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

Tufts University researchers analyzed compounds found in dog foods associated with canine dilated cardiomyopathy.

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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