NO, You Can't Feed Your Cat a Vegan Diet

Posted on 11 Apr 2017 03:47 by EricT


In June of 2014 the image of an article started circulating on Facebook. The headline read '"Vegan" Kitten Nearly Dies." Is it true? Did a kitten nearly die from being fed a vegan diet?

Yes, this report was a real one. It was an article that had been published in Australia's Herald Sun on July 22, 2013

The kitten in the report had been fed a diet of potatoes, rice milk, and pasta. The owners, according to the veterinarian who treated the cat, were believed to be vegan.

The kitten, extremely weak and on the verge of death, was suffering from malnutrition. Obviously, cats need different nutrition than humans, but many are unaware of just how different those needs are. Not only can cats not survive on a vegan diet, they cannot even do well on a vegetarian diet.


You know that cats, whether domestic or wild, are carnivores, and carnivores need a lot of protein. But cats are unusual. They are not just any old carnivore, they are hypercarnivores. They are sometimes called obligate carnivores. This term means what it sounds like: Cats are obligated to eat meat. They don't get to choose not to based on ideological reasons and if you choose this for your cat, you will likely shorten its life.

You see, most carnivores, despite a preponderance of meat in their diet, are actually somewhat omnivorous. Dogs, as you know, can and will eat all sorts of foods, and they can make use of the nutrients in these foods. They have the machinery, if you will, necessary for many different biomechanical pathways for converting nutrients from both animal and plant sources into energy and specific nutrients that they can use. A primary difference between the cat and the dog's nutritional requirements is that cats need much more protein than dogs in their diet.

Protein Requirements for Cats versus Dogs

In fact, cats require their diets to have a higher percentage of protein than almost any other mammal. You may be surprised to learn that dogs only require around 4% of their food (based on the dry weight) to be comprised of protein. Growing puppies, of course, need more, around 12 percent.

Cats, although estimates vary, need up to 12% protein at a minimum, and kittens need up to 18%. This makes cats unusual among carnivores.

Why Do Cats Have Such a High Protein Need?

As mentioned above, dogs have the ability to use other types of food besides meat and convert the nutrients into usable energy and other substances required for basic body maintenance. A dog, for example, can use the protein they get pretty much exclusively for maintaining muscle and other body structures, and for many other biochemical pathways. They don't necessarily need to get their energy from protein. They can derive energy from carbohydrates or fats, therefore preserving protein for these needs. We humans are much the same. When a dog's diet is low in protein, the dog's body will simply avoid using the protein for energy and use it for other essential body maintenance.

Cats require protein both for maintaining their bodies and for deriving energy. In the cat's liver, protein undergoes gluconeogenesis, which converts the protein into glucose for energy, via enzymes that break down protein. Whereas humans and dogs can start and stop this process, only using protein in this way when it is needed, cats cannot shut down the protein-converting machinery in their liver. Therefore, protein has to play double-duty. It is needed for the maintenance and growth of the body's tissues, for basic metabolic functions, and for basic energy. If a cat is fed a low protein diet, the cat's body will not step down the conversion of protein into energy, meaning that the cat will not be able to maintain its body within normal parameters.

Amino Acid Requirements

All mammals, regardless of the amount of crude protein in their diet, need the right amino acids. Amino acids are the building blocks of proteins, and individually, they can have important roles in the body. There are 11 essential amino acids for cats: arginine, histidine, lysine, leucine, isoleucine, valine, methionine, threonine, tryptophan, and asparagine. This is similar to any mammal, but the cat has a higher need for some of these. For those who want to feed their cat homemade cat food, it is important to be aware of these amino acid needs.

Cats have a very high need for dietary taurine. Commercial cats foods are supplemented with taurine for this reason. Humans and dogs can biosynthesize taurine from cysteine but the enzyme that is needed for this conversion is not very active in cats.

A cat fed a high meat diet could still be deficient in taurine, since it is not contained in the same proportion in all meats, and it is not a component of proteins. Taurine is actually a ß amino acid or sulfonic acid and its bioavailability can differ depending on the ingredients in a cat's food. For example, chicken by-product meal, typically used for commercial cat foods, contains some taurine, but this taurine seems to be completely unavailable, so supplemental sources of taurine are added to make up for this shortfall. Before this change, cats fed commercial diets often died of heart failure. A diet without adequate taurine can cause cardiomyopathy, retinal degradation, and reproductive problems.

Cats also need arginine in large amounts. Even a temporary surfeit of arginine in the diet can have dramatic results in a cat. Protein contains a lot of nitrogen. In order for this nitrogen to be excreted it must enter the urea cycle. Arginine is an essential precursor for this cycle. If sufficient arginine is not present in a cat's diet, excess nitrogen will build up as ammonia in the cat's blood, which is toxic.

Cats also have a high need for sulfur-containing amino acids like cysteine and methionine.

Vitamin A

Vitamin A is another example. Humans, as well as most carnivores, can use vitamin-a precursors called carotenoids, found in fruits and vegetables, and convert them into vitamin A. These are yellow and orange pigments like those found in carrots, for example, which contain beta-carotene. Cats do not have the ability to use these compounds to make vitamin A. They must, therefore, obtain vitamin A from animal sources.

You do not have to worry about your cat getting vitamin c from fruits or vegetables, however, because cats can make their own vitamin C.


Cats also use fats for energy, essential fatty acids, and certain biological functions. They can tolerate a high level of fat in their diet, and they can even use the fats found in plants, which are typically called oils. However, cats still must have animal fats in their diets as this is the only source of arachidonic acid. We humans, like most omnivores, can convert linoleic acids from plants into arachidonic acid. Cats do not have enough of the enzymes required to do this. Arachidonic acid is required to make prostoglandins and other compounds needed for reproduction.


Today, there are a great many sources claiming that the cat food industry is poisoning your cat, and that you should feed your cat a homemade diet. In fact, many people feeding their cats homemade diets are not giving their cats all of the nutrients they need. Although not all cat food is created equally, it does have all the nutrients your cats need to be healthy, including the proper amount of protein. Of course, it may also contain elements your cat does not need. For example, your cat does not need carbohydrates, whether from corn meal, rice, or potatoes. However, they can digest and utilize starches and most sugars (don't give your cat table sugar they are not very good at dealing with it), very well, and use these carbohydrates for energy. However, they are not as good at clearing excess glucose after a high carbohydrate meal, so the amount of carbohydrate in their diet needs to be controlled.

Although with very careful manipulation, a number of supplements, a hope and a prayer, it may be possible to feed your cat a vegan diet and have it remain healthy, you will probably spend more time planning it than you do your own diet. It is, quite frankly, irresponsible to take the chance based on your own ideologies. Cats are carnivores and we have no right to force our dietary choices on them.

1. Bradshaw, John W. S., Rachel A. Casey, and Sarah L. Brown. The Behaviour of the Domestic Cat. Wallingford: CABI, 2013.
2. Laflamme, Dottie, and Debra L. Zoran. Clinical Nutrition. Philadelphia, PA: Elsevier, 2014
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