For nearly a decade, grain-free dog food has been linked to canine dilated cardiomyopathy (DCM). Headlines, social media posts, and well-meaning advice have led many dog owners to believe that grain-free diets are dangerous.
But when you look closely at the science, the story is far more nuanced.
Current evidence does not show a proven cause-and-effect relationship between grain-free diets and DCM. Research instead points to a complex, multifactorial disease influenced by genetics, overall diet formulation, and possibly certain ingredients—particularly very high legume inclusion—rather than the simple absence of grains (Freeman, Stern, Fries, Adin, & Rush, 2018; Kaplan et al., 2024; Caro-Vadillo et al., 2023).
How the concern started
Between 2014 and 2018, veterinary cardiologists noticed clusters of DCM cases in dogs eating certain “boutique, exotic, grain-free” (BEG) diets (Freeman et al., 2018; Adin, DeFrancesco, Keene, et al., 2019). Many of these foods relied heavily on peas, lentils, and other legumes.
Because a large proportion of reported cases involved grain-free diets, a hypothesised association was publicised before a biological mechanism or proof of causation had been established (Freeman et al., 2018).
These early reports had limitations. They were retrospective, often lacked complete diet histories, and frequently involved breeds genetically predisposed to DCM.
Despite these weaknesses, the idea that “grain-free causes heart disease” spread quickly and widely (Freeman et al., 2018; Adin et al., 2019).
What the research actually shows
As more data became available, the narrative shifted.
A large peer-reviewed review highlighted that there is no definitive relationship between grain-free or legume-rich diets and DCM and emphasised that early case reports contained confounding factors, preventing causal conclusions (Freeman et al., 2018).
Population-level studies also challenge a simple “grain-free = DCM” link. Caro-Vadillo et al. (2023) compared DCM diagnoses from 2000 to 2019 with the surge in grain-free dog food sales over the same period. Despite the growth in grain-free diets, the proportion of dogs diagnosed with DCM did not increase, indicating no correlation at the population level.
DCM is not a simple disease
DCM is widely recognized as a multifactorial condition. Genetics remain the primary risk factor, particularly in breeds such as Doberman, Boxers, and Great Danes (Kittleson & Kienle,1998).
Other contributors can include:
• Specific nutrient deficiencies (such as taurine or carnitine)
• Myocarditis
• Chronic tachycardia
• Endocrine disorders like hypothyroidism (Freeman et al., 2018; Kaplan et al., 2024)
When diet plays a role, it is typically due to nutritional imbalance or formulation issues, not the presence or absence of grains. Importantly, diet-associated DCM has been reported with both grain-free and grain-containing foods, and many dogs improve after diet correction and treatment (Ontiveros et al., 2020).
And it’s worth pointing out that a main nutritional deficiency associated with DCM aren’t found in grain. Primary sources for both taurine and carnitine are meat.
What controlled studies tell us
Controlled, prospective studies provide clarity.
Kaplan et al. (2024) conducted an 18-month randomised, double-blind study of healthy adult dogs fed complete and balanced diets with different carbohydrate sources, including grain-free and grain-inclusive formulations. Over the study period, dogs in all groups maintained normal heart structure and function.
This supports the conclusion that, in healthy dogs, properly formulated grain-free diets are not inherently harmful to cardiac health (Kaplan et al., 2024).
Why “grain-free causes DCM” isn’t supported by science
When all available evidence is considered together:
• Early reports showed association, not causation (Freeman et al., 2018; Adin et al., 2019)
• Large reviews found no definitive link (Freeman et al., 2018)
• Population studies showed no increase in DCM despite rising grain-free use (Caro-Vadillo et al., 2023)
• Controlled studies show normal cardiac function on balanced grain-free diets (Kaplan et al., 2024)
The science simply does not support the claim that grain-free diets are inherently dangerous and yet this is still being touted by vets!
References
Adin, D. B., DeFrancesco, T. C., Keene, B. W., et al. (2019). Echocardiographic phenotype of canine dilated cardiomyopathy differs based on diet type. Journal of Veterinary Cardiology, 21, 1–9. https://doi.org/10.1016/j.jvc.2018.11.002
Caro-Vadillo, A., et al. (2023). Epidemiology of canine dilated cardiomyopathy in the United States from 2000–2019. Frontiers in Animal Science, 4, 1132345. https://doi.org/10.3389/fanim.2023.1132345
Freeman, L. M., Stern, J. A., Fries, R., Adin, D. B., & Rush, J. E. (2018). Diet-associated dilated cardiomyopathy in dogs: What do we know? Journal of the American Veterinary Medical Association, 253(11), 1390–1394. https://doi.org/10.2460/javma.253.11.1390
Kaplan, J. L., Stern, J. A., Fascetti, A. J., Larsen, J. A., Skolnik, H., Peddle, G. D., … Ontiveros, E. S. (2024). An 18-month prospective study evaluating the effects of dietary carbohydrate sources on cardiac health in healthy adult dogs. Journal of Animal Science. https://doi.org/10.1093/jas/skaf225
Kittleson, M. D., & Kienle, R. D. (1998). Small animal cardiovascular medicine. Mosby.
Ontiveros, E. S., Whelchel, B. D., Yu, J., et al. (2020). Development of dilated cardiomyopathy in dogs consuming diets with different protein sources. Journal of Veterinary Cardiology, 30, 1–11. https://doi.org/10.1016/j.jvc.2020.03.006