A study published in Nature’s Scientific Reports was not meant to find relationships among chemical compounds and dog health, particularly instances of canine dilated cardiomyopathy, the author told Petfood Industry.
The study, led by Tufts University professor Lisa Freeman, DVM, PhD, found chemical differences between those dog foods associated with DCM and other commercial dog foods. The brands were associated with DCM by a U.S. Food and Drug Administration investigation that started in 2018.
However, business-to-consumer news media outlets have covered the research as if it found a causal relationship among certain ingredients, especially peas, and canine dilated cardiomyopathy.
“A new study from Tufts links certain dry dog foods to deadly canine heart disease, and researchers are eyeing peas as a potentially dangerous ingredient for pooches,” the Boston Herald reported, for example.
“More specifically, the research sponsored by the United States Food and Drug Administration (FDA) suggests a common vegetable—peas—could lead to the potential problem,” reported the Smithsonian.
Research on chemicals in pet foods associated with DCM
Freeman termed the dog foods mentioned in the FDA announcements as 3P/FDA diets.
“We identified 88 biochemical compounds that were higher and 23 compounds that were lower in 3P/FDA diets,” Freeman said. “Machine-learning analysis identified the top 30 compounds that distinguished the two diet groups with 100% predictive accuracy. Four diet ingredients distinguished the two diet groups (peas, lentils, chicken/turkey, and rice). Of these ingredients, peas showed the greatest association with higher concentrations of compounds in DCM-associated diets.”
The study was funded in part by Nestlé Purina PetCare, the Barkley Fund and the U.S. Department of Agriculture.
“This study used an approach derived from metabolomics—which measures small molecules that can identify biomarkers of disease or diet—to compare biochemical compounds in dog foods,” she wrote. “The study’s primary objective was to use this ‘foodomics’ approach to identify biochemical compounds that differ between commercial dog foods that have been associated with canine DCM compared to more traditional commercial dog foods.”
In his Petfood Industry blog, Ryan Yamka, PhD, discussed the methodology used in Freeman’s study: DCM and grain-free pet foods: 3 strikes and you’re out!
Freeman acknowledged limitations of her study.
“Our foodomics analysis does not account for any changes in diet formulation that might have occurred after the time of analysis,” she said. “One next step in our research is to measure compounds by metabolomic analysis in dogs with DCM and to compare results between the diets and the dogs.”
FDA investigation into DCM and grain-free dog food
In July 2018, the U.S. Food and Drug Administration’s (FDA) publicly announced the agency’s investigation into correlations among certain dog foods and DCM. Federal authorities examined reports of DCM in dogs eating certain diets labeled as grain-free, particularly those containing peas, lentils, other legume seeds, or potatoes as main ingredients, which were more common in diets labeled as grain-free. A year later, the agency released data from their investigation that stated 93% of the 524 reported cases of DCM, involved dog foods made with peas and/or lentils, while 90% of the afflicted dogs had eaten diets labeled as grain-free. The FDA named 16 brands most frequently eaten by dogs involved in official reports of DCM. Sales of grain-free dog food in general, and those named brands especially, fell following FDA’s announcements.
Although the FDA investigation caused upheaval in pet food markets, scientists and others involved in the industry have pointed out the lack of direct evidence connecting those grain-free dog foods to DCM, since the first FDA announcement. Likewise, some have criticized the FDA for going public with the investigation before solid evidence existed, especially considering the negative economic consequences for dog food brands.
Canine dilated cardiomyopathy heart disease
DCM affects dogs’ heart muscles. The disease results in an enlarged heart. As the heart and its chambers become dilated, pumping becomes more difficult and heart valves may leak, leading to a buildup of fluids in the chest and abdomen. DCM often results in congestive heart failure. Heart function may improve in cases that are not linked to genetics with appropriate veterinary treatment and dietary modification, if caught early. Breeds that are typically more frequently affected by DCM include large and giant breed dogs, such as Great Danes, Boxers, Newfoundlands, Irish Wolfhounds, Saint Bernards and Doberman Pinschers. It is less common in small and medium breed dogs, except American and English Cocker Spaniels. Cases reported to the FDA included Golden and Labrador Retrievers, Whippets, a Shih Tzu, a Bulldog and Miniature Schnauzers, as well as mixed breeds.
