Nutrition Research

Can plant-based canine diets provide complete nutrition?

Dogs (like humans) do not have a dietary requirement for any specific ingredients, but rather need to consume appropriate amounts of 35+ essential nutrients. Essential nutrients include proteins, fats, vitamins, and minerals that must be provided by the diet. Many nutrients can be endogenously produced - i.e. created from other nutrients and substances within the body - so only a subset that form the ‘building blocks’ and cannot be produced internally are considered essential.  

U.S. (AAFCO) and European (FEDIAF) regulatory agencies establish nutritional profiles that include minimum (and sometimes maximum) amounts of every essential ingredients dogs require based on a consensus of current nutritional research. Every dog food that is labeled as “complete and balanced” for dogs of that life stage must meet those nutritional profile requirements for essential nutrients. Those guidelines provide the acceptable range, which allows for very different macronutrient approaches (e.g. high meat, low carb and meat-free, high fiber) that all meet the standards. Choosing certain ingredient restrictions - like eliminating animal-derived products - can create areas of focus for diet formulators to ensure that all nutrients are present in sufficient amounts. 

Resources

Plant-based diets for dogs (Dodd 2018): Journal of the American Veterinary Medical Association

Are plant-based diets "biologically appropriate"?

One way to understand the nutritional effects and suitability of different diets is through dogs’ digestive response and physiology. Certain enzymes can break down and digest different macronutrients, and the presence (or lack of) digestive substances can be a critical first indication of nutritional impact. 

One of the essential nutritional questions is whether the nutrient in the food can actually be incorporated into the body. Digestibility refers to the efficiency with which the nutrients in food are absorbed. High digestibility is not necessarily a good thing as many beneficial nutrients like dietary fiber are inherently difficult to digest. Ultra-processed foods are often extremely digestible because they’ve been stripped of fiber and broken down into simple starches and sugars.

Dogs digest common plant-based ingredients - and their proteins - at a high rate.
Experimental digestibility studies have measured the total digestibility, protein digestibility, and specific amino acid digestibility of different plant-based canine diets, including fresh vegan diets. The digestibility of the tested plant-based canine formulas are consistently high and often higher than traditional meat-inclusive kibble. 

Dogs have evolved to digest starch and carbohydrates at higher rates than their common wolf ancestor.
Dogs developed significant genetic adaptations to digest starches with high efficiency, which occurred at the same time that humans began large-scale cultivation of cereals ~3,000-5,000 years ago. The enhanced ability to derive nutrients from carbohydrates is one of the primary genetic differences between companion dogs and wolves. 

Dogs have eaten plant-rich diets for thousands of years.
Archeological evidence support the hypothesis that dogs consumed diets that were highly correlated with the diets of local humans (either intentionally prepared for the dogs or as scavenged trash), including consuming almost entirely plant-based diets in Europe and the Middle East where meat was rare and costly and humans primarily subsisted on grains and legumes. Interestingly, even wolves eat more plants and human food than conventional wisdom would suggest, and particularly those that live in close proximity to humans.

While dogs are members of the order Carnivora (i.e. they are carnivorans), they are not obligate carnivores.
Most dogs are opportunistic scavengers and will eat food that is available. Many carnivorans have distinct dietary habits, including omnivorous scavengers like raccoons and even herbivorous panda bears that began consuming protein almost exclusively through plant-based sources in the last 5,000-10,000 years.

Resources

Amino acid digestibility and nitrogen-corrected true metabolizable energy of mildly cooked human-grade vegan dog foods using the precision-fed cecectomized and conventional rooster assays Roberts et al. 2023

The genomic signature of dog domestication reveals adaptation to a starch-rich diet (Alexsson et al. 2013)
Dogs that ate plants: changes in the canine diet during the late Bronze Age and the first Iron Age in the northeast Iberian Peninsula, Journal World Prehistory, March, 2021. DOI: https://doi.org/10.1007/s10963-021-09153-9. 

Zlatanova, Diana & Ahmed, Atidzhe & Vlasseva, Albena & Genov, Peter. (2014). Adaptive Diet Strategy of the Wolf (Canis lupus L.) in Europe: a Review. Acta Zoologica Bulgarica. 66. 439-452.

Can dogs thrive on a plant-based diet?

A significant evidence base of clinical, experimental, and epidemiological analyses demonstrates that a properly formulated (AAFCO-compliant) plant-based diet provides dogs with equivalent - and even superior - health outcomes compared to dogs eating a meat-inclusive diet.

Owners of dogs eating plant-based diets have consistently reported better health outcomes - and even a longer average lifespan -  than dogs on traditional meat-inclusive diets. A 2022 analysis of owner-reported health information for more than 1,400 dogs found that dogs eating plant-based diets had longer reported lifespans (>1  additional year) and fewer reported health issues than dogs that consumed traditional diets. Another study that included over 2,500 dogs found that dogs eating plant-based diets had fewer reported health issues - including irregular veterinary visits and medication use - than dogs eating conventional meat-inclusive diets. While owner-reported health data have bias and accuracy issues, owner-reported metrics are widely used in veterinary epidemiology as the most accessible form of population health information and lack of standardized health (or death) records in veterinary care.

Resources

Domestic dogs maintain positive clinical, nutritional, and hematological health outcomes when fed a commercial plant-based diet for a year.
Annika Linde, Maureen Lahiff, Adam Krantz, Nathan Sharp, Theros T. Ng, Tonatiuh Melgarejo
bioRxiv 2023.02.18.525405; doi: https://doi.org/10.1101/2023.02.18.525405

Abstract: Domestic dogs can maintain health on complete and well-balanced canine plant-based nutrition (K9PBN). Novel insight on health outcomes in dogs consuming K9PBN is of relevance to veterinary professionals and consumers given a growing interest in non-traditional dog foods with perceived health benefits, while considering potential safety concerns. We aimed to investigate nutritional equivalence by measuring clinical health outcomes in adult dogs fed K9PBN over twelve months compared to a meat-based diet at baseline. Clinically healthy, client-owned, adult dogs maintain health, based on physical exams, CBC, serum chemistry, plasma amino acids, serum vitamins, and cardiac biomarkers combined with client-reported observations, when fed commercial K9PBN over a twelve-month period. This study is the most comprehensive and longest known K9PBN investigation to date. It provides clinically important evidence-based nutrition data and new knowledge on outcomes in clinically healthy dogs who maintain health without consumption of animal-derived ingredients. Also, it is of major relevance to One Health paradigms since ingredients produced independent of industrial food animal production are both more sustainable and help to circumvent ethical dilemmas for maintenance of health in domestic dogs.

An experimental meat-free diet maintained haematological characteristics in sprint-racing sled dogs
Brown, W., Vanselow, B., Redman, A., & Pluske, J. (2009). British Journal of Nutrition, 102(9), 1318-1323. doi:10.1017/S0007114509389254

Abstract: A dog's nutrient requirements can theoretically be met from a properly balanced meat-free diet; however, proof for this is lacking. Exercise places additional demands on the body, and dogs fed a meat-free diet may be at increased risk of developing sports anaemia. We hypothesised that exercising dogs would remain in good health and not develop anaemia when fed a nutritionally balanced meat-free diet. To this end, twelve sprint-racing Siberian huskies were fed either a commercial diet recommended for active dogs (n 6), or a meat-free diet formulated to the same nutrient specifications (n 6). The commercial diet contained 43 % poultry meal, whereas soyabean meal and maize gluten made up 43 % of the meat-free diet, as the main protein ingredients. Dogs were fed these diets as their sole nutrient intake for 16 weeks, including 10 weeks of competitive racing. Blood samples were collected at weeks 0, 3, 8 and 16, and veterinary health checks were conducted at weeks 0, 8 and 16. Haematology results for all dogs, irrespective of diet, were within normal range throughout the study and the consulting veterinarian assessed all dogs to be in excellent physical condition. No dogs in the present study developed anaemia. On the contrary, erythrocyte counts and Hb values increased significantly over time (P < 0·01) in both groups of dogs. The present study is the first to demonstrate that a carefully balanced meat-free diet can maintain normal haematological values in exercising dogs.