Are cats fed a vegan diet healthier than meat-fed moggies? The evidence is still unclear

Are cats fed a vegan diet healthier than meat-fed moggies? The evidence is still unclear
  • PublishedSeptember 17, 2023

Cats fed vegan diets tended to be healthier than their meat-fed counterparts, according to a new study.

But, experts warn, the evidence for benefits in vegan kitties is not that clear-cut.

Despite growing in popularity — the vegan cat food market is now worth an estimated US$9.3 billion — there have been no large, randomised controlled trials to show if purely plant-based diets are, indeed, good for your fluffy friend.

So what has research into vegan cats so far shown? And what do you need to know about vegan cat food?

First, it’s worth taking a look at our furry friends’ nutritional needs.

Not all carnivores are created equal

The carnivore clan is divided into different types.

Cats need nutrients which are provided from eating whole prey animals — they’re what’s known as obligate carnivores.

Dogs, on the other hand, venture into omnivore territory. They’ve evolved ways to digest and extract nutrients from plants. They have a longer small intestine for their body size than cats, and can secrete enzymes that help break down carbohydrates.

Dogs can also synthesise vitamin A from beta-carotene — the pigment that gives carrots their orange hue.

A brown dog with carrot in its mouth
Carrots can be a healthy snack for your pooch too.(Getty Images: Fenne)

And while cats in the wild do eat plant matter from the stomach contents of their prey, their digestive hardware and metabolic machinery has evolved for a mostly meaty diet.

(This is why you shouldn’t feed dog food to a cat, and also means Garfield’s predilection for lasagne might have caused him a bit of … digestive unrest.)

For instance, cats can’t convert beta-carotene to vitamin A, so they must get pre-formed vitamin A from their food.

It’s the same with other essential compounds such as taurine, says Sarah Zito, a veterinarian and RSPCA senior scientific officer for companion animals.

“Those are things that form the basis of concern around feeding plant-based diets to cats.

“That’s not to say that you can’t necessarily get a plant-based diet that could, at least on paper, meet those nutritional requirements.

“But one of the problems we have is a lack of high-quality evidence base for using these diets in cats and their outcomes.”

Research into vegan cat diets so far

One reason for the rise in vegan pet food is the fact that feeding our doggies and moggies comes at an environmental cost.

A 2017 study calculated the production of meat-based cat- and dog food releases the equivalent of 45 to 70 million tonnes of carbon dioxide each year, and that’s just in the US.

Some studies into vegan diets and cat health — including the new study published in the journal PLOS One — do suggest benefits to plant-based foods, such as fewer vet visits and less medication.

But once you scratch the surface and take a look at how those studies were conducted, the findings start looking less solid.

Alex Whittaker, who specialises in animal welfare and law at the University of Adelaide, co-authored a review of the research conducted on vegan diets for cats and dogs.

She says that despite the topic getting recent attention, “there have not been any big, controlled studies that study only the impact of vegan diets”.

“Some were almost like case studies, with only a few cats.”

The biggest studies, like the new PLOS One study, tend to be survey-based. They ask owners to report, for instance, how healthy their pet is.

But without following up with a vet, those kinds of questions are subjective, Dr Whittaker says.

She adds there’s also the risk of unconscious biases creeping in, especially when the people taking the survey are not representative of the wider population.

Of the almost 1,400 people surveyed in the new study, for instance, a quarter said they were vegan, far higher than the 2 per cent reported in the UK, where most of the respondents live.

“That has the potential to bias your responses, because if you believe that a vegan diet is more healthy, potentially your answers to the questions will shine a glowing light on these diets, even though you might not realise you’re doing it,” Dr Whittaker says.

Some studies only asked if cats were fed a vegan diet, not how long they’d been on it. Other studies followed cats on a vegan diet for weeks or a few months — perhaps not long enough for some diet-related conditions to develop.

Plus a cat fed vegan food may not really be vegan, especially if it’s allowed outside. Even indoor cats might find a fleshy snack in the form of mice or geckos.

Ideally, Dr Whittaker says, a study would compare vegan cats with meat-fed cats and control for all these things: keep them in a location where they can’t supplement their meals with prey, track their health with regular vet visits, and do it long enough to get a good idea of the long-term effects of a vegan diet.

What if you’re really keen to start a vegan diet?

The RSCPA’s Dr Zito says if you have a cat, and are keen on trying them on vegan food, think carefully and familiarise yourself with the potential risks.

“It is important for people to realise that there are potential consequences for feeding an unbalanced and inadequate diet to cats which can be quite, quite severe.”

And that’s not just for vegan diets — even meat-based diets can be deficient in various nutrients.

So Dr Zito recommends caution.

Keep a close eye on your cat for health or behavioural changes, and schedule regular follow-up exams and tests to monitor their health.

Before making the switch, check in with your kitty’s vet.

“So that would mean getting a baseline physical examination, blood tests and urine tests,” Dr Zito says.

“If people still wanted to go ahead, it would be a good idea for them to use a commercial food that has been developed by a qualified veterinary nutritionist, and formulated considering the nutritional needs of the cat.”

Specifically, look for food that complies with the Australian Standard (AS 5812-2017) for the Manufacturing and Marketing of Pet Food — this means it includes the required nutrients — and find a formulation that suits your cat, Dr Zito says.

“A kitten needs a different diet from an adult cat who needs a different diet from a geriatric cat, and a geriatric cat with renal disease needs a different diet again.”


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