by Jenny Mace, Visiting Scholar, Centre for Ethics, Philosophy and Public Affairs, University of St Andrews, UK & Andrew Knight, Adjunct Professor, College of Environmental and Life Sciences, Murdoch University, Australia
A recently published scientific review has found that vegan and vegetarian diets for dogs and cats are generally as well digested as conventional meat-based diets. It addresses a common consumer concern about vegan petfood: that dogs and cats cannot adequately digest and absorb plant-based ingredients.
The review pooled results from 31 studies conducted since 2000 that examined how well dogs and cats digest vegan or vegetarian diets, or the vegan protein sources most commonly used in them. Across a wide range of study designs, populations and ingredients, digestibility values for vegan diets consistently appeared comparable to those recorded for conventional meat-based diets.
A fast-growing, values-driven market
Nutritionally sound vegan dog and cat food is attracting increasing interest from pet carers concerned about their pet’s health, the environmental footprint of meat-based diets and the welfare of farmed animals reared to produce petfood ingredients. Market figures reflect this shift.
According to Allied Market Research and Future Market Insights, the global vegan petfood market grew from around US$10 billion in 2020 to approximately US$27 billion in 2024. The vegan petfood market is projected to more than double again to US$57 billion by 2034. This constitutes a compound annual growth rate of 7.8 percent, faster than the traditional petfood market as a whole. Significantly, plant-based product launches rose sharply from just nine in 2020 to 57 in 2024.
Is vegan petfood nutritionally sound?
One recurring concern has been whether vegan petfoods can be formulated and manufactured to be nutritionally sound for both dogs and cats. Two recent research studies have directly examined this question.
The first, an industry survey of petfood manufacturers, examined the practical steps companies take, across design, manufacturing, transportation and storage, to safeguard nutritional quality. It found that manufacturers of plant-based petfoods generally met the standards used in meat-based petfood manufacturing. In fact, they performed slightly better overall.
The second is a 2026 systematic review of 54 studies assessing whether commercially available dog and cat food meets the nutrient levels published by authorities such as the Association of American Feed Control Officials, the European Pet Food Industry Federation and the National Research Council.
The picture it paints is sobering for the industry as a whole, as over 80 percent of the studies found at least one nutrient deficiency or excess in the petfoods sampled, regardless of diet type. Various diet types were considered for both dogs and cats, including moist, dry, conventional meat-based, raw meat-based, insect-based and vegan diets. Crucially, vegan petfoods were not found to be at greater risk of nutritional flaws than their meat-based counterparts, when considered overall. In terms of their fatty acid profiles and selenium levels, vegan diets in the review also tended to show more favourable results than conventional diets.
Where does digestibility fit in?
Even a diet that is well formulated and manufactured is only as good as the body’s ability to absorb and utilise it. This is where digestibility becomes important. It is a key determinant of bioavailability—the extent to which nutrients can actually reach an animal’s cells and be put to use, rather than passing through the body undigested. A petfood can include and list all necessary nutrients on its labelling, but if those nutrients are not adequately absorbed, the diet may still fall short.
This is where scepticism about vegan petfood has sometimes concentrated. Some concerns have centred on ‘anti-nutritional factors’, such as phytates and trypsin inhibitors. Some of these are only found in plant ingredients and have the potential to interfere with the absorption of certain minerals and proteins. There are also concerns about higher fibre content in vegan food. Fibre may bind to bile acids and reduce fat absorption. Additionally, as dogs and cats have relatively short digestive tracts, concern also arises from the more limited opportunities for nutrient absorption.
Hence, concerns have been voiced about whether these factors might meaningfully compromise dogs’ and cats’ ability to extract nutrition from vegan diets. This is particularly the case for cats due to their categorisation as obligate carnivores. However, this categorisation refers to evolutionary adaptions to a prey-based ecological niche, not to obligations to consume animal-based ingredients within modern, household environments. Nevertheless, such concerns have led many to ask whether plant-based petfoods can be adequately digested by cats and dogs.
How is digestibility measured?
Digestibility is not studied using a single, uniform measurement. Some studies within the recent review assessed total tract digestibility, which measures nutrient absorption across the entire digestive system, from ingestion to faecal excretion.
Others measured ileal digestibility, which calculates absorption by the end of the small intestine, before food reaches the large intestine, where microbial fermentation can alter the picture. This is normally considered more accurate, especially when considering protein digestion, since most protein digestion occurs before that point.
Studies also varied in whether they reported apparent, standardised or true digestibility. This depended on whether they accounted for the small, unavoidable losses of endogenous material that occur regardless of diet. For instance, routine intestinal cell loss and digestive secretions (e.g., enzymes, mucus) can ultimately end up in an animal’s faeces. This affects measures of nutrient digestibility, such as protein digestibility, because nutrients in the faeces may originate from endogenous material rather than undigested food. True digestibility, which adjusts for both baseline and diet-related endogenous losses, is considered the most precise of the three.
Digestibility study types
The 31 studies included in the digestibility review were grouped into two broad categories. The first comprised seven studies that directly compared the digestibility of vegan or vegetarian diets with conventional (meat-based) formulations. The second category, comprising the remaining studies, examined the digestibility of specific vegan protein sources.
The following macronutrients, compositional factors and nutritional attributes were assessed: dry matter, organic matter, protein (including amino acids), fat, nitrogen-free extract and energy. There was a particular focus on soy due to its extensive scientific comparisons with poultry protein, which is the most common animal-based protein source used in commercial petfood. While the studies comprised predominantly dog-focused studies, nine were either exclusively focused on cats or included both dogs and cats.
What the evidence shows
The results appeared strikingly consistent overall. In the studies that measured the apparent total tract digestibility of vegan diets, values exceeded 80 percent for dry matter, 85 percent for organic matter, 80 percent for crude protein, 89 percent for fat, 88 percent for nitrogen-free extract and 86 percent for energy. These figures are broadly comparable to and in some individual cases marginally higher than, those recorded for meat-based diets in the same studies. Where differences did emerge, they tended to be small, inconsistent in direction and outweighed by the overall similarity between diet types. Results were also comparable in the few studies that considered the more accurate apparent ileal digestibility.
When assessing individual ingredients, the picture was very similar. Soy-derived proteins, examined in more than 20 studies since 2000, showed digestibility values that frequently exceeded 80 percent for dry matter, organic matter and crude protein and 90 percent for fat.
These figures were sometimes lower than poultry protein, and sometimes higher, but consistently showed good digestibility. Both dog and cat food, and both apparent total tract digestibility and apparent ileal digestibility, featured among these studies. Other plant protein sources, including those derived from peas, lentils, chickpeas, faba beans and microbial fermentation, showed similarly strong digestibility. In several cases, they matched or exceeded the digestibility of the animal-based proteins against which they were compared.
Implications for manufacturers
Taken together, this evidence points to dog and cat health being safeguarded when fed modern, commercially sourced (rather than home-made), nutritionally sound vegan diets. However, as described in the manufacturer survey referred to above, good practice steps including careful formulation utilising nutritional experts, careful ingredient sourcing and quality control throughout production are all essential. Dogs and cats have specific, essential dietary nutrient requirements. They both require a defined set of amino acids, along with particular macronutrients, vitamins and minerals, with cats having additional needs to those of dogs.
Some of these nutrients can be degraded by the heat and pressure involved in extrusion and other processing methods, and some can simply vary even among different sources of the same ingredient. Some nutrient levels also degrade with time.
This means post-processing supplementation is often necessary for petfoods of all kinds to ensure the finished product still meets all nutritional requirements, both when shipped and when it eventually arrives in customers’ homes. Stringent ongoing quality assurance checks should be utilised to provide reassurance to manufacturers and customers alike.
Consumer-facing educational outreach about the growing scientific evidence supporting nutritionally sound plant-based diets for dogs and cats, as well as the steps companies are taking to ensure the quality and nutritional content of pet diets, could help petfood companies respond to growing consumer demand for more sustainable diets.
For references, contact editorial@perendale.co.uk
