A Canine Controversy: Dueling Reports on the Safety of Grain-Free Dog Foods

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An apparent uptick in a type of heart disease, biomedical research leading to dueling conclusions about safety, and a Food and Drug Administration (FDA) investigation, all against a backdrop of a corporate battle for market share and allegedly vested interests: Another story about Big Pharma?

No. This is a tale about dogs and dog foods, with the non-canine protagonists being dog owners, veterinary cardiologists and nutritionists, giant pet-food companies and small, independent dog-food makers, and the federal government. One might wonder if this increasingly heated contretemps is all bark and no bite, but it has alarmed many owners of America’s estimated 90 million dogs.

In July 2018, the FDA alerted pet owners and vets of a possible link between dogs eating foods containing peas, lentils, potatoes, and other legume seeds and canine dilated cardiomyopathy (DCM), a disease that results in an enlarged and weakened heart, leading to fatigue, difficulty breathing, coughing and fainting. Canine DCM is common among large, older dogs, and is often deadly. The agency issued a second alert in late June, and spokesperson Anne Norris said, “We will continue to convey our observations publicly as the investigation progresses.”

The alerts have elicited considerable criticism. Pet Business, an industry publication, called the FDA” alert speculation and “premature. . . given the mountain of evidence that we have to the contrary—in the form of the millions of dogs that have enjoyed great health while being fed these diets for years.”

“There is no proven association between any dietary strategy or specific diet and DCM,” Justin Shmalberg, a professor at the University of Florida College of Veterinary Medicine, declared. “The FDA is testing reported foods but has released limited information.” This is a very complicated scientific problem with the need for careful analysis, and we don’t yet have the level of analysis required to draw any conclusions or even to compare dogs with and without DCM, of similar breed and age, fed the same foods.” He also pointed out that “grain-free diets have been around long before it was a frequent appearance on the label.”

Nonetheless, many dog owners who had only heard the alerts in the media, without hearing the rejoinders of scientists like Shmalberg,  bombarded their vets and pet-food stores with questions. Could this be like the 2007 recall of Chinese pet food that had sickened and killed dogs and cats?

As a result—after years of rapid growth for “natural,” grain-free foods, which garnered a 46 percent share of the $8 billion U.S. dog-food market in 2018—sales declined slightly in the year ending September 21, according to Nielsen, a market-research firm. Many vets are recommending grain-free diets. Pet Age, a trade-industry publication, reported a shift toward longstanding, mass-market brands like Purina Dog Chow.    

One of the most prominent critics of grain-free diets is Lisa Freeman, a veterinary nutritionist at Tufts University’s Cummings School of Veterinary Medicine. “I am calling the suspected diets, ‘BEG diets’—boutique companies, exotic ingredients, or grain-free diets,” she wrote in a blog last November. She urged dog owners to “stick with a commercial pet food made by a well-established manufacturer that contains common ingredients including grains. Freeman ended with a warning, appealing to those whose dog “is a part of your family”: “I recommend you reconsider your dog’s diet until we know more.”

Daniel Schulof, a veterinary nutritionist and author of Dogs, Dog Food, and Dogma, strongly disagrees. “The recommendation that consumers avoid all grain-free pet foods is certain to harm wrongly implicated pet food manufacturers,” he said. “But I believe it’s also likely to have, on balance, a negative impact on the health of America’s dogs by driving consumers towards more carbohydrate-focused products.”

The FDA initially launched its investigation in the wake of reports by Joshua Stern, an associate professor of veterinary medicine, and resident Joanna Kaplan, both at the University of California at Davis, and Minneapolis veterinary cardiologist Janet Olson. In an “observational study” of 24 retrievers, Stern and Kaplan found that the cardiac health of dogs with DCM improved after going off a grain-free diet.

Ryan Yamka, another veterinary nutritionist and co-founder of Guardian Pet Food, criticized the UC Davis study. “They selected 40 retrievers they followed and eliminated 16, but didn’t say why,” he said, “and they never looked at genetic predispositions.”

The FDA did not examine a scientifically selected sample, but rather solicited disease reports from owners and vets, receiving about 500 in 2018 and early 2019. Golden retrievers were the most common breeds, although the agency noted “a reporting bias . . . due to breed-specific social media groups . . . [that] urged owners and vets to submit reports.”

A key anti-BEG argument is that grain-free foods are lower in taurine, an amino acid in meat, and taurine levels in retrievers on BEG diets were low. Taurine deficiency in a type of cat food was associated with DCM cases in the 1970s, but when manufacturers added taurine, DCM among cats all but disappeared.

However, the FDA also noted that taurine and other nutrient levels “were similar for both grain-free labeled and grain-containing products.” In addition, taurine levels were only measured in less than two-thirds of the FDA’s sample, and only 42 percent of these dogs had low taurine, according to Shmalberg.

Beyond the headlines suggesting that dog health foods could lead to heart disease, were other FDA caveats. “The prevalence of reports in dogs eating a grain-free diet might correlate also to market share,” the agency said. It also did not advise dietary changes.

Despite the somewhat circumspect nature of the FDA’s announcements, BEG defenders again were incensed when the agency issued its second alert,  which included names of the most frequently reported brands. Many cited the small sample sizes in the few studies and lack of solid evidence, and alleged that researchers had conflicts of interest. Susan Thixton, a self-described “pet-food safety” advocate,” criticized the agency’s list of brands and its failure to examine the quality of other ingredients in these foods. She also claimed that the FDA had provided advance information about its alert to the Pet Food Institute (PFI), the trade association representing most manufacturers.

Pet Age pointedly asked: ““Was there any scientific basis for the naming of these specific brands or was it simply based on frequency of the brand name being provided to the FDA. . . One has to wonder if this current DCM investigation is being conducted for the well-being of pets or if it is a well-planned ploy to attack independent retailers and small pet food manufacturers.”

The idea that there could be something more than science behind the critique of BEG diets was fueled by a commentary by Freeman, Stern, and others in the Journal of the American Veterinary Medical Association last December, two days after Freeman’s blog warning. The article only cited “preliminary results of a study” by Darcy Adin, a co-author at North Carolina State’s veterinary school, as well as “what we have heard” and “discussions” with colleagues. The journal noted that Freeman had received research support, consulted with, and given sponsored talks for the three largest dog-food companies—Nestle Purina, Hill’s Pet Nutrition, and Royal Canin (a division of Mars), and that Adin had been supported by Nestle Purina. Hill’s and Mars have also funded the UC Davis vet school.

This was enough to really get the fur flying. “This was a non-peer-reviewed, opinion-based article,” Yamka said. “People read it as factual, when it was more like an op-ed.”

Schulof, the founder and CEO of KetoNatural Pet Foods, called for the journal to retract the article and circulated a petition signed by signed by some 200 other animal nutritionists and cardiologists. “The FDA’s investigation was initiated by a group of American veterinarians with financial ties to three pet food companies,” he wrote in his “Optimal Dog” blog. “They primarily sell grain-based, kibble-style pet foods and have a profit incentive to depress sales of the grain-free products with which they compete.” According to Schulof, “Big Dog Food”  and the Morris Animal Foundation, a nonprofit started by the founder of Hill’s, gave more than $1 million to the UC Davis vet school between January 1, 2017 and July 2019. He said that the foundation gave $377,000 to Tufts, North Carolina State, and UC Davis in 2017. Freeman declined to comment.

Many corporations give money to universities, often designated to support research by individuals or teams, or for a specific study. Cummings School guidelines say that money may be given for “ground-breaking research.” Nor is it unusual for academics to consult for companies, nonprofits, government, and receive honoraria for talks and other engagements. Cummings says that it “has a progressive external consulting policy allowing for salary supplementation.”

With dog owners still concerned and confused, it is important to emphasize that no one has determined any causal connection between grain-free diets and DCM.

“We still don’t have a definitive answer,” Steven Rosenthal, a veterinary cardiologist with Maryland-based CVCA, which calls itself the world’s largest cardiac veterinary practice, and has been working with the FDA on its investigation. “We have seen the correlation between grain-free foods and DCM many times, and it’s concerning, but we can’t show cause.” Kaplan said that conclusions could not be drawn without larger sample sizes. And, buried in their December commentary, Freeman, Stern, and their colleagues, said that “a cause and effect relationship has not been proven,” and even “the apparent association may be spurious.”

Many factors, including “recipe formulation and your individual pet,” are likely involved with cases of DCM, according to the PFI and FDA. One respected institution that doesn’t have a dog in this fight is the Cornell College of Veterinary Medicine, which says: “It is likely that [DCM’s] etiology is multifactorial.”

Andrew L. Yarrow, a former New York Times reporter, U.S. history professor, and author of Man Out: Men on the Sidelines of American Life, writes frequently about business, economics, health care, and social trends.     

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