The impact of a vegan diet on the health of our pets is hotly debated among people on both sides.
But so far we have had no formal evaluation of the scientific evidence. In new research published today in Veterinary Sciences, we’ve compiled health outcomes from 16 studies on dogs and cats fed a vegan diet.
So, if you’re wondering if 2023 could be the year your best (pet) friend adopts a meat-free lifestyle, read on to learn about the benefits and risks, and what we still don’t know.
In recent years, people in many parts of the world have increasingly switched to vegetarian or vegan diets, driven by ethical concerns for animal welfare, sustainability, or based on perceived health benefits.
Pet owners may also want to feed their pets in line with these food choices. In fact, one study found that 35% of owners who weren’t feeding their pets vegan diets would consider them, but found too many barriers. The main concerns were nutritional adequacy, lack of veterinary support and the small number of vegan diets available on the market.
Traditionally, feeding a vegan diet to species that are predominantly carnivorous was thought to go against their “nature” and lead to serious health effects.
There has even been debate over whether feeding your pets a vegan diet is tantamount to animal cruelty. But what does science actually say?
Both dogs and cats are carnivores. Dogs are facultative carnivores, meaning they can digest plant material and survive without meat, but may not thrive.
Cats, on the other hand, are obligate carnivores. By definition, this means that their diet is over 70% meat and they cannot digest plant material.
The anatomy of the intestines of the dog and cat also clearly indicates their carnivorous lifestyle. Their teeth are designed to crush and grind meat and hold prey. Their intestines are also short and have a smaller capacity relative to their body size because, unlike herbivores, they do not need to ferment plant material to digest it.
The main problem with a vegan pet diet is that proteins from cereal grains or soybeans (the main proteins of plant origin) contain less essential amino acids, e.g. omega 3 fatty acids or taurine, and do not contain all the essential vitamins. These nutrients are essential for maintaining good heart, eye and liver function.
A number of studies have looked at the nutritional composition of vegan pet diets, and some of them have been found to be insufficient. Homemade vegan diets are particularly vulnerable to nutrient deficiencies, but some commercial diets may also fall short of the requirements set out by various animal nutrition guidelines.
But it’s all about vegan diets using an input-based approach – it’s based on predictions. If we really want to know the impact of these diets on health, we need to measure it in animals.
Evidence is missing
We conducted a type of study that is common in evidence-based practice, called a systematic review. These studies are a summary of all studies on a given topic; it is assessed for quality, which allows us to assess how confident we can be in making evidence-based recommendations.
Only 16 studies looked at the impact of a vegan diet on the health of dogs and cats. Cats were included in only six of them, despite being the species most at risk of nutrient deficiencies.
Many of these studies have used owners’ reports of health as measured outcomes, such as perceptions of health or body condition. They are likely subjective and may be prone to bias.
In the few studies that have measured health directly by examining animals or conducting laboratory tests, there has been little evidence of adverse effects of a vegan diet on the health of pets. Nutrient levels were generally within normal limits, no heart or eye abnormalities were detected, and body and coat condition was normal.
It should be noted, however, that these studies often included small numbers of animals, and the vegan diet was only fed to the animals for a few weeks – so the deficiency may not have had time to develop. In addition, study designs were often considered less reliable in evidence-based practice, for example without control groups being used as a comparison.
Owners’ perception of the health benefits of the diets was overwhelmingly positive. Benefits cited are reduced obesity, better breath odor and reduced skin irritation. The only drawback was the increased volume of droppings, which seemed tolerable to most owners.
Proceed with caution
Overall, it seems the jury is still out on whether feeding our carnivorous four-legged friends a vegan diet is actually safe.
What we can be sure of is that both the strong arguments for and against vegan pet feeding are potentially flawed and unsupported by evidence.
For now, owners who have committed to feeding their pets a vegan diet should exercise caution. Enjoy a complete and balanced commercial vegan diet formula and schedule regular health checkups with your veterinarian.
Alexandra Whittaker, Senior Lecturer, University of Adelaide; Adriana Domínguez-Oliva, animal welfare researcher, Universidad Autónoma Metropolitana (Mexico)and Daniel Mota-Rojas, a scientist
This article has been republished from The Conversation under a Creative Commons license. Read the original article.