Dilated Cardiomyopathy (DCM) is a disease of the heart muscle, which results in dilation of the heart chambers. This, in turn, decreases the ability of the heart to pump efficiently, leading to buildup of fluid in the chest and abdomen, known as congestive heart failure. Two forms of DCM exist- primary and secondary. Primary DCM is presumed to be a hereditary disease, while secondary DCM is non-hereditary and can be caused by factors such as nutrition, infectious disease, and certain medications. Moreover, nutritional causes of secondary DCM can vary from nutrient deficiencies, such as taurine or vitamin B1 deficiency, to levels of nutrients or other dietary compounds, such as heavy metal toxicity. Unlike primary DCM, secondary DCM can improve with diet change.
In July 2018, the the United States Food and Drug Administration (FDA) announced it had begun investigating reports of canine dilated cardiomyopathy (DCM) in dogs eating certain pet foods, many labeled as “grain-free.” As of July, 2020, more than 1100 dogs with DCM had been reported to the FDA. Based on the data collected and analyzed by that time, they published a Q&A that stated, “emerging science appears to indicate that non-hereditary forms of DCM occur in dogs as a complex medical condition that may be affected by 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.” “Grain-free” diets were implicated early on, specifically those containing pulses. The FDA further elaborated on this, explaining that pulses have been used in pet foods for many years with no evidence to indicate that they are inherently dangerous, however these ingredients may be used in greater proportion in “grain-free” diets than in most grain-containing formulas.
Since 2018, sixteen peer-reviewed research articles on DCM have been published. No cause-effect relationship between grain-free diets and DCM was identified in any of the studies conducted by the FDA. Independent researchers also began studying this to understand potential links between certain diets and DCM. In June 2020, a review in the Journal of Animal Science compiled information on the research to date around incidence, symptoms, treatments and preventative measures, as well as potential causes of the disease. They concluded that DCM is the second most prevalent heart disease in dogs, affecting over 300,000 dogs in the United States at any given time, and that multiple dietary and environmental factors, in addition to genetics, can potentially lead to development of the disease.
A retrospective study published in December 2020, reviewed the medical records from 71 dogs diagnosed with DCM. Researchers concluded that dogs with DCM eating nontraditional diets experienced improvement in cardiac function after switching to a grain-inclusive diet, as well as treatment with medication and supplements, but that additional research was needed to examine possible associations between diet and DCM. In August 2021, a study looking into specific compounds found in grain-free diets vs grain inclusive diets, found that a series of chemical compounds could only be found in the former and that the source of those compounds was mainly peas. The authors stated that more research is needed to see if those compounds actually have an effect on DCM onset, but suggested that nutrient insufficiency may be the real culprit.
In December 2022, the FDA issued their fourth update on diet-associated dilated cardiomyopathy (DCM) in the form of frequently-asked questions. At this time, they also announced that they will no longer be updating the public on the potential link between certain diets and canine dilated cardiomyopathy until there is meaningful new scientific information to share. In the latest update, another 255 dogs with DCM had been reported to the FDA, bringing the total number of dogs with DCM reported to the FDA to 1,382. It is unclear whether this lower rate of dogs reported is due to there being fewer cases, or rather just fewer veterinarians and pet owners reporting cases. Regardless, in response to whether the diets associated with DCM have any commonalities, the FDA’s response was:
“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… 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.”
Although we may be closer to an answer, the cause of DCM remains unknown. Much research is still needed in this arena, and this remains an ongoing, collaborative scientific venture. The FDA’s update concluded by stating “We will also provide additional updates to notify the public if or when substantive scientific information comes to light.”