Review of more than 30 studies finds vegan dog and cat food generally well digested

A comprehensive scientific review has found that nutritionally complete vegan and vegetarian pet diets are generally well digested by both dogs and cats and perform similarly to conventional meat-based diets.The review, published in the journal Animals, analyzed 31 previously published studies evaluating the digestibility of plant-based, vegetarian, and vegan diets and ingredients for companion animals. Of the studies included, 22 focused on dogs, two on cats, and seven evaluated both species.

Digestibility is a critical measure in animal nutrition because it determines how efficiently nutrients are broken down, absorbed, and utilized by the body. Even when a diet contains all essential nutrients, poor digestibility can limit the amount of nutrition an animal actually receives.

According to lead author Professor Andrew Knight, an animal welfare researcher affiliated with Griffith University's School of Environment and Science, the evidence challenges the common belief that dogs and cats cannot efficiently digest plant-based proteins.

"Current evidence indicates nutritionally sound vegan and vegetarian pet diets, and their main protein sources, are generally well digested by dogs and cats," said Professor Knight.

A Wide Variety of Plant Proteins Studied

The review evaluated numerous protein sources commonly used in modern vegan pet foods, including:

• Wheat gluten

• Rice protein

• Soy-based proteins

• Peas

• Lentils

• Chickpeas

• Potato protein

• Quinoa

• Microbially fermented proteins

Researchers also examined commercially available vegan dog foods containing ingredients such as peas, barley, oats, sunflower oil, and lentils.

Overall, digestibility remained high across the studies. Although some individual plant ingredients showed slightly lower digestibility than comparable animal-derived ingredients, the differences generally did not reduce the overall nutritional quality of well-formulated diets.

What To Look For

Professor Knight emphasized that not all vegan pet foods are created equally. He recommends choosing diets that are clearly labeled as nutritionally complete and manufactured by reputable companies that work with veterinary nutritionists and conduct quality assurance testing.

"These findings support the use of carefully formulated vegan and vegetarian diets and challenge the notion that such diets are less digestible than conventional meat-based diets," he said.

He also advised pet owners to verify that manufacturers can explain how they ensure nutritional adequacy and formulation quality.

More Research Needed

While the evidence supporting digestibility is encouraging, the authors note that additional research is still needed—particularly for:

• Cats in everyday home environments

• Kittens

• Senior pets

• Animals with underlying medical conditions

Further studies will help determine how these diets perform over the long term in a broader range of animals.

The review, "The Digestibility of Vegan and Vegetarian Diets for Dogs and Cats," was published in the journal Animals.