Andrew Knight review finds vegan pet food digests as well as meat-based diets

A review of 31 scientific studies has concluded that nutritionally complete vegan and vegetarian pet foods are generally as digestible as conventional meat-based diets for dogs and cats, adding to the growing body of research examining plant-based nutrition for companion animals.

• A review published in Animals analyzed 31 studies examining the digestibility of vegan, vegetarian and plant-based pet diets for dogs and cats.
• Researchers found nutritionally complete plant-based diets and their key protein sources were generally well digested and broadly comparable with conventional meat-based diets.
• The authors called for further research on cats, kittens, senior pets and animals with health conditions to strengthen the available evidence.

Published in the journal Animals, the review assessed existing research on the digestibility of vegan, vegetarian and plant-based pet diets and ingredients. Of the 31 studies included, 22 focused on dogs, two on cats and seven examined both species.

Digestibility is an important measure because it indicates how effectively animals can break down food and absorb nutrients. While commercially available vegan pet foods are increasingly formulated to meet nutritional requirements, poor digestibility could still reduce the amount of nutrients available to the animal.

The review found that nutritionally sound vegan and vegetarian diets, together with their primary protein sources, were generally well digested by both dogs and cats.

Professor Andrew Knight, an animal welfare researcher affiliated with Griffith University's School of Environment and Science and author of the review, said the findings challenged a common assumption about plant-based pet nutrition.

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

The studies assessed a broad range of ingredients commonly used in plant-based pet foods, including wheat gluten, rice protein, soy-derived ingredients, peas, lentils, chickpeas, potato protein, quinoa and proteins produced through microbial fermentation.

Several studies also evaluated commercially available vegan dog foods containing ingredients such as peas, barley, oats, sunflower oil and lentils.

According to the review, digestibility remained high overall, even in cases where certain plant-derived nutrients were found to be less digestible than comparable animal-derived ingredients.

Knight said the findings should provide reassurance for owners considering plant-based diets for their pets, provided the products were nutritionally complete.

"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 choose products that clearly state they are nutritionally complete and are manufactured by companies able to demonstrate the nutritional rigor behind their formulations.

"I recommend pet caregivers check product labels.

"There should be a clear statement that the diet is nutritionally complete.

"It should come from a good pet food company that can provide information about the steps taken to ensure nutritional soundness, such as working with veterinary nutrition specialists."

While the review found encouraging evidence for both dogs and cats, the available research remains much more extensive for dogs. Only two of the 31 studies focused exclusively on cats, highlighting an area where further work is needed.

Knight said additional research should investigate the digestibility of vegan and vegetarian diets for cats in real-world settings, as well as among kittens, senior animals and pets with existing health conditions.

The review adds to a growing body of evidence examining alternative protein sources for companion animal nutrition. The authors concluded that carefully formulated plant-based diets can achieve digestibility comparable with conventional meat-based alternatives while meeting nutritional requirements.