Written by: Heather Clemenceau
Cats have evolved into a highly specialized hunter, who has been more lightly impacted by domestication relative to dogs. As an obligate carnivore, they rely on their prey to supply most of their nutritional needs as they lack sufficient enzymes to synthesize their metabolic requirements. Cats are designed to extract their nutrients from meat, not from plants, and any nutritional deficiencies that may result from an inadequate diet often take months or years to manifest themselves, by which time a disease condition may be irreversible. This is why it’s important for cat owners to mimic the high-protein, low-carb diet cats would source for themselves (rather like the high protein,low-carb diet developed by cardiologist Dr. Atkins).
Cats – Evolutionarily Positioned To Eat Meat
What evidence do we have that cats are strictly meat eaters? Cats are obvious hunters – they have high visual acuity and an acute sense of hearing. Like all predator species, their ears and eyes face forward to detect prey. Their claws are normally retracted while stalking, to mask their movements as much as possible. Cats teeth are ideal for immobilizing the spinal column of the small prey animals they would typically hunt in the wild, and their small stomachs are adapted for smaller meals, approximately the size of mice. They also prefer their food at roughly the same temperature as that of freshly killed prey. Feeding behaviours evolved in cats include searching for food during both day and night, which corresponds with the activity of their traditional prey animals.
A wild or feral cat WILL eat some plant matter in the G.I. tract of smaller animals they kill and swallow mostly intact. If they catch larger prey, like baby rabbits, they would likely not eat the grassy stomach contents. The plant material in the guts of prey animals is a very small amount of their food intake and in any case, these plant materials are very different from the metabolically high-glycemic carbs offered in vegan cat food.
What It Means To Be An “Obligate Carnivore”
All protein is made from only 21 different amino acids. Cats are able to synthesize only 12 amino acids, so there are 9 amino acids that must be obtained directly directly from their diet. In the case of vegetarian and vegan diets, the amino acids, vitamins and minerals must be heavily supplemented, and thus come from synthetic or lab-created sources (because otherwise most would not be vegan). This is not ideal, since the food must be more highly processed than foods that naturally contain these amino acid requirements. While dogs have evolved (thanks to living closely with humans for 10,000+ years) the ability to eat a more starchy diet comprised of about 30% from protein, cats require that their diet consist of about 52% from protein. This requirement is similar to that of wild exotic cats.
A meat-based diet supplies abundant taurine; cereals and grains supply only marginal or inadequate levels of taurine for cats. Therefore, diets based on these types of protein sources will need supplementation. Three disease states have been identified related strictly to taurine deficiency; feline central retinal degeneration, reproductive failure and impaired fetal development and feline dilated cardiomyopathy. Clinical signs of taurine deficiency occur only after prolonged periods of depletion (from 5 months to 2 years).
Cats do not possess salivary amylase, which begins digestion of carbohydrates and starches in the mouth while chewing. If they are forced to consume carbohydrates this places the burden on their pancreas, which can only produce amylase comparable to about 5% of that of dogs. Cats have very low liver glucokinase activity and therefore limited ability to metabolize carbs by this route either.
The cat is unable to convert beta-carotene to vitamin A due to a lack of intestinal enzymes necessary for the conversion, and therefore cats requires a dietary source of vitamin A. Because vitamin A is a fat-soluble vitamin and is stored in the liver, any deficiencies are slow to develop, and are only seen in cats with severe liver failure. Cats also lack sufficient enzymes to meet the metabolic requirements for vitamin D photosynthesis in the skin; therefore they require a dietary source of vitamin D. Cats need increased amounts of many dietary water-soluble B vitamins, including thiamin, niacin, and other B vitamins. The requirement for niacin and pyridoxine is four times higher than that for dogs.
Sweet Taste Receptors
Taste receptors reflect a species’ food choices. Cats are missing the genes that code for part of the “sweet” taste receptors that recognize carbohydrates. This explains the indifference that domestic cats and their wild relatives lions and tigers, etc. show towards sweet foods. And it may also explain why they have evolved into such accomplished hunters. It makes sense that their taste preferences evolved to ensure they consume an appropriate source of the right calories and that they avoid unsuitable foods.
Nutritional Inadequacies in Vegan Cat Foods
When I first began blogging about vegan cat diets, there was a dearth of information about the long-term effects of carb diets for cats. But now, studies are being carried out as vegan diets increase in popularity. A study published in January 2020 tested several vegan pet foods for dogs and cats available in the Brazilian marketplace, for the purposes of evaluating the macronutrient composition, fatty acid and amino acid profiles, and essential mineral content. The results were then compared with FEDIAF (2019) and AAFCO (2019) recommendations.
“The cat food presented potassium content lower than recommended. The Ca:P ratio did not meet the minimum recommendation of FEDIAF (2019) and AAFCO (2019) in any of the dog’s foods analyzed, and the cat food also did not present the minimum recommendation based on FEDIAF (2019). Copper concentrations exceeded the legal limit in all foods. Zinc concentrations exceeded this limit in two foods (one for dogs and one for cats). the cat food did not meet the minimum recommendation for arginine. In addition, when the amount of nutrients consumed by animals with low energy requirements was simulated, in addition to the same non-conformities described above, it was observed that the cat food does not meet the minimum recommended of protein and taurine in unit/Kg0.67. therefore, these foods should not be recommended for dogs and cats, because dietary deficiencies found may lead to health risks for dogs and cats. Furthermore, manufacturers should review their formulations to ensure the nutritional adequacy of these foods.”
And Some Vegan Cat Foods Are Not Truly Vegan At All….
This 2016 study found that half of the vegan dog and cat foods tested (7/14) were positive for the undeclared DNA of cows, pigs, and sheep. Not only should this raise concern for vegans who believe they are feeding an entirely vegan diet, it tells us that food manufacturers have issues with quality control and adherence to diet profiles. And this was not a one-off occurrence either – the tests were repeated some months apart and the same observations about unintentional adulteration were found.
So the lessons learned here are that vegan or supposedly vegan cat foods are a somewhat of a wildcard – food processing lacks control and food manufacturers evidently do not review their own products for compliance with recommendations for nutrition/protein. Maybe cats are getting a subsistence level of nutrients from these not-vegan foods which is why more cats do not appear to be unhealthier, at least not initially. But even so, it’s very doubtful that the cats can truly appreciate the carbohydrate-derived foods because they don’t have taste receptors for it. To them, it might taste only marginally better than eating flavourless cardboard, which might be why Evolution Pet Food’s founder Eris Weisman advises that cats may need to be “starved” for a few days in order to appreciate his company’s food. I hope that if you were considering giving your cat vegan foods that you at least read that statement and give it some serious reconsideration.
As a vegan, I can completely relate to the desire to minimize the environmental impacts of dog and cat food diets. While feeding a vegan diet to a carnivore is ethically consistent with animal rights philosophy, the specific physiological and behavioural requirements of cats mean that such long-term diets are really an uncontrolled experiment, with our cats as the test subjects. Despite the dramatic anecdotal claims made by some proponents of these diets, there is STILL insufficient evidence showing a benefit (or lack of harm) in feeding vegan diets.