After receiving more than 1,300 reports of dilated cardiomyopathy in dogs, the agency announced it couldn't establish a causal connection. Questions about the investigation's handling persist.
In July 2018, the U.S. Food and Drug Administration launched an investigation into a disturbing pattern: dogs were developing a potentially fatal heart condition called dilated cardiomyopathy, and many shared one thing in common. They were eating grain-free diets high in peas, lentils, and potatoes.
Four and a half years later, the agency quietly ended routine updates on the investigation, announcing on December 23, 2022, that it had "insufficient data to establish a causal relationship" between the diets and DCM. The timing (the Friday before Christmas) struck many observers as an attempt to bury unfavorable news.
A disease that shouldn't have been there
Dilated cardiomyopathy causes a dog's heart to enlarge and weaken, making it unable to pump blood effectively. The condition often leads to congestive heart failure and can cause sudden death without warning symptoms. While DCM is typically genetic and affects large breeds like Dobermans and Great Danes, veterinary cardiologists began noticing something unusual in 2017 and early 2018.
Golden Retrievers, mixed breeds, and other dogs without genetic predisposition were showing up with DCM. When veterinarians examined their diets, a pattern emerged: many were eating "grain-free" foods that contained high proportions of peas, lentils, chickpeas, and potatoes as main ingredients.
Between January 2018 and April 2019 alone, the FDA received reports of 553 dogs with DCM, compared to previous years when reports ranged from zero to three annually. The agency had actually received sporadic reports as early as 2014 and 2015, but the 2018 surge triggered the formal investigation.
The investigation that sparked industry upheaval
When the FDA publicly announced its investigation in July 2018, it sent shockwaves through the pet food industry. Grain-free diets had become enormously popular, representing approximately 43 percent of dry dog food sales by 2019, reaching $5.4 billion annually.
In June 2019, the FDA took the unprecedented step of naming 16 dog food brands most frequently associated with DCM reports. More than 90 percent of products were grain-free, and 93 percent contained peas and/or lentils as main ingredients. Sales of the named brands plummeted.
By November 2022, the agency had received 1,382 total DCM reports in dogs. Research showed that affected dogs often improved when switched to grain-inclusive diets, a finding that suggested diet played a role in some cases. Dogs that changed their diets lived an average of 465 days after diagnosis, compared to 263 days for those that didn't switch.
Conflicts of interest raise questions
A six-month investigation by 100Reporters revealed that veterinarians who initially prompted the FDA to examine the diet connection had financial ties to leading sellers of grain-inclusive pet foods, including Hill's Pet Nutrition, Nestlé Purina, and Mars Petcare.
FDA records obtained through Freedom of Information Act requests showed that some veterinarians were instructed to report only DCM cases where dogs ate "boutique, exotic ingredient, or grain-free" diets, potentially skewing the data from the start. The three veterinary cardiologists who collaborated most closely with the FDA (Dr. Lisa Freeman of Tufts University, Dr. Joshua Stern of UC Davis, and Dr. Darcy Adin of the University of Florida) all had received funding from major grain-inclusive pet food manufacturers.
"It's hard to find a veterinary nutritionist that hasn't done research for pet food companies," Dr. Stern acknowledged in an interview with 100Reporters.
The investigation also found that the pulse industry (suppliers of peas, lentils, and other legume ingredients used in grain-free foods) applied pressure on the FDA. The USA Dry Pea & Lentil Council's 2019 annual report claimed the organization "convinced the FDA to clarify their language about their concerns and minimize the damage to the industry."
The quiet exit
The FDA's December 2022 announcement was not issued as a press release. Instead, a brief paragraph was quietly added to a three-year-old webpage. The agency stated it would not release further updates "until there is meaningful new scientific information to share."
Critics argue the investigation began with premature public announcements that harmed grain-free brands, then ended without closure for pet owners who lost dogs to the disease.
"Where they erred, in my opinion, was in rushing to judgment and action by making a major announcement soon after, rather than first doing some investigation," wrote Pet Food Industry columnist Debbie Phillips-Donaldson. "Really, is anyone satisfied or believing this is a completely closed matter?"
What's next
Despite the FDA's withdrawal, research continues. Veterinary cardiologists still report seeing dogs with diet-associated DCM, particularly in regions where grain-free diets remain popular. Recent studies from Tufts University and other institutions continue to find associations between high-pulse diets and cardiac changes in dogs.
A $2.6 billion lawsuit filed in February 2024 against Hill's Pet Nutrition and affiliated veterinary researchers alleges the FDA investigation was "fraudulently induced" by researchers with financial conflicts of interest, causing economic harm to grain-free pet food manufacturers.
For dog owners, the message remains frustratingly unclear. The FDA never formally recommended against grain-free diets, yet never cleared them either. Veterinary nutritionists continue to advise caution about diets with peas, lentils, or potatoes high in the ingredient list, while acknowledging the exact mechanism linking these ingredients to heart disease remains unknown.
The 77 million dogs in American households continue eating their kibble. Most will never develop DCM. But for the families of dogs who did, and the industry left to pick up the pieces, the FDA's quiet exit offers little satisfaction.
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