Pet food trends are following their owners’ tastes. Even the meat-loving brands are marketing plants, the very ingredients they once sidelined-just not the plants the industry has historically relied on, like the high-protein soybean and corn-gluten meals.

Instead, Blue Buffalo Co. Ltd. offers a Chicken & Quinoa Ancient Grains recipe, for example, and a grain-free line from Nestle Purina Petcare Co.’s Beneful is now “accented with blueberries, pumpkin & spinach.” Honest Kitchen Inc., which uses only human-grade ingredients, has been selling its Chicken & Quinoa recipe since 2006 and now offers Beef & Chickpea, Duck & Sweet Potato, and Fish & Coconut blends as well.

Dogs aren’t wolves, after all. They’re omnivores, said Anna-Kate Shoveller, an assistant professor of animal biosciences at the University of Guelph, in Canada. “They do quite well on a vegetable-based or a lower-protein diet,” she said.

Shoveller researches nutrition in animals and has been conducting experiments and publishing on a newly controversial topic: feeding vegetables to domestic dogs. And despite recent documentaries and marketing trends, Labrador retrievers, cocker spaniels, and the rest of the nearly 70 million dogs living in homes in the U.S. do not need to be fed like wild beasts.

Consider the nearly $30 billion pet food market’s second —  and third-most-popular dog food brands: the relative newcomer Blue Buffalo, whose “farm-to-table inspired canine cuisine” features a portrait of a wolf on each bag of its Wilderness line, and Beneful, whose bags brag of “real” chicken, beef and salmon as “the #1 ingredient.” Together, the two brands sold more than $2.3 billion of dog chow last year. (Pedigree, Mars Inc.’s budget-friendly brand, was the top-selling dog food in the country in 2016, pulling in $1.6 billion, according to data from Euromonitor.)

Blue Buffalo has played the healthy-wolf card better than any other company, despite admitting in a lawsuit that its ingredients weren’t always as marketed. Founded in 2002, it commanded 7.5 percent of the U.S. dog food market last year, making it the fifth-largest seller in the country. That’s still small compared to Nestle Purina, No. 1 , at 23.5 percent-but down from 26.8 percent in 2011, according to Euromonitor.

If there’s a mythos around meat, plants come with their own presumptions. The industry’s pivot back to plants, if only certain ones, seems a bit silly to experts, at least from a nutritional point of view.

“If soy is bad, why is pea good?” said Ryan Yamka. Yamka is an animal nutritionist certified by the American College of Animal Sciences, as well as founder and independent consultant with Luna Science and Nutrition. “It all comes down to marketing,” he said.

Dogs aren’t doing the shopping

Pet food in the U.S. falls under a mix of federal and state regulations. Owners looking for assurance that a food meets their pets’ nutritional needs should look for the “Complete and Balanced” nutritional adequacy statement on the package. The statement is based on the dog or cat food nutrient profiles set by the Association of American Feed Control Officials and guarantees that the food is nutritionally balanced. Aafco has no enforcement power of its own, but most commercially available pet foods sold online comply with its profiles, no matter what ingredients are in them.

“Pets don’t need ingredients, they need nutrients,” said Mary Emma Young, the communications director at the Pet Food Institute, the industry’s trade group, repeating a popular refrain in the pet food world. They also need to be able to digest the nutrients-and to like the food, or they won’t eat it.

And while there is no shortage of consumers, bloggers and competitors questioning the safety and health of mass-produced pet foods, especially since the massive 2007 pet food recall that followed the poisoning of thousands of pets, the industry puts significant resources into research to meet the guidelines Aafco sets. Nestle Purina alone has more than 500 scientists on staff, including food scientists, nutritionists and veterinarians.

Yamka traces the ingredient obsession back to the recall, in which Chinese suppliers added contaminants to wheat gluten and rice protein concentrate to boost protein levels.

“Somehow soy and corn got rolled in,” he said, and companies began advertising “absence claims” to bring in concerned customers. “It made it easy to make wheat and grains the boogeyman.”

Add in the lifestyle trends emerging on the human side-gluten-free this, grain-free that-and pet food marketers found a willing consumer base.

“Nobody kept up with Blue Buffalo in marketing and advertising,” Yamka said. “You had a lot of market leaders back then trying to mimic that, but they couldn’t.”

Shoveller, the animal nutrition scientist, recently conducted a study that compared the palatability and digestibility of animal-based and vegetable-based diets. The results “suggest that dogs do not have an innate preference for animal or vegetable ingredient-based diets,” she and several other researchers wrote in a published study. On the digestibility side (to be published in a forthcoming paper), her team examined the feces of the test subjects, eight adult beagles, to determine how much of the foods’ mineral content had been digested.

“All dogs had great stools on both diets,” she said.

Even though the study was relatively small and there is more research to be done, Shoveller said, “if there is a vegetable-based formula that meets the Aafco targets, it would be entirely safe to feed it to your dog.”

So pet food companies can formulate nutritionally sound diets from non-sexy plant ingredients-corn and soy would suffice. Fancy grains are just better attention grabbers.

“The reality is that the dogs and cats don’t get to push the grocery carts and pay for the food,” said Daniel Smith, vice president of research and development at Nestle Purina Petcare Ptc. “We have to be sensitive to what the owners choices are and deliver what the dog or cat enjoys.”

Oh yes, cats

As “obligate carnivores,” cats need certain amino acids available only in meat. They’re also pickier eaters.

“We have tried to do vegetable- or plant-based proteins and supplement them with some synthetic amino acids,” Smith said. “But then we run into another problem: Cats won’t eat it. Dogs are less judicious.”

Saving the world … with pet food?

Sustainability concerns are often cited as one reason so many people are moving to more plant-based diets, and it’s echoed in the pet food industry. But while a chickpea burger undoubtedly has a smaller carbon footprint than its beef counterpart, it’s not as simple on the pet food side. The meat that goes into pet food is often animal parts Americans don’t want to eat, even if they’re perfectly edible and consumed in other cultures. When they land in kibble, they don’t land in a landfill.

“We’re not competing with the human side,” Smith said. “We’re taking away a stream that’s going to go to waste.”

With plants, there often is no byproduct; the ingredient is your dinner. So a plant-based pet food might be less sustainable than an animal version.

Consider the ingredients used by Honest Kitchen. The poultry meat, which comes from such producers as Whole Foods Market Inc. supplier Diestel Turkey Ranch, is made up of the muscle meat left on the carcass after the pieces-the breasts, thighs and so forth-have been stripped, packaged and sold as parts. But the non-GMO-certified quinoa grown by micro-farmers in Bolivia is “the same quinoa that would be grown for human food,” said founder Lucy Postins. To feed both pets and humans, those Bolivian farmers would need to grow more, using more resources.

There is plant waste that could be diverted into pet food, Smith noted, such as stalks from broccoli that humans tend to toss in the garbage. But it’s not always available, so manufacturers have to dip into the human supply.

“If we can’t get to the complementary side, it gets competitive,” he said. “Is the consumer willing to pay the amount that it would cost to get that ingredient?”

That helps explain why a four-pound box of Honest Kitchen’s dehydrated Chicken & Quinoa blend, which with water added makes 16 pounds, costs $43.99. A 17-pound bag of Pedigree costs $16.09.

Plus, quinoa isn’t available in large supplies, said Fred van de Velde, the protein functionality group leader at NIZO, a private research and development company focused on food technology, so “it won’t be a golden ingredient.” Instead, he’s eyeing aqueous crops such as algae, which can grow year-round in areas inhospitable to other crops. Don’t expect it to be a headliner-it’s not a super trendy human food. (Yet.)

Other factors come into play in the sustainability equation: the location of the ingredient, the carbon used to ship it, the energy needed to process it.

Is a quinoa-blended dog food more sustainable? That depends. Healthier? Probably not. Trendier? For sure. More expensive? Almost certainly.