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Dilated cardiomyopathy (DCM) is a condition that prevents the heart from pumping properly.[1] It is more prevalent in some breeds, but there have been recent reports of increased rates of DCM in breeds prone to the condition when fed grain-free diets. While this should be investigated further, it is a loose correlation and has been blown out or proportion to the point of terrifying puppy parents that they are feeding their dogs a harmful diet. This condition has been falsely inflated by blog posts, poor or incomplete research, and some major companies taking advantage of the public panic.
Dr Ryan Yamka, a board certified veterinary nutritionist, wrote an excellent paper summarizing a talk he gave at a Veterinary Meeting (shared with his permission). His presentation was approved by the Society of Veterinary Medical Ethics.
Dr Yamka is a strong advocate for the rights of people to ask questions of their veterinarians and have open and two-way discussions. I agree with his recommendation to avoid veterinarians who won’t discuss your questions with you and answer any questions.
I’m summarizing his paper here to make it easier for busy people to review his points. With his permission, I'm including his paper for those who prefer to read it themselves (which I highly recommend—if at all possible always read sources!).
Dr Yamka's main point is that although there may be a possible correlation between DCM and grain-free food, this is not yet even close to proven, and the recent FDA release supports this. FDA specifically stated that they did not identify a direct link between grain free food and DCM.
Dr. Yamka's thoughts about the publication that started discussion of this topic.
Dr Lisa Freeman’s paper that started the confusion were anecdotal, not backed by any rigorous scientific study. People took this unreviewed conclusion of Dr Freeman’s and, out of fear, it embedded in our collective psyches. There was no data supporting her claims, only opinions.
Dr Freeman’s subsequent work had almost 60% of the DCM cases they reported associated with a single food brand (Acana). Important to note is that there was no control group in this study. If you aren’t familiar with study design, control groups are essential to showing the reliability of findings. Without controls, studies are not considered reliable.
Most brands are not “boutique” brands (as Dr Freeman claimed) and are in fact made by the larger pet food conglomerates and sold in pet and grocery stores nationwide.
Most food is not “exotic” (as Dr Freeman claimed), as 75% of the meat source in foods in the FDA report were common proteins (mostly chicken), 24% were unusual proteins, and 1% vegan.
The FDA investigations into the link between DCM and diet
When the FDA began investigating this topic, they had only 4 reported cases of atypical DCM (3 Golden Retrievers and 1 Labrador Retriever).
In their larger update in late 2019, FDA only reported the top 16 brands implicated, which captured headlines. What FDA failed to point out and what readers often failed to realize is that most of these foods are manufactured by one of the “Big 5” dog food manufacturers (Purina, Hill’s, Mars, Diamond, Smucker). Please see the paper for a sample listing of foods within these larger brands.
One of the largest problems with discussion of the FDA report was that FDA requested submission of cases related to grain free diets only—they did not ask for cases that involved grain-inclusive diets, so that obviously can lead to faulty conclusions about the number of cases of atypical DCM being associated with grain free diets only, since grain inclusive diets weren’t included in the study. (Despite FDA asking for grain-free only, almost 10% of the reports still involved grain-inclusive diets, which strongly suggests the need to investigate this further.)
The press failed to note the FDA comment that Golden Retrievers (the breed represented in the Freeman paper and represented in highest numbers in the FDA review) may be genetically predisposed to DCM. It is important to consider the potential genetic link, as DCM is known mostly as a genetic disease.
FDA analyzed the several foods “implicated” in DCM and concluded that none had any nutritional abnormalities and that results for both grain free and grain inclusive foods were similar. (Dr Yamka rightly points out that digestibility was not looked at—for more about digestibility, click here https://www.midwoofery.com/post/lets-talk-poop).
The FDA review noted there were several underlying conditions in many dogs in the study, which could be a factor in DCM as it is in other species (including humans). In fact, only a little over half of the dogs in the study were actually confirmed to have DCM.
FDA did NOT conclude grain free foods cause DCM, contrary to the interpretations in the press.
Dr Yamka gives a good overview toward the end of his paper about how grain-free foods came to be popular, so I recommend reading that if the topic interests you.
Takehome message: there is no data to support the idea that grain-free foods cause DCM.
FDA has not issued any recalls on foods for their potential relationship to DCM and has not advised people change foods based on this issue alone.
The remaining comments in this post are my own.
Why we need to stop the panic and focus on the root cause
For those who don’t know me well, I spent a good portion of my career involved in developing new treatments and therapeutic products (mostly human, but some veterinary). (I'm considered enough of an expert in the field that I designed and wrote curriculum for universities and colleges.) When a problem arises in manufacturing these products, the most important thing we do to prevent future issues is to find the root cause. Without the root cause, it’s much more likely for solutions to not be directed at the actual problem.
Therefore, I very strongly agree with Dr Yamka’s position that our primary objective should be in determining the root cause, and that includes looking beyond food to other factors. We should, of course, still keep diet in our search, but it should not be our only focus since there are so many other potential factors that could be involved.
How big is this issue?
Another point I want to make is that we have blown the DCM issue out of proportion. While this is not out of proportion for those whose individual dogs are suffering, for the majority of us it is a non-issue. Let’s look at some rates of occurrence to back up this claim. In some breeds, such as Dobermans or Golden Retrievers, the diseases has a strong genetic component. However, in most breeds, the prevalence is less than 1% of the population, and more common in larger breeds.[2]
Most cases of DCM are believed to have a heritable component, and many are also attributed to associated infections, although a single specific cause has not been identified[3]. The genetic component is supported by the higher prevalence in specific breeds. However, rates of occurrence are much higher for many other conditions, including hip dysplasia and other orthopedic conditions, cancers, communicable diseases, diabetes, and so much more.[4]
Reports of about 300 cases of nutritionally mediated DCM (NM-DCM) have been received by FDA.
This is horrible for those dogs and families affected, but it’s important to look at the bigger picture as well and realize that given there are 90 million dogs in the United States alone, this is a very, very low rate of occurrence.
Contrast that with the estimate 60% rate of cancer in breeds like Golden Retrievers. https://www.cbsnews.com/news/why-do-so-many-golden-retrievers-get-cancer-massive-study-hopes-to-find-out/
Since NM-DCM is associated with grain free diets, let’s factor that in. Grain free diets are fed to about 37% of the dog population in the US, based on market share[5], so that would give us about 33 million dogs eating a grain-free diet. Again, FDA has reports of 300 confirmed cases.
That gives us a rate of occurrence of 0.0009 percent.
Let’s take the worst-case devil’s advocate approach and assume NM-DCM is vastly under-reported by a huge factor, say of 100 times. Our hypothetical situation would mean that only 1 in 100 cases has been reported for a high profile condition and would give us the assumption there are 30,000 cases instead of the reported 300. With 33 million dogs in the population eating grain free food, that would give us a hypothetical rate of occurrence of 0.09 percent.
To see to an actual rate of 3 percent in the population, we would need to see almost a million dogs eating grain free food be affected with NM-DCM, which is so far from what has actually been reported as to be an absurd expectation. Contrast that with rates of hip dysplasia, pancreatitis, digestive issues, and other conditions that can be more soundly related to diet and have rates of occurrence of double digits in various canine populations.
My take-home thoughts
We do want to continue investigating this topic. We do want to find the true cause so we can help prevent DCM when possible. We do not, however, want to make rash decisions and potentially harmful changes based on fear rather than fact. We are very emotional about and attached to our dogs. This is not a bad thing. But we need to make our important decisions about their health from a point of objectivity and careful consideration. Knee-jerk reactions are too likely to come back and bite us on our proverbial tails.
In general I do not avoid peas or other legumes if they are not in the top few ingredients. I prefer real meat as a first ingredient. And I recommend food rotation to provide nutritional variety.[6]
Remember, feed the dog in front of you, not some vague notion of avoidance of an uncommon condition that likely has nothing to do with the dog you are feeding today.
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References
[1]This reference describes what DCM is: https://www.vet.cornell.edu/hospitals/companion-animal-hospital/cardiology/canine-dilated-cardiomyopathy-dcm
[2]Bulmer, BJ. “Managing dilated cardiomyopathy (Proceedings). https://www.dvm360.com/view/managing-dilated-cardiomyopathy-proceedings
[3]Nelson, OL. “Dilated Cardiomyopathy (DCM)” https://www.vetmed.wsu.edu/outreach/Pet-Health-Topics/categories/diseases/dilated-cardiomyopathy-in-dogs
[4]“List of Dog Diseases” https://en.wikipedia.org/wiki/List_of_dog_diseases
[5] This reference is where I obtained the market share data for grain free dog food: http://cdn2.hubspot.net/hubfs/2168539/2016_Pet_Food_Trends_and_APM_Brands.pdf?t=1484853966701
[6] This reference is a special topic review (a comprehensive survey of existing peer-reviewed research on a topic; considered a reliable source of current understanding) about what is known to date regarding DCM and diet in dogs: Wilfredo D Mansilla, Christopher P F Marinangeli, Kari J Ekenstedt, Jennifer A Larsen, Greg Aldrich, Daniel A Columbus, Lynn Weber, Sarah K Abood, Anna K Shoveller, Special topic: The association between pulse ingredients and canine dilated cardiomyopathy: addressing the knowledge gaps before establishing causation, Journal of Animal Science, Volume 97, Issue 3, March 2019, Pages 983–997, https://doi.org/10.1093/jas/sky488