Vegan diets for cats – a review of the evidence
This technical letter, published in a leading UK veterinary journal, summarised the evidence extant by Oct. 2023, about health outcomes of cats on vegan vs meat-based diets. Three studies had shown equivalent or superior health outcomes, when vegan diets were used.
Knight A (2023). Vegan diets for cats – a review of the evidence. Vet Times 53(41), p. 31.
The relative benefits for environmental sustainability of vegan diets for dogs, cats and people
Environmental impacts of the livestock sector are proportional to consumption levels. To assess the relative consumption of livestock animals within the diets of dogs, cats and peo- ple, this study examined their dietary energy needs within the US in 2020, and globally in 2018. Also studied were US pet food ingredients, and environmental sustainability indicators for plant- and animal-based foods consumed globally. Relative consumptions of average livestock animals were: US: dogs– 17.7%, cats– 2.3%, humans– 80.0%; and globally: dogs– 7.7%, cats– 1.2%, humans– 91.1%. Full transition to nutritionally-sound vegan diets would spare from slaughter the following numbers of terrestrial livestock animals annually (billions): US: dogs– 1.7, cats– 0.2, humans– 7.8, and globally: dogs– 6.0, cats– 0.9, humans– 71.3, as well as billions of aquatic animals in all dietary groups. Very large impact reductions were also associated with land and water use, emissions of greenhouse gases (GHGs), acidifying and eutrophifying gases, and biocide use, in all dietary groups. If imple- mented globally, nutritionally-sound vegan diets would free up land larger than the following nations: dogs–Saudi Arabia or Mexico, cats–Japan or Germany, humans–Russia–the world’s largest country–combined with India. Such diets would save freshwater volumes greater than all renewable freshwater in the following nations: dogs–Denmark, cats–Jordan, humans–Cuba. Such diets would reduce GHGs by amounts greater than all GHG emissions from following nations: dogs–South Africa or the UK, cats–Israel or New Zealand, humans– India or the entire EU. The numbers of additional people who could be fed using food energy savings associated with vegan diets exceeded the 2018 human populations of the following nations: dogs–the entire European Union, cats–France or the UK, humans–every single nation or collective region on Earth, as defined by the World Bank. All of these estimates are conservative.
Knight A (2023) The relative benefits for environmental sustainability of vegan diets for dogs, cats and people. PLoS ONE 18(10): e0291791. https://doi.org/10.1371/journal.pone.0291791.
Vegan versus meat-based cat food:
guardian-reported health outcomes in 1,369 cats, after controlling for feline demographic factors
Increasing concerns about environmental sustainability, farmed animal welfare and competition for traditional protein sources, are driving considerable development of alternative pet foods. These include raw meat diets, in vitro meat products, and diets based on novel protein sources including terrestrial plants, insects, yeast, fungi and potentially seaweed. To study health outcomes in cats fed vegan diets compared to those fed meat, we surveyed 1,418 cat guardians, asking about one cat living with them, for at least one year. Among 1,380 respondents involved in cat diet decision-making, health and nutrition was the factor considered most important. 1,369 respondents provided information relating to a single cat fed a meat-based (1,242–91%) or vegan (127–9%) diet for at least a year. We examined seven general indicators of illness. After controlling for age, sex, neutering status and primary location via regression models, the following risk reductions were associated with a vegan diet for average cats: increased veterinary visits– 7.3% reduction, medication use– 14.9% reduction, progression onto therapeutic diet– 54.7% reduction, reported veterinary assessment of being unwell– 3.6% reduction, reported veterinary assessment of more severe illness– 7.6% reduction, guardian opinion of more severe illness– 22.8% reduction. Additionally, the number of health disorders per unwell cat decreased by 15.5%. No reductions were statistically significant. We also examined the prevalence of 22 specific health disorders, using reported veterinary assessments. Forty two percent of cats fed meat, and 37% of those fed vegan diets suffered from at least one disorder. Of these 22 disorders, 15 were most common in cats fed meat, and seven in cats fed vegan diets. Only one difference was statistically significant. Considering these results overall, cats fed vegan diets tended to be healthier than cats fed meat-based diets. This trend was clear and consistent. These results largely concur with previous, similar studies.
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.
Call for evidence-based positions on vegan diets
This technical letter, published in a leading UK veterinary journal, sheds light on some of the reason for the British Veterinary Association’s repeated opposition to vegan pet food – they appear to be crucially ignorant of key facts concerning this field. At least they’ve stated they will review their position in the future…
Knight A (2022). Call for evidence-based positions on vegan diets. Vet Times 52(29), p. 19.
The weight-of-evidence position on vegan dog food
This technical letter, published in a leading UK veterinary journal, summarised the evidence extant by May 2022, about health outcomes of dogs on vegan vs meat-based diets. Four studies showed equivalent or superior health outcomes for dogs on vegan diets (compared to meat-based dog food), and one study (the oldest, smallest) showed a contrary result.
Knight A (2022). The weight-of-evidence position on vegan diets. Vet Times 52(21), 23.
Vegan versus meat-based dog food: Guardian-reported indicators of health
Alternative pet foods may offer benefits concerning environmental sustainability and the welfare of animals processed into pet foods. However, some worry these may compromise the welfare of pets. We asked 2,639 dog guardians about one dog living with them, for at least one year. Among 2,596 involved in pet diet decision-making, pet health was a key factor when choosing diets. 2,536 provided information relating to a single dog, fed a conventional meat (1,370 = 54%), raw meat (830 = 33%) or vegan (336 = 13%) diet for at least one year. We examined seven general indicators of ill health: unusual numbers of veterinary vis- its, medication use, progression onto a therapeutic diet after initial maintenance on a vegan or meat-based diet, guardian opinion and predicted veterinary opinion of health status, percentage of unwell dogs and number of health disorders per unwell dog. Dogs fed conventional diets appeared to fare worse than those fed either of the other two diets. Dogs fed raw meat appeared to fare marginally better than those fed vegan diets. However, there were statistically significant differences in average ages. Dogs fed raw meat were younger, which has been demonstrated to be associated with improved health outcomes. Additionally, non- health related factors may have improved apparent outcomes for dogs fed raw meat, for three of seven general health indicators. We also considered the prevalence of 22 specific health disorders, based on predicted veterinary assessments. Percentages of dogs in each dietary group considered to have suffered from health disorders were 49% (conventional meat), 43% (raw meat) and 36% (vegan). Significant evidence indicates that raw meat diets are often associated with dietary hazards, including nutritional deficiencies and imbalances, and pathogens. Accordingly, the pooled evidence to date indicates that the healthiest and least hazardous dietary choices for dogs, are nutritionally sound vegan diets.
Knight A, Huang E, Rai N, Brown H (2022) Vegan versus meat-based dog food: Guardian-reported indicators of health. PLoS ONE 17(4): e0265662. https://doi.org/10.1371/journal.pone.0265662.
Vegan versus meat-based pet foods:
owner-reported palatability behaviours and implications for canine and feline welfare
Consumer suspicion of conventional pet foods, along with perceived health benefits of alternative diets, are fuelling development of the latter. These include raw meat diets, in vitro meat products, and diets based on novel protein sources such as terrestrial and marine plants, insects, yeast and fungi. However, some claim vegan diets may be less palatable, or may compromise animal welfare. We surveyed 4,060 dog or cat guardians to determine the importance to them of pet food palatability, and the degree to which their animals displayed specific behavioural indicators of palatability at meal times. Guardians were asked to choose one dog or cat that had been within their household for at least one year, and not on a prescription or therapeutic diet. Of 3,976 respondents who played some role in pet diet decision-making, palatability was the third most important among 12 factors cited as important when choosing pet diets. For 1,585 respondents feeding conventional or raw meat diets, who stated they would realistically consider alternative diets, palatability was the fourth most important among 14 desired attributes. For the 2,308 dogs included, reported observations of 10 behavioural indicators of palatability at meal times reliably indicated significant effects of increased reports of appetitive behaviour by dogs on a raw meat diet, as opposed to a conventional diet. There was no consistent evidence of a difference between vegan diets and either the conventional or raw meat diets. For the 1,135 cats included, reported observations of 15 behavioural indicators indicated that diet made little difference to food-oriented behaviour. Based on these owner-reported behaviours, our results indicate that vegan pet foods are generally at least as palatable to dogs and cats as conventional meat or raw meat diets, and do not compromise their welfare, when other welfare determinants, such as nutritional requirements, are adequately provided.
Knight A and Satchell L, (2021). Vegan versus meat-based pet foods: owner-reported palatability behaviours and implications for canine and feline welfare. PLoS ONE 16(6): e0253292. https://doi.org/10.1371/journal.pone.0253292.
The nutritional soundness of meat-based and plant-based pet foods
Global trends such as population growth, increasing competition for protein sources, environmental degradation, and farmed animal welfare concerns, are all driving plant-based pet food development. However, lack of evidence of nutritional sufficiency is inhibiting their uptake. This interferes with the ability of some consumers to adopt pet foods more aligned with their values, and the ability of the pet food sector to fully realise the potential of this emerging market, whilst concurrently reducing its environmental footprint. Yet, no systematic study has been published examining the prevalence of steps taken to ensure the nutritional soundness and quality of pet foods, and whether plant-based diets have lower standards in these respects. Accordingly, we designed a study to explore this.
Materials and methods
We surveyed pet food manufacturers producing 19 meat-based and 10 vegan, almost vegan or vegetarian pet foods.
Although there were there were limited areas in which practices could be improved, most manufacturers had acceptable or superior standards at nearly all stages examined, throughout the design, manufacturing, transportation and storage phases, with plant-based diets slightly superior to meat-based diets overall.
A range of best practice steps should be implemented by companies and regulators, and a comprehensive range of communication modalities implemented, to reassure consumers about the nutritional soundness of products.
Knight A and Light N. (2021). The nutritional soundness of meat-based and plant-based pet foods. Revista Electronica De Veterinaria 22(1), 1 – 21.
Vegetarian Versus Meat-based
Diets for Companion Animals
Many owners of companion animals are interested in vegetarian diets for their animals, as concerns increase about the consequences of animal farming, for health, animal welfare, and the environment. However, are vegetarian diets for cats and dogs nutritionally balanced and healthy? This article comprehensively reviews the evidence published to date from four studies that have examined the nutritional adequacy of vegetarian diets for cats and dogs. To obtain additional information, we surveyed 12 pet food companies detailed in the most recent study. We also examined the nutritional soundness of meat-based companion-animal diets, and reviewed the evidence concerning the health status of vegetarian, carnivorous and omnivorous companion animals. Both cats and dogs may thrive on vegetarian diets, but these must be nutritionally complete and reasonably balanced. Owners should also regularly monitor urinary acidity, and should correct urinary alkalinisation through appropriate dietary additives, if necessary.
Knight, A. and Leitsberger, M. (2016). Vegetarian versus meat-based diets for companion animals. Animals 6, 57.
Vegan Diets for Companion Animals
Circulation 1.2 million people.
Knight A (2018). Vegan diets for companion animals. The Healthy Pet Guide. Distributed with The Mail on Sunday, 14 Oct. 50 – 51.
How to Safely Veganise Your Cat or Dog
One page summary by the Vegan Society (New Zealand).
Knight A (2018). How to safely veganise your cat or dog. Green for Life, winter. 16.
A humorous, thought-provoking examination of the controversial issue of vegan diets for cats and dogs. Includes a discussion of the health hazards and benefits of meat-based and vegan diets, a discussion of natural feeding behaviour, and advice for guardians of vegan animals on safeguarding their health.
Knight A (2008). Fishy business? Lifescape, May, 74-76.
Vegan Animal Diets: Facts and Myths
A summary published on The Vegan Society (UK) website.
Knight A (2015). Vegan animal diets: facts and myths. The Vegan Society [UK].
Debate About Vegan Cat Food
a series of letters in J Amer Vet Med Assoc, 2005.