For the longest time, Ari Moore, 28, and her partner, wrestled with the idea of adopting cats. Committed vegans, the couple wasn't sure they could adequately square their ethical beliefs with a cat's nutritional needs.
But after research and conversations with other vegan cat owners, about four years ago, the pair decided to make the leap and adopted two homeless cats in their Brooklyn, N.Y., neighborhood.
"There's definitely a conflict in being a vegan that lives with a tiny carnivore. But we did it," Moore said. "We were convinced that we could do this in a healthy way. And we were convinced that we felt we couldn't say no to these animals. They needed a place to stay, and they worked their way into our hearts."
Now artists and activists (with one more feline in the family) in Ithaca, N.Y., Moore and her partner, Shira Golding, are part of a relatively small but deeply dedicated group of vegan pet owners who believe their cats' and dogs' diets should reflect their own beliefs about the treatment of animals and environmentally sustainable lifestyles.
Despite the anecdotal evidence the group has amassed that supports vegan pet diets, many veterinarians are reluctant to recommend the meatless option.
Tony Buffington, a professor of veterinary clinical sciences at Ohio State University, said that while it's technically possible to formulate healthy nonmeat diets for cats and dogs, it's complicated and something he urges pet owners to consider very seriously.
"Could there be vegan pets? Yes. Would I do it for my own animal? Never," he said.
If he were to help someone do it, he said he'd make sure that the animal was a healthy, neutered adult. He would strongly advise against vegan diets for young, rapidly growing animals and those that are pregnant.
Most of all, he said, "I would definitely look carefully into it."
Buffington also said that it's easier for dogs to adopt a vegan or less-restrictive vegetarian diet because their nutritional needs aren't as strict as those of cats.
Animal welfare advocates share his concerns.
"With humans, of course, we believe that whether or not to consume meat is a personal and private choice. With our pets, of course, we're deciding for them," said Mindy Bough, senior director for the American Society for the Prevention of Cruelty to Animals. "Someone has to look at their own personal views and work with a veterinarian to make sure nutritional deficiencies aren't occurring."
Dogs, she said, are mostly carnivores, but because their diets are more varied, they could get away with a vegetarian diet that also includes eggs and other meat products. Vegetarian diets can include eggs, milk and other animal products, whereas vegan diets cannot.
Although there are commercial vegan diets available, Bough said, "I am personally reluctant to recommend that as a first choice."
Cats, however, are another matter entirely, she said.
As obligate carnivores, cats have stringent dietary requirements and it's more challenging to make sure they get the nutrients they need, including the amino acid taurine, vitamin A, iron, calcium and vitamin B.
Although she's heard anecdotally of healthy vegan cats, she said she suspects that those cats may be supplementing their meat-free diets on their own.
"If they're not getting meat, they're probably going to try to hunt -- maybe for the mouse in the house or the bird in the yard," she said.
But pet owners like Moore and the manufacturers of vegan pet food maintain that most veterinarians don't have enough training in nutrition.
"Here's the reality: We've been doing this for 20 years. We have dogs over 19 years old in good health. We have cats over 22 years in good health," said Eric Weisman, CEO of Evolution Diet Pet Food Corp., a manufacturer of vegan cat and dog food.
Weisman said thousands of clients across the United States, including animal shelters, use his vegan pet foods with success.
Although it's true that the amino acid taurine and other proteins are necessary for cats and dogs, he said that synthetics can be added as substitutes.
"Our food is 100 percent complete according to state requirements," Weisman said. "We have all the proteins and all the fatty acids found in meat-based [foods] but without the cruelty and destruction of the environment."
Like many vegans, Moore said she chose her diet because she cares deeply about animals and wanted to "live [her] ethics." For her, extending veganism to her cats supports that choice and also helps reduce her environmental footprint.
"Just converting plants to animal protein is outrageously unsustainable. Anything we can do to reduce that makes life a little better for everybody," she said. Moore also said that she and her partner started a social network for vegan cat owners to help support others with similar beliefs.
Although he doesn't yet have the data to prove it, Jason Clay, a senior vice president for the World Wildlife Fund, said he suspects that, in its lifetime, the average cat in the United States and Europe has a larger environmental footprint than the average African.
Regardless, some think that there are other ways to live out one's beliefs and support the environment.
Christie Keith, the lead science writer for petconnection.com and a pet columnist for the San Francisco Chronicle, said pet owners concerned about their environmental impact can buy organic and sustainable pet foods or make home-made meals for their pets.
"You can get anything you want for pets now commercially or you can make it," she said.
Acquiring pets that naturally eat only plants is also another option.
"Overall, what I would say is when we turn wild animals into forage, I think it's an overall disrespectful thing to do. It's one thing to kill an animal for human consumption. It's another to grind it up and turn it into feed," said Paul Greenberg, an author of a forthcoming book on the future of fish who recently wrote a New York Times op-ed about the impact of the pet food industry on the world's fish stocks.
The use of wild fish in animal food causes significant problems for the world's food systems, he said.
But Greenberg does not support turning a carnivorous pet into a vegetarian pet.
"A carnivore is a carnivore," he said.
If anything, he favors looking down the food chain in considering a pet.
"A carnivore, be it a cat, a dog or a salmon, is a heavy burden for the environment and should not be brought under human care lightly," he wrote in his Times op-ed. "To me, a vegetarian substitute is seeming more and more appealing. Lately, I've had my eye on a guinea pig."