Can Cats Thrive on a Plant-Based Diet?

A review of the conventional wisdom, data, and individual cases

Introduction

Feeding cats a plant-based diet can certainly raise controversy, to say the least. Many will claim this practice is animal abuse while failing to recognize that the animals killed for the cats’ food were also abused and subsequently slaughtered.

Aren't cats obligate carnivores?

Cats are obligate carnivores. People assume this to mean that cats need meat, but that is not what an obligate carnivore is. An obligate carnivore is defined as an animal that needs specific nutrients only naturally found in animal flesh. In the case of cats, these nutrients include taurine and preformed Vitamin A (retinol), among others.

Cats need nutrients, not ingredients. The source of these nutrients is not of consequence, and the data discussed later confirms this. Most taurine in meat-based cat foods is actually added synthetically due to the proteins being denatured during processing. This same synthetic taurine is also added to commercial plant-based cat foods and is chemically identical to naturally occurring taurine in animal flesh.

Is it natural?

This is an appeal to nature fallacy. Cats also do not naturally eat cooked sheep, cattle, swine, or chickens pumped full of antibiotics, yet these are found in traditional commercial cat food. Medication is not natural either (but FIV is), yet most people wouldn’t argue against veterinary care. Cats are opportunistic carnivores who hunt small animals to survive, but inside our homes, they are far removed from that environment and rely on us for nutrition and stimulation. What matters is health outcome data, not whether something is “natural”.

But cats can't digest carbohydrates!

Commercially available plant-based cat food isn’t high in carbs. But also, this is a false statement. Evidence shows that not only are carbs not harmful to cats as some believe, but that they have no issues digesting them [8]. “Cats have considerable metabolic flexibility and carbohydrates can provide a protein-sparing effect, meaning that less protein is required for gluconeogenesis when dietary carbohydrates are provided. So long as dietary protein needs are met, cats are able to adapt well to either high-fat or high-carbohydrate diets.”

Why are you forcing them to be vegan?

Cats are not and cannot be vegan, as veganism is an ethical position that cats do not have the agency to adopt. However, health outcome data show that cats can survive and thrive on a plant-based diet.

Regardless of what you feed your cat, they are being “forced” to eat that food, whether it is plant-based or animal-based. So if vegans are “forcing” their cats to “follow their philosophy”, then meat eaters are “forcing their cats to follow their philosophy” as well. The truth is that cats tend to be picky and won’t eat something they don’t want to, but they are not being forced to do anything when they willingly eat the food we place in front of them.

If your cat had a chance, wouldn't they hunt birds?

And? I’m sure they’d also avoid going to the vet if they could. Children would choose to eat candy for lunch if they had the chance.

And, barring a debate between indoor and outdoor cats, they don’t have the autonomy to do what they want. They live where we want, poop in the boxes we give them, and eat what we feed them.

My vet/An online article says that cats need meat.

This is known as an appeal to authority fallacy. “Experts” are frequently wrong on things, and vets aren’t nutritionists. Additionally, expert opinion is the lowest on the hierarchy of evidence.

I can find an “expert” saying anything, and there are experts promoting plant-based cat foods. In fact, the co-author of several of the studies cited below, Dr. Sarah Dodd, has a PhD in veterinary nutrition and states that a plant-based diet for cats is safe and healthful.

But what about this study showing some vegan cat foods to be incomplete in Brazil and Germany [5] [6]?

What about this study [7] showing that only 38% of dry meat-based cat foods and only 6% of wet meat-based cat foods are nutritionally complete and fully adhere to regulatory guidelines? In addition, fish-based foods were found to have high levels of heavy metals.

These papers don’t reveal the brands they studied, but [5] lists the ingredients. Only one was cat food (the rest were dog food), and that food was purchased at a local Brazilian store and isn’t any of the mainstream commercial brands (Amicat, Benevo, Nature’s HUG, Wild Earth, and Evolution).

The full text of study [6] is not available. It is unclear whether the FEDIAF and AAFCO guidelines directly correlate to long-term health. Either way, this “problem” is certainly not unique to plant-based cat foods, as seen in [7].

That being said, all major brands of nutritionally complete plant-based cat foods claim to comply (just like all meat-based cat foods) with agencies regulating cat nutrition. Benevo is FEDIAF compliant, Nature’s HUG and Evolution both exceed AAFCO standards, and Amicat is compliant with both FEDIAF and AAFCO. You can always check specific compliance on a manufacturer’s website.

The data

The data is clear: Cats can survive and thrive on a plant-based diet in the long term. See below.

Systematic review

A systematic review, looking at 49 studies, concluded that “there is no convincing evidence of major impacts of vegan diets on dog or cat health.” [1]

Multiple studies were analyzed and showed positive health outcome data.

The study mentioned polymyopathy and anemia!

Congratulations, you briefly skimmed the systematic review without fully understanding it or diving deeper.

The nature of a systematic review is that all literature on the topic is reviewed. One study (29 in the reference list of the systematic review) is an experimental study from 1992 where some cats were fed an experimental human vegetarian diet, some with potassium supplementation, and some without. The purpose of that experiment was to study the effect of potassium supplementation. You can see the full paper here: https://sustainablepetfood.info/wp-content/uploads/2023/02/Veg-feline-diets-Leon-et-al-1992.pdf

The other study (30 in the reference list of the systematic review) was a case study of two cats presenting to the emergency room with anemia who happened to be fed a plant-based diet.

The systematic review itself states that these are low-quality studies.

Guardian outcome data

Studies [2] and [3] use guardian-reported health outcome data. While this is not as robust as clinical data, it’s the best data we have, and both show positive health outcomes. The positive health outcomes were not statistically significant in [2] but were present nonetheless, and the review mentions that these results are consistent across independent studies and should therefore not be disregarded. In fact, “no statistically significant difference” is a great result and demonstrates that plant-based diets are not harmful.

Food analysis

Study [4] analyzed the nutritional content of various commercial cat foods, both plant-based and meat-based, and most “had acceptable or superior standards at nearly all stages examined, throughout the design, manufacturing, transportation, and storage phases, with plant-based diets slightly superior to meat-based diets overall.”

Anecdotes

Here is a small subset of people who have fed their cats plant-based food, including some who have done so for more than 10 years.

Conclusion

Cats can survive and thrive on a plant-based diet. There is no evidence to suggest any negative health outcomes as a result of feeding cats commercial-grade plant-based kibble on a long-term basis. Arguments made against a plant-based diet for cats tend to be founded on conventional wisdom and logical fallacies without any supporting evidence that the source of nutrients affects cat health.

It isn’t animal abuse (quite the opposite, in fact), and paying for innocent individuals to be selectively bred to be unnaturally large, mutilated without anesthetic, confined in tiny cages, raped and forcibly impregnated, and then loaded onto a truck that takes an arduous journey to a slaughterhouse where they will scream and thrash in a gas chamber or be shot in the head or hung upside down and electrocuted is actual animal abuse, especially considering the data showing that this is wholly unnecessary.

References

[1] Domínguez-Oliva, A., Mota-Rojas, D., Semendric, I., & Whittaker, A. L. (2023). The Impact of Vegan Diets on Indicators of Health in Dogs and Cats: A Systematic Review. Veterinary Sciences, 10(1), 52. https://doi.org/10.3390/vetsci10010052

[2] Knight A, Bauer A, Brown H (2023) Vegan versus meat-based cat food: Guardian-reported health outcomes in 1,369 cats, after controlling for feline demographic factors. PLoS ONE 18(9): e0284132. https://doi.org/10.1371/journal.pone.0284132

[3] Dodd, S.A.S., Dewey, C., Khosa, D. et al. A cross-sectional study of owner-reported health in Canadian and American cats fed meat- and plant-based diets. BMC Vet Res 17, 53 (2021). https://doi.org/10.1186/s12917-021-02754-8

[4] Andrew Knight, Natalie Light. (2021). The Nutritional Soundness of Meat-Based and Plant-Based Pet Foods. Revista Electronica De Veterinaria, 01 - 21. Retrieved from https://www.veterinaria.org/index.php/REDVET/article/view/92

[5] Zafalon RVA, Risolia LW, Vendramini THA, Ayres Rodrigues RB, Pedrinelli V, Teixeira FA, Rentas MF, Perini MP, Alvarenga IC, Brunetto MA. Nutritional inadequacies in commercial vegan foods for dogs and cats. PLoS One. 2020 Jan 17;15(1):e0227046. doi: 10.1371/journal.pone.0227046. PMID: 31951617; PMCID: PMC6968870.

[6] Starzonek J, von Lindeiner L, Vervuert I. Beurteilung in Deutschland erhältlicher veganer Alleinfuttermittel für Hunde und Katzen [Assessment of vegan complete diets for dogs and cats available in Germany]. Tierarztl Prax Ausg K Kleintiere Heimtiere. 2021 Aug;49(4):262-271. German. doi: 10.1055/a-1552-2220. Epub 2021 Aug 23. PMID: 34425604.

[7] Davies, M., Alborough, R., Jones, L. et al. Mineral analysis of complete dog and cat foods in the UK and compliance with European guidelines. Sci Rep 7, 17107 (2017). https://doi.org/10.1038/s41598-017-17159-7

[8] Laflamme DP, Backus RC, Forrester SD, Hoenig M. Evidence does not support the controversy regarding carbohydrates in feline diets. J Am Vet Med Assoc. 2022 Jan 28;260(5):506-513. doi: 10.2460/javma.21.06.0291. PMID: 35092659.