Vegetarian feline diets

The death and suffering inflicted upon approximately 80 billion chickens, pigs, sheep, cows, and other animals, both intensively and extensively farmed, who are slaughtered annually, and upon similar numbers of intensively farmed or wild-caught fish, in order to fulfil the desire of some human beings for meat, has been thoroughly documented; as have the deleterious environmental impacts of both intensive and extensive animal farming.

It is because of the ethical concerns of a growing population of vegetarian animal guardians, and because of medical conditions such as allergies which are caused by beef, lamb and other meat-based dietary ingredients, that vegetarian pet food brands were first developed. However, feline vegetarian diets remain the subject of considerable controversy, which is exacerbated by ignorance of the health and nutritional issues involved, including among veterinarians and other experienced animal carers.

To assist animal guardians, animal carers and veterinary personnel who wish to gain a sounder understanding of these issues, this page examines the evolutionary adaptations of cats that equipped them for a carnivorous diet in their original environments, and the relevant natural behaviour of cats. It examines the palatability, nutritional and bioavailability requirements of vegetarian feline diets. It provides the results of a population study of the health of vegetarian cats, and describes the health benefits reported in some cats after transitioning to nutritionally sound vegetarian diets. Finally, it explores the need for quality control of vegetarian feline diets.

1.2 Evolutionary adaptations to a carnivorous diet

Dogs may be biologically classified as omnivores, due to their ability to subsist on a mixed diet of animal and plant based material in their natural environments. In contrast, cats are classified as obligate carnivores, because their evolutionary anatomical, physiological and biochemical adaptations to a carnivorous lifestyle prevent them from deriving substantial benefit from the available plant based material in their natural environments. Both wild cats and dogs do consume plant material, primarily sourced from the gastrointestinal tracts of their consumed prey. However, the nutritional limitations of natural environments are not relevant to animals maintained on artificial meat, plant, mineral and/or synthetically based diets – as almost all domesticated cats and dogs are.

1.3 Unnatural behaviour?

Critics sometimes claim vegetarian diets violate cats’ rights to express natural feeding behaviour, and claim that commercial meat-based diets allow greater expression of that behaviour. This claim definitely warrants further scrutiny.

The natural hunting behaviour of cats was directed toward a variety of small mammals, birds, and large insects found in the cat’s environment. Kills resulted in gorging of as much of the carcasses as possible to prevent consumption by competitors. These were followed by periods of hunger of uncertain duration.

The feeding patterns of normal domesticated cats are far removed from natural patterns. Cats fed commercial meat based diets typically receive canned food at regular times once or twice daily, with dry kibble often available ad libitum (always). Commercial meat-based diets contain assorted animal body parts, slaughterhouse wastes, 4-D meat (from dead, dying, disabled or diseased animals), supermarket rejects, styrofoam packaging, rendered dogs and cats from animal shelters, sometimes with detectable levels of euthanising solution; old restaurant grease complete with high concentrations of dangerous free radicals and trans fatty acids; bacterial, protozoal, fungal, viral, and prion contaminants, along with their assorted endotoxins and mycotoxins; hormone and antibiotic residues; and dangerous preservatives (see Meat based-diets).

As veterinarian Dr. David Jagger put it in the Vegepet Gazette, commercial meat-based diets involve:

“1) domesticating cats and preventing them from hunting their own food;
2) killing literally millions of chickens, cattle, sheep, horses, fish, etc., to feed domestic pets. It is hard to see how cats have a right to eat the flesh of animals such as those listed above, when this flesh would never form a part of a feral or wild cat’s diet. Moreover, since this flesh has often been condemned as contaminated or unfit for human consumption, deliberately feeding it to cats threatens their health and is closer to a violation of than a promotion of cats’ rights.”

Fish-based diets are frequently offered, despite their high levels of PCBs, heavy metals and other toxins (see Meat based diets), and despite the fact that fish are not a natural prey animal for cats. As Gillen (2003) aptly puts it, “Try this experiment: skip your cat’s breakfast one morning and bring him or her to the beach instead. Driven by hunger, what natural instincts might kick in? What are the chances that your cat will splash into the water, swim fifty or so miles out into the deep ocean, and there engage a 1200-pound animal (an adult tuna can be as large as a horse) in an underwater battle to the death in order to fulfill the natural feline diet of fish? The idea that fish is a natural food for cats is absurd.”

Saucers of milk are also frequently offered, despite the lactose intolerance of a significant proportion of cats. Other than gulls and petrels, who drink elephant seal milk, and humans, who drink cow and goat milk, the drinking of milk by adults, much less of another species, is virtually unknown in nature, and is certainly unknown to cats. The obvious enjoyment by many cats of cows’ milk, fish, meat-based kibble, canned commercial diets, vegetarian diets and other foodstuffs naturally unavailable to them is no more a reflection of natural feeding behaviour than is a child’s enjoyment of sweets – and, in some cases, no healthier.

In fact, cats prefer commercial cat food brands not because they perceive them as ‘natural,’ but because they have been conditioned by additives such as digest – the industry euphemism for partially digested entrails from chickens and other animals – to enjoy them. According to Small Animal Clinical Nutrition, “Digest is probably the most important factor discovered in recent years for enhancing the palatability of dry food for cats and, to a lesser degree, dogs.” (Lewis et al. 1987). In fact, digest is so effective that long term exposure can result in apparent symptoms of addiction, necessitating considerable patience and persistence when implementing dietary changes.

Companion animal guardians are often also misled by insidious effects of digest. Although digest usually comprises autolysed chicken entrails, some batches are considered to taste more like beef, fish or turkey, etc., than other batches. Sometimes it’s the type of digest added, rather than the meat origin, that determines the flavour designation on the label. Undifferentiated partially dissolved ‘beefy’ tasting entrails might be labeled ‘Beef Stew,’ while the substitution of ‘fishy’ tasting digest may transform a can into ‘Ocean Whitefish.’

Critics of vegetarian cat food on the basis that it is ‘unnatural’ often display a curious inconsistency. They are generally happy to microchip, vaccinate, worm and sterilise their cats, and to provide them with warmth, shelter and a regular food and water supply, all of which are unnatural. As Dick Gregory states in relation to dogs, “It never seems to occur to the pet owner that the dog would prefer to relieve itself on the carpet, and would probably prefer not to roll over and play dead! Pet owners think nothing of housebreaking a dog, or training it to do tricks or to attack unwanted visitors; in short, to do things for the owner’s benefit. But the same owner resists changing a pet’s diet for the pet’s benefit, and training the pet to eat it!” (Peden 1999). The double standards displayed by otherwise caring animal guardians may partially stem from a deep seated personal need to justify the suffering and death underpinning past and present dietary choices for their animals and themselves.

Regardless of whether or not a meat-based commercial diet is natural for cats, raising chickens, pigs, sheep or cows in intensive or extensive conditions of confinement, conducting surgical mutilations without anaesthesia or analgesia (pain killers) during the normal course of husbandry, and then killing them at a young age in the frightening environment of a modern slaughterhouse, is hardly respectful of what is natural for them. These factors are unquestionably of far greater ethical weight than any discomfort a cat might or might not experience in transitioning to a vegetarian diet.

Whatever combination of animal, plant, mineral or synthetically-based ingredients are used, diets should be formulated to meet the palatability, nutritional and bioavailability requirements of the species for which they are intended.

2.1 Ensuring palatability

As stated above, the common fixation of cats in particular to meat-based commercial brands to which they have become accustomed is primarily due to the addition of ‘digest,’ the industry euphemism for partially digested entrails, usually of chickens. Considerable patience and persistence may be required when altering the diets of cats who have been exposed to digest long-term.

Cats vary widely in their dietary flexibility. In order to transition some cats onto a vegetarian diet, it may first be necessary to withhold all food (not water!), for one day. This will stimulate the appetite without harming healthy adults. It is always advisable to change the diet gradually, e.g., by using 90% old and 10% new diet for a few days, then switching to 80% and 20% for a few more days, thereby transitioning to the new diet over several weeks, or even longer if necessary. A gradual change is more acceptable behaviourally, and also allows an appropriate transition of digestive enzymes (to the extent possible) and intestinal flora (bacteria), thereby minimising the chance of gastrointestinal reactions such as diarrhoea.

Cat guardians should demonstrate by their behaviour that they consider the new diet just as edible as the old (without possibly warning or alarming the cat by making a fuss). They should not be concerned if their cat eats around the vegetarian food at first; just having it in close proximity to the other food will help create the necessary mental association. Mixing the food thoroughly may help, as may the addition of odiferous (the sense of smell is very important) and tasty additives, such as nutritional yeast, vegetable oil, nori flakes and spirulina. Gently warming the food may also help. Guardians should remove uneaten food and offer only fresh food.

The most important factors for difficult cats are gradual change and persistence. Using these principles, the most stubborn of cats have been successfully weaned onto healthy vegetarian diets. Vegetarian cat food recipes may be obtained from Peden (1999) and Gillen (2003), and from some suppliers of nutritional supplements.

In Vegetarian Cats & Dogs, Peden (1999) recounts numerous stories of healthy vegetarian cats who have come to love their diets. New Zealander Ann Fullerton states of her Siamese, Melaney, “Despite the fact only vegetarian food is available from us, no cat has ever deserted us for a home where the menu is more to their taste.”

Grayson the tomcat also judged the palatability of vegetarian cat food more than acceptable: “His owners put him outside winter nights because they have a baby. Though we don’t have snow, winters here are still chilly. It didn’t take Grayson long to discover our cat door is left permanently ajar for Ossie’s benefit. And that chairs and laps by the wood burner are warmer than sleeping under our house. But he is too big to easily squeeze through the cat door. Thumps and clatterings from the laundry always signal Grayson is gamely fighting his way in, one massive shoulder at a time — luckily the door is sturdy! The endearing thing about him is the way he loves vegetarian cat food. What are you to do with a cat that literally squeaks with joy at the prospect of ‘Vegecatised’ cat porridge? — then bolts every mouthful, purring loudly? His owners complain Grayson has lost interest in his meat. So I’ve stopped giving him the vegetarian breakfast he politely requests after a night at our place. Instead he’s firmly but regretfully sent home out of fairness to his owners. I’ve also stopped giving him tea. Nothing daunted, he now turns up for a vegetarian morning tea and supper! It does look as if he wants to move in with us, but ethics aside (he does have a good home) we couldn’t afford to care properly for such a big animal. But he’s a very welcome visitor.”

Alfredo Kuba of Mountain View, California, demonstrated the full range of feline fussiness when describing his two male rescued stray cats Mussi and Tommy (Kuba 2004): “My experience is that animals can adapt to a vegan diet well, it is just a matter of being patient and experimenting with combinations of flavors until you find what they like. Mussi loved the food even though it took about 5 or 6 months of experimenting with vegan recipes to get him to gradually adjust to his new diet. I switched him to a vegan diet after he became ill with diabetes at the age of three on commercial pet food. His diabetes greatly regressed and he finally passed away at the age of 17 after 14 healthy years on a vegan diet. We just rescued and adopted another stray cat we named him Tommy. We started him immediately with Evolution vegan food and we didn’t have to get him to adjust to it, he loved the food from the get go!”

2.2 Nutritional content

Certain nutrients are of particular importance to cats maintained on vegetarian diets, as they are scarce in the plant material available in the cat’s natural environment, and are naturally sourced from small mammals, birds and insects. These are listed in the Appendices.

Regardless of the ingredients used, diets should be complete and reasonably balanced with respect to all essential nutrients, or disease is likely to result, sooner or later. This may be achieved by adding a vegetarian nutritional supplement to a home-made diet (recipes are available from some suppliers of supplements), or by feeding a nutritionally complete commercial diet. Ideally this should be certified as meeting the nutritional standards of the Association of American Feed Control Officials (AAFCO), or equivalent national authority. The Committee on Animal Nutrition, reporting to the Board of Agriculture within the US National Research Council (NRC), has developed nutritional standards for at least 15 species. Historically AAFCO used the NRC recommendations, but in 1993 began publishing its own expanded nutrient requirements, which are now widely recognised as the required nutritional standards for animal feeds. In order to meet AAFCO nutritional requirements, manufacturers of vegetarian (and, in some cases, meat-based diets), diets rely upon vegetable, mineral and synthetic sources of nutrients otherwise derived from animal tissues.

2.3 Bioavailability

The bioavailability of nutrients (extent to which they are available to the tissues) is determined largely by their level of digestibility into simple molecules capable of absorption through the intestinal mucosa. The importance of digestibility is increased in animals such as cats and dogs that have relatively short intestinal tracts. Fortunately, several studies have demonstrated ample digestibility of vegetarian dietary ingredients in cats and dogs.

Pencovic and Morris (1975) studied the apparent digestibility of starch (added at 35% of dietary dry matter) found in corn or wheat grain. Apparent starch digestibilities for coarsely ground, finely ground, or coarsely ground and cooked grains were: corn, 79, 94, and 88%; and wheat, 92, 97, and 96%, respectively. It was concluded that starch from corn and wheat, especially when finely ground, is well utilised by the cat (National Research Council 1986, 6).

The digestibility of some sources of protein has been evaluated in the dog. Hegsted and colleagues (1947) found that the apparent digestibility of proteins in an all-vegetable diet containing white bread, corn, rice, potatoes, lettuce, carrots, onions, tomatoes and applesauce was 80.0% (plus or minus 7.7 %). James and McCay (1950) reported that the apparent protein digestibility of commercial, dry-type food, containing both vegetable and animal proteins, ranged from 67 – 82% for adult dogs. Kendall and Holme (1982) reported the apparent crude protein (Nx6.25) digestibility coefficients for textured soy protein, extracted soy meal, full-fat soy flour, and micronised whole soybeans ranged from 71 to 87%. Moore and colleagues (1980) reported apparent digestibility values of soybean meal, corn, rice, and oats by mature Pointers to be in the range of 77 to 88%. Their data revealed that normal cooking procedures did not significantly influence the digestibility of rice, oat, or corn protein. Their data also indicated that increasing the fat content of the diet from 10 to 20% did not alter the digestibility of nitrogen in a corn and soybean-based diet. Burns and colleagues (1982) showed that the apparent digestibilities of lactalbumin, casein, soy protein, and wheat gluten are 87, 85, 78, and 77%, respectively (National Research Council 1986, 12).

Pet food manufacturers are well aware of the acceptable digestibility of plant-based ingredients, which make up a large proportion of the products they sell.

Analysis of 16 studies on the impact of vegan diets on cat and dog health
Domínguez-Oliva et al. (2023) concluded, “there was no overwhelming evidence of adverse effects arising from use of these diets and there was some evidence of benefits. … Much of these data were acquired from guardians via survey-type studies, but these can be subject to selection biases, as well as subjectivity around the outcomes. However, these beneficial findings were relatively consistent across several studies and should, therefore, not be disregarded.” They advised, “… if guardians wish to feed their companion animals vegan diets, a cautious approach should be taken using commercially produced diets which have been formulated considering the nutritional needs of the target species.” [i.e., that are nutritionally-sound].

In 2023 veterinary Professor Andrew Knight and colleagues published a large-scale study of 1,369 cats fed vegan (127 – 9%) or meat-based (1,242 – 91%) pet food, for at least one year. Cats fed vegan diets had better health outcomes for each of seven general health indicators studied. First, differences between diet groups in age, sex, neutering (desexing) status and primary location (outdoor vs. indoor) were all controlled for statistically. Next, risk reductions were calculated for cats of average age, and other characteristics. For average cats fed vegan diets, risk reductions were:

• increased veterinary visits (possibly indicating illness) – 7% reduction
• medication use – 15% reduction
• progression onto a medical diet (after being fed a vegan or meat-based diet) – 55% reduction
• reported veterinary assessment of being unwell – 4% reduction
• reported veterinary assessment of more severe illness – 8% reduction
• pet guardian opinion of more severe illness – 23% reduction.
• Additionally, the number of health disorders per unwell cat decreased by 16%.

No reductions were statistically significant, but collectively they revealed a strong trend. Additionally, the prevalence of 22 of the most common feline health disorders was studied. Forty two percent of cats fed meat, and 37% of those fed vegan diets suffered from at least one health disorder. 15 disorders were most common in cats fed meat, and seven most common in cats fed vegan diets.

In 2021 veterinarians Dr Sarah Dodd and colleagues published a large-scale study, including dietary information for 1,026 cats, of whom 187 were fed vegan diets. The latter were more frequently reported by guardians to be in very good health. They had more ideal body condition scores, and were less likely to suffer from gastrointestinal and hepatic (liver) disorders, than cats fed meat. No health disorders were more likely, for cats fed vegan diets.

And in 2006 veterinarians Dr Lorelei Wakefield and colleagues published a study in the Journal of the American Veterinary Medical Association comparing the health status of 34 cats maintained on vegetarian diets, and 52 maintained on conventional diets, for at least one year. No significant differences existed in age, sex, body condition, housing, or perceived health status between the two groups. Most of the caregivers in both groups described their cats as healthy or generally healthy. 

Additionally, numerous guardians of vegetarian cats have reported their experiences in Peden’s (1999) Vegetarian Cats & Dogs. Such case reports suggest that nutritionally sound vegetarian feline diets may be associated with health benefits such as decreased ectoparasites (fleas, ticks, lice and mites), improved coat condition, allergy control, weight control, decreased arthritis, diabetes regression, and improved overall vitality.

Ectoparasites and coat condition
Carol Arens of Arkansas reported that her cats appeared to have less ectoparasites, after using an oat-soy recipe and Vegecat supplement. She stated, “… the yeast in the recipe appears to repel fleas and ticks so that they are not a problem, in spite of the fact that we live in the country. Furthermore, Rudy appears to truly relish and anxiously anticipate the taste of her meals.” (Peden 1999).

The Wall Street Journal reported the experiences of Mary Currier, of New Hampshire, who provides a sanctuary for 13 cats and three dogs. She stated, “Their fur is so much softer. It is so much shinier. I sound like a commer­cial, but I can’t believe it, I mean that’s how much better off they are. … If only you could just see these animals and feel the texture of their fur. I think you should put that in because it’s very important. Their fur doesn’t fall out like it used to. It’s thicker! It’s summer now, and the cats are in the house. It’s amazing. I can’t say enough about it and I tell everybody. I’m so grateful.” (Hwang 1993).

Particularly touching is the story of Fletcher, recounted by Jennifer Friedman of Oregon: “[We found] Fletcher a year ago on a subway in New York City. He lived in a small crate that was caked with filth. Two homeless boys, barely able to care for themselves, fed him what they could from time to time. When Ben bought Fletcher off of them for 20 dollars, it did not look like he was going to make it. He was obviously severely dehydrated and malnourished. He had great difficulty walking; it seemed that the muscles in his legs had atrophied from living in the crate. His head was enormous for his small, bloated body and his fur was dry and matted. He was infested with fleas, mites, intestinal worms, and ringworm was spreading on various parts of his body. He also had severe behavioral problems, as would be expected, and had a tendency to attack rather viciously when something scared him. He was such a mess it was overwhelming, but I was afraid that a veterinarian would insist on putting him to sleep. So we decided to do our best on our own. Knowing where to begin was the most difficult part. We bathed him, cleaned out his ears, and used various herbs to treat the mites and ringworm (tea tree oil is excellent for getting rid of fungus) (*). We treated him very specially and with great care so as not to frighten him. We warned visitors not to pet him (we lived in a very tiny one bedroom and couldn’t really isolate him), but not many people wanted to visit us; everyone thought we were crazy! Only a few months earlier I had begun the transition to feeding my two other cats a vegetarian diet. So Fletcher was introduced to my cats’ favorite food at the time — ground chickpeas and brown rice mixed with veggies, oil, tamari, Vegecat, and tons of nutritional yeast. I also encouraged him to drink a lot; he especially loved soy milk (it’s still his favorite today), and to eat liquid vitamin E to help his skin heal. Needless to say, he was by far the easiest convert to a vegetarian diet (I’ve converted four other cats to date). He still eats his food with gusto and maintains a perfect body weight. Two months after we took Fletcher off the subway, we were moving to San Francisco. In order to take him on the plane, we had to get him a health certificate. We took him to a holistic veterinarian. Upon examining Fletcher, the vet commented on what a beautiful and healthy cat he was and what a wonderful disposition he had. I laughed as I told him the condition we found him in only two months earlier. The vet was incredulous.” (Peden 1999).
(*) Tea tree (melaleuca) oil may cause toxic signs when applied to, or licked from, the skin of cats and dogs, particularly at inappropriate high doses, and is not recommended (Villar et al. 1994).

Allergy control
Possibly associated with the proliferation of artificial dyes, flavourings, preservatives (especially ethoxyquin), stabilisers and adulterated slaughterhouse products in commercial meat-based pet foods, the prevalence of companion animal allergies is rising. As stated by allergy expert and veterinarian Dr Alfred Plechner, animal products provoke the most allergic reactions, with beef at the top of the list for both cats and dogs. Changing to another commercial meat-based pet food usually does not resolve the problem, because of the similarity in ingredients used (Plechner & Zucker 1986). Consequently several meatless prescription diets have been formulated to address allergies.

Itchiness is the most common sign of a food allergy for companion animals, although vomiting, coughing or wheezing (feline asthma) can also develop. Cats are more prone to food allergies than dogs, and become increasingly sensitive with age. They may develop skin disorders such as feline miliary dermatitis, or eosinophilic granuloma complex.

Canadian Valerie Cline recounted her story of Barney: “I am proud to share my home with five cats, one of which is named Barney. Barney has suffered from allergies since I welcomed him into my home and these allergies are severe. I was told by many vets that he had food allergies, so I tried changing foods, but nothing I found, even the lamb and rice formulas, would work. Cortisone was the miracle ‘cure’ presented to me every time I took him to the vet and without it his entire head would become red, swollen and itchy. Barney would scratch until all of his fur was gone and he drew blood. His ears would fill up with bloody scabs and his eyes would ooze bloody discharge until they became swollen shut and he would begin to wheeze. Barney was prescribed cortisone for two years until he became diabetic. All along I desperately asked many vets for an alternative, namely a diet I could prepare at home, but I was told that cortisone was a common treatment for feline allergies and that he was so severely ill that cortisone was the best route to take. Barney then required insulin injections every day. He went into insulin shock twice until the dosage was regulated. I was told that Barney would be diabetic and insulin dependent for the rest of his life. Only then was it recommended he start a ‘hypoallergenic diet’ recommended by my vet. He was still allergic, but not severely. The food cost me $50 a month and he had to be kept separate from all the other cats because they ate different food and one mouthful of Science Diet and Barney would be in distress without the security of a cortisone injection for a quick fix. Then I found your product and within one month Barney was completely off the insulin and healthier than I had ever seen him. It has now been four months since he started eating Vegecat and he is no longer diabetic. His ears and eyes are clear and he looks fantastic!” (Peden 1999).

Urogenital disease
Canadian Gwyn Watson describes the beneficial effects on ‘Layla’ of a vegetarian diet: “My cat Layla had a chronic bladder infection. She was on medication from the vet three to four times per year for the last four years. When she was not on medication I managed to keep it under some control with liquid vitamin C. Any stressful situation (i.e., moving) caused a flare-up. Since being on Vegecat she has not had any more trouble. I have not even been giving her the vitamin C. We make the Oat-Soy recipe and add chopped up carrots and sprouts. I found that I had hardly any trouble talking them into this new diet, also.” (Peden, 1999).

Weight control and arthritis
Obesity is an important and growing problem for domestic cats. Potentially serious health problems related to obesity include impaired cardiac func­tion and respiratory disorders. As veterinarian Dr. Gregory MacEwen (1989) states, “Obesity can be one of the major conditions which can adversely affect the longevity of a pet.” Vegetarian diets contain decreased protein and fat levels and increased dietary fibre, all of which are effective in promoting a healthier weight.

Obesity also predisposes to arthritis. Veterinarian Dr. Michael Lemmon (1991) also holds free radicals accountable. He states, “Free radicals are formed during normal cellular metabolism, when cells take in nutrients, assimilate and utilize the nutrients, and then excrete the waste products. Some of these waste products are free radicals. Wherever you find poor quality foods being eaten, you will also find an excess of free radicals. Rancid fats and moldy grains are two leading sources of free radical production in animals. … Fat is an essential ingredient in any diet. Many commercial pet food manufac­turers have problems with controlling the rancidity in fats added to the food they pro­duce. They unsuccessfully use chemicals to try to curb this rancidity. American grain is quite often polluted with varying degrees of mold. Pet food manufacturers, for economic reasons, usually use the lower quality grain products in their pet food. Many cases of arthritis will respond effectively and quickly to antioxidant nutrients such as vitamin C, vitamin E, Beta-carotene, and selenium. Another highly effective antioxidant is the enzyme combination of superoxide dismutase (S.O.D.) and catalase.”

Diabetes regression
The excess body weight more commonly encountered on meat-based diets predisposes to obesity, and transitioning to a vegetarian diet can sometimes result in regression of diabetes. Alfredo Kuba (2004) of Mountain View, California, described an amazing regression of diabetes after transitioning his male rescued stray cat Mussi (castrated at 2 months of age) to a vegan diet:

“I have been feeding my cats vegan food for over 14 years. I can tell you that my experience has been to say the least phenomenal. My cat Mussi who passed away last December was 17 years young. My wife and I rescued him only a couple of weeks old, abandoned. Before he became vegan, we used to feed him the ordinary, commercial ‘pet food’ and he became ill with diabetes at just 3 years of age. I then decided to change his diet. I did some research and started him on Vegecat from Harbingers of a New Age. He loved the food even though it took patience to get him to gradually adjust to his new diet, about 5 to 6 months to be exact.

I noticed once he was eating 100% vegan his diabetes started to regress. Mussi was taking 14 units of insulin a day, 7 units twice a day to normalize his blood sugar before he was vegan. After the diet change to vegan, he rapidly reduced his intake need of insulin to only 2 units a day, and some days, and even weeks passed, when he didn’t need the insulin.

Mussi’s Diabetes was diagnosed by my vet and also the regression as well. I also checked his blood sugar once a week and when he showed symptoms of thirst and excessive urination. He started regressing when I started him on the vegan diet and it took about 6 to 8 months to get the insulin dosage from 14 units a day to only 2 units a day. Some times we noticed that he would go onto shock from too much insulin even at 2 units a day so we checked his blood and for weeks or months at a time he didn’t require insulin, although he remained dependant on it once he got diabetes.

This was a dramatic improvement and quiet astonishing. We just rescued and adopted another stray cat we named him Tommy. We started him immediately with Evolution vegan food and we didn’t have to get him to adjust to it, he loved the food from the get go!”

Improved vitality
Peden (1999) suggests the improved vitality seen in some cats after switching to a vegetarian diet may be due to conservation of energy previously used in the production and excretion of animal waste products, such as urea, creatinine, phenols, sulfates, and phosphates, which are much less encountered on a vegetarian diet.

New Zealander Ann Fullerton describes the effect on her Siamese, Melaney: “The good news is the excellent effect Vegecat had on Melaney, our beautiful Siamese. Mel is 10 years old, and was acting her age. But after just two or three weeks of Vegecat supplement, she was literally racing around and behaving as playfully as a kitten. It was wonderful to see her return to her old self. Ossie, our chinchilla, also benefited.…Did I ever tell you Melaney won two first prizes at the local cat show on her vegetarian diet? Alas, her prizes included a complimentary tin of horrible old Jellymeat!” (Peden, 1999).

Kelp-related benefits
Kelp is sometimes used in vegetarian animal diets, sourced from factories in the United States, Nova Scotia, Eire, Scotland, France, Denmark, the Netherlands, Norway, and South Africa. Ascophyllum nodosum is the species most commonly used. The meal derived from kelp is claimed to have a food value equal to that of oats, to prevent or cure mineral deficiency diseases, and to result in “better milk, eggs, meat, and fur” in ‘production’ animals (Thorvin Inc., undated).

Kelp appears beneficial for bone strength. As stated by Zorn (1974) in Seaweed and Vitality, “Studies were made of the blood calcium, phosphorus, iron, and iodine on patients with fractures at different intervals during convalescence. Professor Cavanaugh learned that the healing time of fractures was reduced 20% by giving the patient a daily ration of kelp. Accordingly, it was clearly indicated in the study that kelp raised the level of calcium in the blood.”

Concerns have previously been voiced that vegan cats may experience urinary alkalinisation, predisposing to urolithiasis (urinary stone formation) and lower urinary tract dysfunction (i.e. urination difficulties and blockages). However, neither our 2023 study, nor Dodd et al.’s 2021 study, showed any increased risk of lower urinary tract dysfunction in vegan cats. Dodd et al. included 1,026 cats whose diets were known, of whom 187 (18%) were fed vegan diets. We included 1,369 cats, of whom 127 (9%) were fed vegan diets. The prevalence of lower urinary tract dysfunction was not statistically significantly different between cats fed vegan and meat-based diets, in either study. Hence, this concern appears to have been unfounded.

Two studies have demonstrated nutritional inadequacies in commercially available brands of vegetarian cat or dog food. Kienzle and Engelhard (2001) found that common deficiencies of European vegetarian cat and dog foods included sulfur-containing amino acids, taurine, vitamin D, vitamin B12, arachidonic acid, and trace minerals. Gray and colleagues (2004) found that two American vegetarian cat food brands were deficient in certain amino acids, trace minerals, vitamins, and in arachidonic acid. One was also deficient in overall protein content. These deficiencies occurred contrary to the expectations of the manufacturers, and contrary to the nutritional information supplied on the labels. Such deficiencies clearly demonstrate the need for manufacturers to implement good quality control procedures, including regular laboratory nutritional analysis. To encourage this process, interested consumers could request copies of recent independent laboratory nutritional analysis results from manufacturers.

Occasional variation of brands and diets (always using a gradual transition) will decrease risks of nutritional deficiencies – which are less likely to occur across multiple brands, and will also decrease fixation on any particular food type, which may be useful if future health problems, e.g. age-related, require any special diets. Frequent dietary variation may cause adverse gastrointestinal reactions such as diarrhoea, however, and is not recommended.

The health hazards to cats and dogs (and, of course, to ‘food’ animals) that are inherent to commercial meat-based companion animal diets are extensive, and difficult to avoid (see Meat based-diets). Additionally, growing numbers of informed consumers are unwilling to financially support the suffering and death inherent to the meat industry, and the environmental damage it causes. Consequently, growing numbers are exploring vegetarian alternatives.

Regardless of the combination of animal, plant, mineral or synthetically-based ingredients used, diets for cats, dogs, or other species should be formulated to meet the palatability, nutritional and bioavailability requirements of the species for which they are intended. There is no scientific reason why a diet comprised only of plant, mineral and synthetically-based ingredients cannot be formulated to meet all of these needs. In fact, several commercially-available vegan diets aim to do so, and have jointly supported a healthy population of thousands of vegan cats, dogs and ferrets (who are also naturally carnivorous) for many years (Weisman 2004). Regardless of the ingredients used however, sound quality control procedures, including regular laboratory nutritional analysis, should be implemented, to ensure products consistently meet these requirements. Correct use of a complete and balanced nutritional supplement is essential to ensure the health of vegetarian companion animals, particularly cats. 

As always, the health status of all animals should be regularly monitored, including through annual veterinary checkups, or more frequently if illness arises from any cause, with screening blood tests at appropriate intervals in old age, or where otherwise clinically indicated.

• Baker DH, Czarnecki-Maulden GL. Comparative nutrition of dogs and cats. Annu Rev Nutr 1991; 11: 239-263.
• Belfield WO, Zucker M. Very Health Cat Book. New York, NY: McGraw-Hill Book Company. 1983. 153, 198.
• Blood DC, Studdert VP. Bailliere’s Comprehensive Veterinary Dictionary. London: Bailliere Tindall. 1988.
• Burns et al. 1982. In National Research Council. Nutrient Requirements of Cats. Washington, DC: National Academy Press. 1986: 12.
• Dodd, S. A., Dewey, C., Khosa, D., & Verbrugghe, A. (2021). A cross-sectional study of owner-reported health in Canadian and American cats fed meat-and plant-based diets. BMC Veterinary Research, 17(1), 1-16.
• Gillen J. Obligate Carnivore. Seattle, WA: Stein Hoist Books. 2003.
• Gray CM, Sellon RK, Freeman LM. Nutritional adequacy of two vegan diets for cats. J Am Vet Med Assoc 2004; 225(11): 1670-1675.
• Hegsted et al. 1947. In National Research Council. Nutrient requirements of cats. Washington, DC: National Academy Press. 1986: 12.
• Hill’s Pet Nutrition. http://www.hillspet.com/index.jsp, accessed 21 Oct. 2003.
• Hwang SL. The Wall Street Journal. 1993; 27 Oct.: 1.
• Jagger D. No date. Vegepet Gazette. In Peden J. Vegetarian Cats & Dogs. 3rd Edn. Troy, MT: Harbingers of a New Age. 1999.
• James & McCay. 1950. In National Research Council. Nutrient Requirements of Cats. Washington, DC: National Academy Press. 1986: 12.
• Kendall & Holme. 1982. In National Research Council. Nutrient Requirements of Cats. Washington, DC: National Academy Press. 1986: 12.
• Kienzle E, Engelhard R. A field study on the nutrition of vegetarian dogs and cats in Europe. Supplement to Compend Contin Educ Pract Vet 2001; 23(9A): 81.
• Kirk CA, Debraekeleer J, Armstrong PJ. Normal cats. In Hand MS, Thatcher CD, Remillard RL, et al. (Eds.) Small Animal Clinical Nutrition. 4th Edn. Philadelphia, PA: WB Saunders. 2000; 291-351.
• Kuba A. Personal communication to Andrew Knight re: regression of diabetes of his three year old male castrated cat ‘Mussi’ after transitioning from a commercial meat-based to a vegan diet. 17 Aug. 2004.
• Lewis LD, Morris ML, Hand MS. Small Animal Clinical Nutrition. 3rd Edn. Topeka, KS: Mark Morris Associates. 1987.
• Lemmon M. Arthritis help. Sandpoint, ID: Harbingers of a New Age. 1991: 3-5.
• MacDonald ML, Rogers QR, Morris JG. Nutrition of the domestic cat, a mammalian carnivore. Ann Rev Nutr 1984; 4: 521-562.
• MacEwen G. Fat cats and dogs. Petfood Industry. 1989; 31: 28-34.
• Moore et al. 1980. In National Research Council. Nutrient Requirements of Cats. Washington, DC: National Academy Press. 1986: 12.
• National Research Council. Nutrient Requirements of Cats. Washington, DC: National Academy Press. 1986.
• Papich M. 5-minute consult drug formulary. In Tilley LP & Smith FWK. (Eds.) The 5-Minute Veterinary Consult: Canine and Feline. 3rd Edn. Philadelphia, US: Lippincott Williams & Wilkins. 2004. 1391-1456.
• Palackal T, Moretz R, Wisniewski H, Sturman J. Abnormal visual cortex development in the kitten associated with maternal dietary taurine deprivation. J Neurosci Res 1986; 15(2): 223-239.
• Peden J. Vegetarian Cats & Dogs. 3rd Edn. Troy, MT: Harbingers of a New Age. 1999.
• Peden J. Personal communication to Andrew Knight re: feline vegetarian diets and Harbingers of a New Age vegan pet food. 24 Feb. 2004.
• Pencovic & Morris. 1975. In National Research Council. Nutrient Requirements of Cats. Washington, DC: National Academy Press. 1986: 6.
• Petrey S. Absolutely NO-KILL: maintaining a vegan sanctuary. Animals’ Agenda 1998; 18(6): 30-31.
• Plechner AJ, Zucker M. Pet Allergies. Inglewood, CA: Very Healthy Enterprises. 1986: 20.
• Tennant B. Editor in Chief. BSAVA Small Animal Formulary. 4th Edn. Gloucester, UK: British Small Animal Veterinary Association. 2003.
• Thorvin Inc. No date. Uses of kelp. http://www.thorvin.com/uses.htm#feed, accessed 9 Aug. 2004.
• Villar D, Knight MJ, Hansen SR, Buck WB. Toxicity of melaleuca oil and related essential oils applied topically on dogs and cats. Vet Human Toxicol 1994; 36(2): 139-142.
• Westbeau G. Little Tyke. Wheaton, IL: Theosophical Publishing House. 1986.
• Weisman E. Personal communication to Andrew Knight re: Evolution Diet vegan pet food. 24 Feb. 2004.
• Zoran DL. The carnivore connection to nutrition in cats. J Am Vet Med Assoc 2002: 1559-1567.
• Zorn JW. Seaweed and vitality. Popular Library. 1974: 85-86.

The appendices explore topics such as the health status of cats maintained on vegetarian diets long-term, nutrients of particular importance to cats, the potential for nutritional inadequacy in poorly formulated diets, the health hazards that may result.