**FDA’s Work on Potential Causes of Non-Hereditary DCM in Dogs

In September 2020, FDA joined scientific experts from academia, industry, and veterinary medicine in a scientific forum hosted by Kansas State UniversityExternal Link Disclaimer to examine the potential causes of non-hereditary dilated cardiomyopathy (DCM) in dogs. The event was a forum where scientists with research into DCM could share information, collaborate, and discuss many different – and even conflicting – theories on the condition. FDA; the veterinary community, especially veterinary nutritionists and veterinary cardiologists and other specialists; industry and academia, continue to examine this issue to help determine what factors may be contributing to the heart conditions observed and reported to FDA.

Because every dog is unique and has their own nutritional needs, your veterinarian is in the best position to advise you on how to best feed your dog. Please consult your veterinarian to discuss before making a change in your dog’s diet. We encourage veterinarians to review the KSU proceedingsExternal Link Disclaimer to learn more about the current research on this issue.

We recognize that you may have questions. Below we have compiled answers to address some of the frequently asked questions raised by pet owners and veterinarians. These may be updated as we learn more.

1. What is canine dilated cardiomyopathy (DCM) and how does non-hereditary DCM differ from the genetic form?
DCM is a disease of a dog’s heart muscle and results in an enlarged heart. As the heart and its chambers become dilated, it becomes harder for the heart to pump, and heart valves may leak, which can lead to a buildup of fluids in the chest and abdomen (congestive heart failure).

Historically, DCM has been primarily linked to a genetic predisposition in certain breeds, but emerging science appears to indicate that non-hereditary forms of DCM occur in dogs as a complex medical condition that may be affected by the interplay of multiple factors such as genetics, underlying medical conditions, and diet. Aspects of diet that may interact with genetics and underlying medical conditions may include nutritional makeup of the ingredients and how dogs digest them, ingredient sourcing, processing, formulation, and/or feeding practices.

Reports from veterinary cardiologists demonstrate some good results in improving heart function in non-hereditary DCM cases, unlike genetic forms of DCM, with appropriate veterinary treatment and dietary modification, when caught early in the progression of the disease.

2. Why is FDA focused on potential dietary causes of non-hereditary DCM?
While non-hereditary DCM appears to be caused by a confluence of multiple factors, FDA is a regulatory agency and has regulatory authority over animal food, including pet food, thus the reason for the agency’s focus on diet as a potential contributor. There is no public health agency that tracks animal health in the same way that the Centers for Disease Control and Prevention tracks human health, therefore FDA has called on the veterinary and academic communities, as well as industry, to contribute research on various aspects of non-hereditary DCM. Many representatives from these sectors participated in the recent KSU scientific forum and several agreed to publicly share their abstracts and/or presentations.

3. What is FDA doing to better understand non-hereditary DCM cases?
Our veterinarians, animal nutritionists, epidemiologists and pathologists have been working with veterinary cardiologists and nutritionists from academia, industry and private practice to better understand the clinical presentation of the cases and potential ties to diet, such as bioavailability of critical nutrients and how well a dog digests these nutrients. FDA scientists also presentedExternal Link Disclaimer at the KSU symposium on a subset of dogs that had fully or partially recovered from DCM with diet change and veterinary care.

4. What additional information would help further understanding of non-hereditary DCM?
FDA is encouraged by the response of veterinary cardiologists, veterinary nutritionists, academia and industry in delving into this issue and we encourage other scientists to take part. As we look further into the role that diet may play in these cases, we hope to explore additional avenues of inquiry such as formulation, nutrient bioavailability, ingredient sourcing, and diet processing to determine if there are any common factors. We have asked pet food manufacturers to share diet formulation information, which could substantially benefit our understanding of the role of diet in the development of non-hereditary DCM. Formulation data shared with the FDA will be kept confidential.

5. How many cases have been reported to the FDA?
Between January 1, 2014 and July 31, 2020, the FDA received more than 1100 case reports of diagnosed dilated cardiomyopathy in dogs. The majority of these cases were reported immediately after FDA provided public updates. Some of these cases involved more than one animal from the same household. In the reported cases, more than 280 of those dogs were reported to have died. Of the approximately 20 cat reports, there were approximately 13 cat deaths. The agency received additional reports of other types of cardiac disease in dogs, however, these reports did not meet our case definition requirement of a confirmed DCM diagnosis.

6. Do the diets associated with cases of non-hereditary DCM appear to have any commonalities?
Most of the diets associated with the reports of non-hereditary DCM have legume seed ingredients, also called “pulses” (e.g., peas, lentils, etc.), high in their ingredient lists (although soy is a legume, we did not see a signal associated with this ingredient). These include both “grain-free” and grain-containing formulations. Legumes, including pulse ingredients, have been used in pet foods for many years, with no evidence to indicate they are inherently dangerous, but analysis of data reported to CVM indicates that pulse ingredients are used in many “grain-free” diets in greater proportion than in most grain-containing formulas. FDA has asked pet food manufacturers to provide diet formulations so we can further understand the proportions of ingredients in commercially-available diets and possible relationships with non-hereditary DCM.

The FDA does not know the specific connection between these diets and cases of non-hereditary DCM and is continuing to explore the role of genetics, underlying medical conditions, and/or other factors.

7. Is FDA planning to continue naming the brands most associated with cases?
No, we are not planning to update the commonly reported brands, as we are aware that several pet food companies have adjusted diet formulations since our initial announcements about DCM. We have asked pet food manufacturers to share diet formulation information, which could substantially benefit our understanding of the role of diet in these cases. We continue to encourage pet owners to discuss their animals' diets with their veterinarians.

8. Is this an issue with only grain-free diets or diets containing legumes or pulses?
No. FDA has received reports of non-hereditary DCM associated with both grain-free and grain-containing diets. Most of the diets associated with reports of non-hereditary DCM have non-soy legumes and pulses (e.g., peas, lentils, etc.) high in their ingredient lists. However, it is important to note that legumes and pulses have been used in pet foods for many years, with no evidence to indicate they are inherently dangerous. CVM’s data show that pulse ingredients are likely used in many “grain-free” diets in greater proportion than in most grain-containing formulas.

9. As a regulatory agency, has FDA requested any recalls of pet foods associated with non-hereditary DCM?
FDA has no definitive information indicating that the diets are inherently unsafe and need to be removed from the market, but we are continuing to work with stakeholders in assessing how the diets may interact with other factors that may be impacting non-hereditary DCM. We encourage pet owners to work with their veterinarians, who may consult with a board-certified veterinary nutritionist, prior to making diet changes. We also encourage veterinarians to review the proceedings of the KSU symposium in order to learn more about non-hereditary DCM. FDA continues to pursue scientific understanding of non-hereditary DCM and welcomes additional contributions from other scientists.

10. How long will it take to pinpoint the cause(s) of non-hereditary DCM?
We see this as an ongoing, collaborative scientific venture, of which FDA has just one piece as the regulator of animal food and reviewer of adverse event reports received as part of the pet food early warning and surveillance system. The scientific community continues to assess the available information and fill data gaps to determine what factors may contribute to the development of non-hereditary DCM. We look forward to continuing to engage with scientists as opportunities arise. We will also provide additional updates to notify the public if or when substantive scientific information comes to light.

We have an update:



New Study Adds Fuel to DCM and Grain-free Dog Food Controversy

DCM and grain-free foods—here we go again.

A study first published in the Journal of Veterinary Internal Medicine in December 2020 using medical records dated from 2014-2018 seems to demonstrate that dogs with dilated cardiomyopathy (DCM) that were consuming “nontraditional dog foods"—namely, grain-free diets—were more likely to show signs of significant improvement in cardiac function if put back on “traditional” diets, along with being treated with heart medications.

So, it’s not an outright indictment on grain-free dog foods, but certainly not an endorsement.

The study follows the U.S. Food & Drug Administration’s (FDA) investigation of a suspected correlation between grain-free dog foods and instances of canine DCM, and adds a new wrinkle to what has become a quagmire for pet specialty retailers and pet food manufacturers who are trying to do right by their customers.

Since the FDA has raised the question of a potential link between DCM and grain-free foods—particularly diets formulated with legumes or pulses to replace the grains—others in the scientific community are also taking a closer look and adding their findings to a growing well of research on the topic.

However, it was only a few months ago that Pet Product News (PPN) reported that an FDA official acknowledged during a virtual scientific forum hosted by Kansas State University (KSU) in late September that there is no clear evidence indicating that grain-free foods with pulse ingredients are inherently dangerous for dogs and conceded that the “complex scientific messaging” was often lost in translation in the media.

And back in July, research published in the Journal of Animal Science—backed by veterinarians, veterinary cardiologists and animal nutritionists from BSM Partners, a pet care research and consulting firm—concluded that there is no definitive link between DCM and grain-free diets, a conclusion that we said came as no surprise to many industry insiders.

The news gave us perhaps a little hope—maybe false—that any concerns about the health impacts of grain-free diets would soon fall to the wayside.

So what impact will this newly published study have on anyone’s understanding of the issue?

It’s hard to say, and it’s probably most accurate to portend that our understanding of any potential link—or the absence thereof—will continue to evolve as more independent researchers reveal new findings and as the FDA continues its investigation. The one thing everyone seems to be in agreement on is that more research is still needed.

In the meantime, this new study may amplify concerns that, at the very least, pet foods that contain typical grains and not pulses—referred to by the researchers as traditional foods—may be better suited for dogs that have DCM or that may be predisposed to the condition than grain-free pet foods containing pulses, or nontraditional foods.

The study was funded by the Barkley Fund—a funding arm of Tuft University’s Cummings School of Veterinary Medicine, which aims to improve the care of animals with heart disease by supporting clinical investigations, teaching and learning—and was conducted by researchers from the department of clinical sciences at Cummings that included: Kimberly J. Freid, Lisa M. Freeman, John E. Rush, Suzanne M. Cunningham, Megan S. Davis, Emily T. Karlin and Vicky K. Yang.

The study reviewed the medical records of dogs diagnosed with DCM between Jan. 1, 2014, and Sept. 30, 2018, and grouped dogs into “traditional” or “nontraditional” diet categories and whether or not diet was changed after diagnosis. While the researchers did conclude that dogs with DCM that had been eating nontraditional diets improved at a greater rate when put back on traditional formulas, they also conceded that more research was needed to examine a possible link between the heart condition and diet.

Also, in their declaration of conflict of interest, two of the researchers—Freid and Rush—disclosed connections to pet food companies such as Hill’s Pet Nutrition, Nestlé Purina, Royal Canin and Mars—whether it was in the form of sponsored lectures or some sort of professional services.

Again, it’s hard to weigh the impact of this study yet, and it may be even tougher for some in the pet industry to know how to advise confused pet owners on how to feed their pets. So in essence, nothing much has changed—pet retailers and manufacturers need to stay abreast of the new research as it develops, and not necessarily make any knee-jerk responses as we all await the definitive answers we seek.

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An update:

New 'piece of the puzzle': Why some dog foods may be linked to deadly heart disease

A new clue has been found that might help solve the puzzle of how certain dog foods may lead to a deadly form of canine heart disease, a new study suggests.

Researchers compared dog foods that the Food and Drug Administration has associated with canine dilated cardiomyopathy and traditional dog foods, looking at the quantities of more than 800 compounds. They discovered some that might be related to DCM. Right now, peas are at the top of the list of ingredients associated with the compounds, according to the report published Thursday in Scientific Reports.

Peas are included in many grain-free dog foods — which may increase or add pulses, such as peas or lentils, and potatoes to their formulations to replace the grain — and in some traditional dog foods, according to the FDA.

“I see this as a piece of the puzzle,” said a researcher, Dr. Lisa Freeman, a professor and board-certified veterinary nutritionist at the Cummings School of Veterinary Medicine at Tufts University. “This research helps us narrow down the targets to look at so we can focus on the most likely causes and get to an answer more quickly and prevent other dogs from being affected.”

Canine dilated cardiomyopathy, or DCM, is a severe disease of the heart muscle that can develop in dogs and humans, causing the heart to grow bigger and its contractions weaker. Ultimately, the disease can end in heart failure and death. Some breeds of large dogs are genetically susceptible to DCM, including Great Danes, German shepherds and Doberman pinschers, according to VCA Animal Hospitals.

Freeman and her colleagues used an approach called foodomics to compare the biochemical compounds that differ between traditional dog foods and those that might be linked to DCM.

The researchers compared 830 compounds in nine traditional dog foods to nine that have been associated with DCM. They dubbed the suspect products 3P/FDA, because of the three ingredients — pulses, potatoes and sweet potatoes — that are in the dog foods’ top 20 components.

Of the 122 compounds that were significantly higher in the 3P/FDA foods than in traditional foods, 24 were amino acid-related and 20 were plant compounds. Among the 27 compounds that were lowest in the suspect dog foods compared to traditional foods were seven B vitamins.

A further analysis, using machine learning, narrowed the number of suspect compounds to 30. The ingredient that was most strongly associated with those compounds was peas, which have been a focus of the FDA's investigation. Because some of the ingredients have been found in dog foods that haven’t been linked to the heart condition, the issue may be how much of them is used, according to the FDA.

However, Freeman isn’t ready to steer dog owners away from all foods containing peas.

“Until we know the exact cause, we want to be cautious of all the ingredients the FDA is investigating,” she said. “Peas might be a good clue as to where we can be looking. As one more piece of the puzzle, this doesn’t give us the final answer, unfortunately. But it gives us things to follow up on.”

The new findings may be a “piece of the puzzle,” but it’s a very complicated puzzle, said Dr. Joseph Wakshlag, a professor of nutrition at the Cornell University College of Veterinary Medicine.

The condition may end up being a combination of susceptibility genes and certain foods, said Wakshlag. “Maybe if you have subpar nutrients and a particular genetic type, you might get the perfect storm,” he said.

Since the FDA began warning dog owners in 2014 that heart failure in their dogs might be associated with some types of food, more than 1,100 cases of diagnosed DCM have been reported to the agency. At least 280 of the dogs died.

Ultimately, the best way to stay out of trouble with dog foods is to stick with the ones that have been around for decades and haven’t been implicated in diseases like DCM, said Wakshlag, who has no ties to dog food companies.

The FDA hasn’t recommended a recall related to the heart disease or declared any specific pet food products unsafe. Dog owners who are concerned about a pet's food can submit safety reports to the FDA at the Safety Reporting Portal.

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