Can cats thrive on a plant-based diet?

Note: This paper was written by my friend Aashish Bharadwaj, and published here with permission.

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 ingredients 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, 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.

Can cats 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. “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 shows 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.

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.

But what about these studies showing some vegan cat foods to be incomplete in Brazil and Germany?

What about the ‘Mineral analysis of complete dog and cat foods in the UK and compliance with European guidelines’ study 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 the Brazil study 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, and Evolution).

The full text of the German study 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 the UK study.

That being said, all major brands of nutritionally complete plant-based cat foods say they comply 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.

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.” Multiple reviewed studies showed positive health outcome data.

Polymyopathy? Anemia?

• 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

Two studies (‘Vegan versus meat-based cat food: Guardian-reported health outcomes in 1,369 cats, after controlling for feline demographic factors’ and ‘A cross-sectional study of owner-reported health in Canadian and American cats fed meat- and plant-based diets’) 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 the first study but were present nonetheless.

Food analysis

‘The Nutritional Soundness of Meat-Based and Plant-Based Pet Foods’ study 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, including some who have done so for more than 10 years. One purports to have fed their cat plant-based for 13 years before they passed away at the age of 20, which is well above the average cat lifespan.

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 is 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 actually animal abuse, especially considering the data showing that this is wholly unnecessary.