With more folks eschewing meat and adopting a plant-based diet for health reasons, many are opting to make that choice for their pets. According to a study published in PLOS One, over one third of pet owners in English-speaking countries, the United States included, have considered putting their pets on plant-based diets. However, veterinary nutritionists warn that while dogs, who are omnivores, may be able to eke by without meat, cats are definitely carnivores and need to eat meat to derive essential nutrition for their health.

"Removing meat from a cat's diet can have fatal consequences," Dr. Chris Greenwell, a vet at RSPCA Sydney Veterinary Hospital in New South Wales told The Daily Mail recently. "When these ingredients are depleted over time there are many negative health impacts."

The expert states that cats need an amino acid called taurine, which is essential to their diet. They also require arginine, arachidonic avid, and vitamins A and B. These nutrients are derived from a meat-based diet.

However, if you want a vegetarian pet, dogs are more promising, say experts. That being said, lots of thought and preparation need to go into what you feed your dog, says Cailin Heinze, VMD, MS, a veterinary nutritional expert at Cummings Veterinary Medical Center at Tuft's University.

"Vegan diets or home-prepared diets in general can cause numerous health issues if not designed by someone with considerable dog nutrition expertise," she says. "Most dogs can do quite well on a carefully designed vegan diet that meets all their nutritional needs. As a veterinary nutritionist, I use meat-free diets quite a bit to help manage various health concerns."

The risks of feeding dogs or cats vegetarian or vegan diets include:

• Inadequate total protein — less than 25 grams per 1,000 calories.
• Insufficient nutrients. Dogs and cats cannot make vitamin D in their skin so it needs to be in their diet. And it must be in the form of D3, not D2, which comes from plant-based sources. D3 comes from animal sources.
• Taurine. Dogs can make taurine if they have the right protein-based building blocks, but cats cannot. This amino acid must be present in a feline diet.
• Deficiency in vitamins and minerals such as B vitamins, calcium, phosphorus, and iron that are obtained ideally through meat or other animal products, according to WebMD.

If you do decide to feed your dog or cat a vegetarian diet, consider commercially approved formulas that meet the requirements for the Association of American Feed Control Officials (AAFCO). Schedule regular wellness exams, including blood work, at least twice a year for pets eating a vegetarian diet.

"Dog owners who insist upon feeding a vegetarian diet and especially a vegan diet should seek an experienced veterinary nutritionist to discuss their dog's needs and develop a diet plan that minimizes the risks," says Heinze. "There is a lot of room for error, and these diets probably are not as appropriate as diets that contains at least some animal protein." That's why adding eggs, for example, to the dog's diet is less worrisome than giving it strict vegan fare with no dairy or eggs.

Better still, says Lew Olson, PhD, author of "Raw and Natural Nutrition for Dogs," who was a psychotherapist before he changed careers, get a more appropriate pet if you insist on feeding plant-based foods.

"People do this to make themselves happy," he says. "It's not about the animal. When people tell me they want to feed a vegan diet, I say 'get a goat, get a rabbit.'"