats cannot synthesise it in adequate amounts. The discovery that taurine deficiency causes dilated cardiomyopathy in cats, published in 1987, changed commercial cat food formulation permanently. Plants do not contain taurine.

Preformed vitamin A is the second. Dogs and humans can convert beta-carotene from plants into retinol, the active form of vitamin A. Cats lack the enzyme to do this efficiently. They need retinol itself, which is found in animal tissue, particularly liver.

Arachidonic acid is the third. It is a long-chain fatty acid present in animal tissue. Most mammals can synthesise it from linoleic acid, which is present in plants. Cats have very limited ability to do this conversion and need preformed arachidonic acid in the diet.

Vitamin B12, niacin, and the sulphur amino acids methionine and cysteine round out the list. Cats need them in amounts and forms that plant ingredients do not naturally supply. Arginine is a separate problem: cats have an unusually high requirement and an unusually low tolerance for deficiency, with serious symptoms developing within hours of a deficient meal.

The synthetic supplementation question

The reasonable next question is whether all of this can be supplemented synthetically. Taurine is manufactured synthetically. Retinol is manufactured synthetically. So are B12, arachidonic acid, and the amino acids. In principle, a plant-based diet plus a full synthetic supplement package could meet the nutrient targets on paper.

Three issues sit between principle and practice.

The first is bioavailability. A nutrient on a label is not always a nutrient the cat absorbs. Bioavailability of a synthetic compound in a plant matrix can differ from absorption of the same nutrient in animal tissue, and the long-term studies needed to confirm equivalence in cats are limited.

The second is urinary chemistry. Cats fed plant-based diets tend to produce more alkaline urine, which raises the risk of struvite crystals and urinary tract problems. This is a known and reproducible effect of dietary change in cats.

The third is the gap between formulation and finished product. Independent analyses of commercial vegan cat foods, starting with Gray and colleagues in 2004 and continued by Kanakubo and colleagues in 2015, have repeatedly found nutrient levels below AAFCO targets, including for taurine, arachidonic acid, and vitamin A. Those shortfalls turned up in the products actually tested, in study after study.

What the pro-vegan studies actually say

The case for plant-based cat diets in the recent literature comes mostly from a small group of researchers, with the Dodd group at the University of Guelph and the Knight group at the University of Winchester (with Australian co-authorship at Griffith and Murdoch Universities) producing most of the published work.

The 2021 Dodd study and the 2023 Knight survey both reported that owners feeding plant-based diets did not perceive their cats to be in worse health than owners feeding meat-based diets. The Knight study examined seven general health indicators in 1,369 cats and found a directional pattern favouring the vegan group, but the differences were not statistically significant. Both studies relied on owner-reported health, by survey, with no clinical measurement, no blood work, no longitudinal follow-up, and self-selected respondents who were almost all vegan themselves.

The Knight study disclosed funding by ProVeg International, a plant-based food advocacy organisation. That is the same kind of disclosure that matters when industry funds research on the other side, and is worth naming for the same reason.

The studies establish that some cats appear to tolerate these diets in the short term according to their owners. They do not establish nutritional safety in the way that, for example, an AAFCO feeding trial does. A 2024 opinion piece in Frontiers in Veterinary Science by Knight and colleagues argued the broader case for vegan pet diets, but it is an opinion piece, not new clinical evidence.

The veterinary nutrition mainstream remains where it was: the long-term clinical evidence base for vegan cat diets is thin, the products available have a track record of nutritional inadequacy, and the established cat-specific risks are well documented. The BVA position reflects that.

What this means in practice

This is not a moral argument. Owners who choose plant-based diets for themselves usually do so for thoughtful reasons, and the impulse to extend that to a pet is understandable. The evidence on cats specifically is what makes this different from the dog version of the question. A dog has metabolic flexibility a cat does not.

If you want to reduce the environmental footprint of your cat's diet, the options worth looking at are mainstream ones: choosing foods with sustainably sourced fish or poultry, reducing food waste, or feeding the correct amount rather than overfeeding. A truly carnivore-suitable plant-based cat food, validated by long-term feeding trials and clinical follow-up, does not yet exist on the Australian market.

Related reading

• Why Your Cat Cannot Just Eat Anything The peer-reviewed research on feline obligate carnivory and macronutrient regulation.
• By-products and “Meat Meal”: What They Actually Are Why organ meat matters nutritionally and what the label does and does not tell you.
• Grain-Free Cat Food: What the Evidence Says Why the FDA grain-free investigation was a dog story and what the cat evidence actually shows.

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