Investigating Diet-Related Dilated Cardiomyopathy in Dogs – It’s Complicated
In July 2018, the FDA alerted pet owners and veterinarians about increased reports of dilated cardiomyopathy (DCM) in dogs. Affected dogs were not breeds or mixes thereof known to have a genetic predisposition for DCM and they were often reported as eating diets with peas, lentils, other legume seeds (pulses), and/or potatoes in various forms (whole, flour, protein, etc.) as main ingredients. The FDA and veterinary professionals began investigations into the issue, but a clear cause for the apparent increase in diet-related DCM has been elusive.
Dilated cardiomyopathy (DCM) is a disease where the heart becomes enlarged and the muscle cannot contract or pump adequately to provide normal blood flow throughout the body. Clinical signs in dogs include increased heart rate, coughing, difficulty breathing, weakness, and fainting. Arrhythmias, congestive heart failure, or sudden death are also possible. Treatment involves the use of medications to support heart function and remove excess fluid from the lungs. Unfortunately, the disease is rarely reversible except in a small number of cases that respond to supplementation with the amino acid taurine.
The association between diet and DCM is unproven. If real, the relationship is likely complex because there are many factors that could influence disease development:
Are pet foods deficient in specific nutrients?
Are the nutrients present in the diet, but not adequately digestible or usable for the dog?
Is something inhibiting uptake or usage of the amino acid taurine (or its precursors) which is important for heart cell function?
Are nutrient interactions in dog foods causing the problem?
Are toxins present in the food?
Are certain dogs genetically predisposed to this nutritional imbalance?
With so many possibilities to sort through, the AKC Canine Health Foundation (CHF) and its donors are supporting the investigation with CHF Grant 02661: Investigation into Diet-Associated Dilated Cardiomyopathy in Dogs. This grant provides funding for a multi-institutional, prospective evaluation of apparently healthy dogs. Investigators are comparing various measures of heart health in dogs eating grain-free diets and diets with peas, lentils, or potatoes as main ingredients to those in dogs eating grain-inclusive diets and diets without peas, lentils, or potatoes as main ingredients. They will use this information to determine if differences in the structure and function of the heart vary based on diet type in outwardly healthy dogs. Most of the recent clinical reports of suspected diet-related DCM have described dogs suffering from advanced heart disease. This investigation of outwardly healthy dogs is important to determine if evidence of heart disease is present at an earlier stage.
Initial results from this study were recently published in the Journal of Veterinary Internal Medicine1 and provide an important, objective analysis.
Diets were classified and compared in two ways: grain-free versus grain-inclusive and those with peas, lentils, and potatoes in the first ten ingredients versus those without peas, lentils, and potatoes in the first ten ingredients. All diets were commercial kibble and dogs had to be eating the same, single diet for six months prior to examination.
Four specific breeds were examined: Doberman Pinschers which have a known genetic predisposition to DCM, Golden Retrievers which were over-represented in reports to the FDA, and two breeds with no known genetic predisposition to DCM – Whippets and Miniature Schnauzers.
Investigators performed echocardiograms, measured blood and plasma taurine concentrations, measured cardiac biomarkers (NT-proBNP which is an indicator of cardiac stretch and cardiac troponin I which is an indicator of cardiac injury), and screened Doberman Pinschers for two genetic mutations associated with DCM in this breed.
Although no differences were found for echocardiographic measurements between diet types, the major finding from this study was that cardiac troponin I levels were higher in dogs eating grain-free dog foods or dog foods with peas, lentils, or potatoes in the top ten ingredients, compared to dogs eating foods without these qualities. Cardiac troponin I is a marker of heart muscle injury. Therefore, the finding of even low-level cardiac troponin I elevations in these outwardly healthy dogs suggests that there could be heart muscle cell damage even before any changes in heart size or overall function are apparent on the ultrasound exam of the heart. The clinical importance of the higher cardiac troponin I levels requires more research, but this finding adds a piece of information to a very large and complex puzzle.
There are limitations to the current study that should be considered when interpreting the results. The results only apply to the four dog breeds evaluated and analyzing the combined results could have hidden significant differences in heart variables within an individual breed. However, this study was not powered to examine these breeds individually. Additionally, there was an unequal number of dogs in each diet group, evaluation did not eliminate all possible causes of higher cardiac troponin I in dogs eating grain-free diets or those with peas, lentils, or potatoes as main ingredients, and the prevalence of arrhythmias was not evaluated. Finally, accurate diet classification is an area of uncertainty and could change with future research. Despite these limitations, this study contributes new knowledge to this important issue in canine medicine and will guide future research endeavors.
While owners and veterinarians are anxious for answers, the AKC Canine Health Foundation and its donors remain committed to the arduous task of scientific study needed to find accurate information. Learn more about this study and how you can participate here.
- Adin, D, Freeman, L, Stepien, R, et al. Effect of type of diet on blood and plasma taurine concentrations, cardiac biomarkers, and echocardiograms in 4 dog breeds. J Vet Intern Med. 2021; 1– 15. https://doi.org/10.1111/jvim.16075
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