### Review of the Literature For a long time, public perception of vegan diets, for both human and non-human animals, has been negative and fraught with misinformation. Historically, cats could not be vegan due to human's inability to synthesize key nutrients that cats need in their diet. Recent advancements in food science have challenged these long-held assumptions, and the past three decades of research point to the sustainability of a long term vegan diet for cats and dogs (Dominguez-Oliva et al., 2023). For many, the ability for dogs to be maintained on a long term vegetarian diet is less contentious, so the primary focus of this article will be cats, but many of these sources also support and defend vegan dogs (Brown, 2009; Brown et al., 2009; Dominguez-Oliva et al., 2023; Knight et al., 2024). Cats lack the genes necessary to synthesize 6 key vitamins and nutrients (Gray et al., 2004; Knight & Leitsberger, 2016). As long as any vegan food is supplemented with those nutrients and has a relatively high protein/fat content, there is no other physical reason they cannot be vegan (Knight & Leitsberger, 2016; Semp, 2014; Dodd et al., 2021; Dominguez-Oliva et al., 2023, Knight et al., 2023). Furthermore "a significant and growing body of population studies and case reports have indicated that cats and dogs maintained on vegetarian diets may be healthy—including those exercising at the highest levels—and, indeed, may experience a range of health benefits. Such diets must be nutritionally complete and reasonably balanced" (Knight & Leitsberger, 2016). "Wakefield and colleagues (2006) compared the health of 34 cats maintained on vegetarian diets for at least a year, with that of 52 cats maintained on meat-based diets for at least a year. There were no significant differences in age, sex, body condition, housing, or perceived health status, with most cats described as healthy or generally healthy. These results are hardly surprising, when we consider that animals need specific nutrients, not ingredients. There is no scientific reason why a diet comprised only of plant, mineral and synthetically-based ingredients cannot be formulated to meet all of the palatability, nutritional and bioavailability needs of the species for which it is intended". Wakefield and colleagues in this study also performed blood tests on a portion of these cats and did not find serum concentration of key nutrients to be outside of normal ranges. One study looking at vegan cats even found that "no ... significant deviations from normal values were observed. In particular, lower values of iron, protein or vitamin B12 in vegan cats were not observed" (Knight & Leitsberger, 2016). There was a systematic review published in 2023 covering all the available literature on the topic of both cats and dogs being fed vegetarian diets. Although many of these studies consist of owner-reported information, some used blood tests to confirm serum concentrations of several nutrients, and positive outcomes for cats fed plant-based diets were consistent across many studies, and thus the outcomes should not be ignored or downplayed (Dominguez-Oliva et al., 2023). ### Necessary Nutrients for Cats The six vitamins and nutrients mentioned above that cats need supplemented in their food are as follows, as well as recommendations from the AAFCO for minimums for every 1000 kcal of food: Vitamin D (70 IU) Vitamin B12 (5 µg) Vitamin A (800 IU - 1600 IU) Taurine (250 mg for dry food; 500 mg for wet food) Arachidonic acid (AA) (50 mg or (0.02%) Eicosapentaenoic Acid (EPA) (30 mg or 0.012%) Note that AA and EPA are both Omega 3's. Additionally, you will want to consider the ratios of macronutrients. To be considered nutritionally complete and balanced, the AAFCO mandates that a cat food for adult maintenance contain a minimum of 26% crude protein on a dry matter basis. The minimum for growth and reproduction is 30%. The AAFCO states that higher protein content than the minimums when possible is beneficial. The AAFCO minimum for fat in all cat foods is 9% on a dry matter basis, although a true requirement for crude fat has not been established. Ami Cat Food To take a specific example, Ami has a cat food that has the following micro- and macro-nutrient profile: 3,760 kcal/kg Crude protein 33.00% Crude fat 13.00% Crude fiber 3.50% Omega-3 fatty Acid 0.41% Omega-6 fatty Acid 5.41% Per 1000 kcal of Food: Vitamin A 6382 IU Vitamin D3 400 IU Taurine 400 mg Benevo also has a similar nutrient profile, although their data is listed per kilogram of food instead of per 1000kcal of food. ### Urinary Crystals If you are worried about urinary crystals (uroliths), there exists litter that can check a cat's urine pH. There are three main types of uroliths: struvite uroliths, calcium oxalate uroliths, and urate uroliths (Forrester & Roudebush, 2007). The treatment for each is different. For all of these, increasing water intake is the most important thing to do. **Struvite Urolithiasis** To induce dissolution of struvite urolithiasis, a calculolytic diet aimed to decrease the pH of a cat's urine is used. Other important factors for dissolving and reducing urolith formation of this type is avoiding excess magnesium and phosphorus in the diet and increased salt consumption to induce more dilute urine (AAFCO; Forrester & Roudebush, 2007). Methionine and vitamin C supplementation can lower the pH of a cat's urine, but speak to a veterinarian prior to starting this type of supplementation to get blood tests. Too low of a urine pH can also be bad. An easy supplement to find online for cats are cranberry treats, as they contain vitamin C. **Calcium Oxalate Urolithiasis** For this type, increasing the pH of a cat's urine is indicated. Additionally, higher fiber food has been shown to help with this (Forrester & Roudebush, 2007). For this type of urolith, vitamin C supplementation should be avoided, as you want to increase urine pH. Potassium citrate is often indicated for this subtype. Again, speak to a veterinarian before supplementing to get appropriate blood work done to fully understand what should be done. ### Obligate Carnivores The term obligate carnivore is only relevant when talking about wild animals because it is related to their nutrient requirements in a diet they could naturally acquire in the wild, but because humans can give cats supplemented and appropriately designed food, it is not an issue in domesticated animals (Knight & Leitsberger, 2016). Taurine from animal sources is chemically identical to taurine synthesized in a lab. If macro- and micro- nutrients are in the range necessary for feline life, then the source is not relevant. ### Plant-Based Food Companies Below I will link to several different pet food companies that offer vegan cat or dog food for anyone to look into and compare. Two well-known and respected companies are Benevo and Amì. ### References Benevo – Animal friendly animal foods.  http://www.benevo.com/ Amì Cat Food.  https://www.amipetfood.com/en/products/products-for-cats/amicat Brown, W. (2009). Nutritional and ethical issues regarding vegetarianism in the domestic dog. https://www.une.edu.au/__data/assets/pdf_file/0015/30471/brown-raan-2009-vegetarian-dog.pdf Brown, W. Y., Vanselow, B. A., Redman, A. J., & Pluske, J. R. (2009). An experimental meat-free diet maintained haematological characteristics in sprint-racing sled dogs. Br J Nutr, 102(9), 1318-1323. https://doi.org/10.1017/S0007114509389254 Dodd, S. A. S., 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 Vet Res, 17(1), 53. https://doi.org/10.1186/s12917-021-02754-8  Dominguez-Oliva, A., Mota-Rojas, D., Semendric, I., & Whittaker, A. L. (2023). The Impact of Vegan Diets on Indicators of Health in Dogs and Cats: A Systematic Review. Vet Sci, 10(1). https://doi.org/10.3390/vetsci10010052  Forrester, S.D., & Roudebush, P. (2007). Evidence-based management of feline lower urinary tract disease. Vet Clin North Am Small Anim Pract, 37(3), 533-558. https://doi.org/10.1016/j.cvsm.2007.01.009 Evolution Diet.  https://petfoodshop.com/ Knight, A. (2005). In defense of vegetarian cat food. https://www.researchgate.net/publication/7990724_In_defense_of_vegetarian_cat_food Knight, A., Bauer, A., & Brown, H. (2023). Vegan versus meat-based cat food: Guardian-reported health outcomes in 1,369 cats, after controlling for feline demographic factors. PLoS One, 18(9), e0284132. https://doi.org/10.1371/journal.pone.0284132  Knight, A., Bauer, A., & Brown, H. (2024). Vegan versus meat-based dog food: Guardian-reported health outcomes in 2,536 dogs, after controlling for canine demographic factors. Heliyon, 10(17), e35578. https://doi.org/10.1016/j.heliyon.2024.e35578 Knight, A., & Leitsberger, M. (2016). Vegetarian versus Meat-Based Diets for Companion Animals. Animals, 6(9), 57. https://doi.org/10.3390/ani6090057  Semp, P.-G. (2014). Vegan Nutrition of Dogs and Cats https://www.vetmeduni.ac.at/hochschulschriften/diplomarbeiten/AC12256171.pdf Vecado. Vegan Cats 101: nutrients, not ingredients is what really matters. https://vecado.ca/pages/cats101 Wakefield, L. A., Shofer, F. S., & Michel, K. E. (2006). Evaluation of cats fed vegetarian diets and attitudes of their caregivers. J Am Vet Med Association, 229(1), 70-73. https://doi.org/10.2460/javma.229.1.70