After Six Years, What Do We Know About Diet-Related DCM?

In 2018, veterinarians, dog owners and even the FDA were scared into believing that Canine Dilated Cardiomyopathy (DCM) was on the rise. This “scare” was prompted by an opinion piece by Lisa M. Freeman et al published in the Journal of the American Veterinary Medical Association.1 Their opinion implied that “BEG” (boutique, exotic and grain-free) diets were causing the supposed increase.

While the term BEG diets is so broad that it includes virtually any dog food not produced by the three or four largest manufacturers, veterinarians jumped on the idea. Veterinarians have used the article, submitted without evidence or peer-reviewed/published researched to support its claims, to convince pet companions the grain-free diets were bad and that they should only feed grain-inclusive diets to their dogs. Now, more than six years later, what have we learned about the “DCM scare” and the association with BEG diets and grain-free diets in particular?

  1. DCM is not actually on the rise due to BEG diets or any other cause.
  2. The reports that started the scare were biased and incomplete.
  3. Research conducted since 2018 has failed to establish a link between BEG diets and DCM.
  4. Feeding a grain-inclusive diet does not prevent or reduce the risk of developing DCM.
  5. Dogs fed “nontraditional” (i.e. grain-free) diets that develop DCM recover faster and live longer.
  6. The FDA has taken no action against a product or company as a result of its investigation.

First, Canine DCM is not on the rise due to feeding grain-free food or any other reason.

We know this thanks to an actual retrospective study published in Frontiers of Animal Science in 2022.2 Looking at a span from 2000 and 2019, it found that the overall incidence rate of DCM remained unchanged during that time period. The authors concluded: “Our data do not support a correlation between grain-free dog food and DCM phenotype.”

It is important to note that grain-free diet sales increased by more than 500% between 2009 and 2019, going from $900 million to over $5.4 billion in 2019.2 If there were any correlation between grain-free diets and DCM as Freeman et al implied, the incident rate should have risen significantly during that time frame. It did not.

However, following the DCM scare makers of “traditional” grain-inclusive diets saw their sales soar. Hill’s Pet Foods’ sales increased from $2.29 billion in 2017 to $3.71 billion in 2022. Purina saw a 25% increase in sales during the same time period.3 All at the expense of smaller manufacturers within the so-called BEG category.

Second, Freeman et al appear to have biased the FDA investigation by only reporting cases tied to their so-called BEG diet category.

According to AP news, “agency records show that for the initial study, some vets were instructed to submit only dilated cardiomyopathy (DCM) cases that implicated grain-free, “exotic” or “boutique” pet foods.” 4

Thanks to a law suit filed in February, 2024 we know that the protocol used for reporting stated: “If patient is eating any diet besides those made by well-known, reputable companies or if eating a boutique, exotic ingredient, or grain-free (BEG) diet … Report case to the FDA.”3

By seeking to exclude grain-inclusive diets made by the largest manufacturers, Freeman et al created a picture for the FDA that looked like DCM related to grain-free diets was on the rise, while at the same time ignoring DCM related to “traditional” grain-inclusive diets.

McCauley et al5 suggest that “moreover, regardless of what diet the dog is eating, asking the veterinary community and the public for DCM cases in dogs only eating grain-free or exotic protein diets will result in sampling bias (Pannucci and Wilkins, 2010)6. To prevent this, the veterinary community should be asked to provide information for all DCM cases during the same time period, regardless of what the practitioners’ proposed etiology was.”

Furthermore, FDA reports from documented cases do not have complete medical records and diet histories for all dogs, which is critical to even begin linking the cause of DCM to a specific part of the diet. In fact, Dr. Freeman7 herself concluded in 2003 (before grain-free diets were common) that: “Dietary intake for dogs with cardiac disease is highly variable and often not optimal.”

Freeman et al also admitted in their original opinion article that “it (DCM) may possibly be a result of another dietary component (eg, treats, chews, or supplements) commonly fed to dogs eating these diets.”1

We do not know if the misleading nature of the researchers’ implications were deliberate or just bad science. We do know that the researchers responsible receive extensive grants, consulting fees and other support from the largest manufacturers of traditional grain-inclusive diets. We also know that the growth of BEG (boutique, exotic and grain-free) was having a significant financial impact on those manufacturers.

Third, actual research has not established any connection between grain-free diet (including those with legumes) and DCM.

While a number of research studies since the initial scare have titles that seem to imply a connection between grain-free diets and DCM, their conclusions are just the opposite. Here are some of the conclusions from recent research:

  • “a cause-and-effect relationship [between DCM and grain free diets] cannot be proven,” 20188
  • “Dietary induced DCM associated with some GF diets remains unproven,” 20199
  • “The correct characterization of diets that are associated with DCM is unknown because the cause has not yet been identified,” 202110
  • “although these retrospective data allow for exploration of hypotheses of associations between diet and DCM, a causal relationship cannot be determined,” 202111
  • “Despite ongoing research efforts since the first reports of diet-associated DCM, the causal dietary components and mechanisms have remained elusive,” 202212

Unfortunately, while researchers are spending significant effort and money chasing the connection to grain-free diets and DCM, they are ignoring broader issues related to diet and disease.

Fourth, feeding grain-inclusive dry food does not prevent Canine DCM.

The FDA itself has stated, “FDA has received reports of non-hereditary DCM associated with both grain-free and grain-containing diets.”

In 2010, before grain-free diets became popular, DCM was recognized as the second most common canine heart disease in the country5 —suggesting that the disease was already impacting possibly 300,000 to more than 1 million dogs at any given time5. In fact, as far back as 1988, researchers were publishing studies related to DCM in dogs.13

So while many veterinarians still recommend switching dogs from grain-free to grain-inclusive diets, the switch is not supported by science nor does it insure dogs will be protected from DCM. In some cases it could possibly increase the risk. Unfortunately, no one knows.

On the other hand, veterinarians are not talking about how switching to a traditional grain-inclusive diet may lead to a host of other issues besides DCM. We are saddened that the discussion about DCM has overshadowed the reasons why grain-free diets became so popular in the first place: The poor health of many dogs fed grain-inclusive diets.

At Healthy Pets Northwest, we have always suspected that the contamination of grains with herbicides, pesticides, mycotoxins, and fertilizers impacted a pet’s health. Those substances affect the gut microbiome of dogs which disrupts absorption of nutrients and lessens immune response. The removal of those dietary contaminants may help explain why we have seen such improvements in overall health when dogs were switched from traditional diets to grain-free diets.

Fifth, dogs fed “nontraditional” diets that develop DCM recover faster and live longer than those fed traditional grain-inclusive diets.

A study published in 2022 by Freeman et al14 found that dogs eating “nontraditional diets” when they developed DCM recovered faster and lived, on average, more than three times longer than dogs that developed DCM eating “traditional” grain-inclusive diets. Of course, according to Freeman et al, those dogs eating “nontraditional” BEG diets should have been sicker at the start so the reason for the improvement was unknown.

Another interesting note is that dogs suffering from diet related DCM improve with treatment and diet change, even when that change is to a grain-free diet.

Sixth, the FDA has taken no action against a product or company as a result of its investigation

Because of the research community ‘s failure to link grain-free or BEG diets to dietary DCM, the FDA has not issued a recall or removed any products from the market. The FDA stated, “FDA has no definitive information indicating that the diets are inherently unsafe and need to be removed from the market, but we are continuing to work with stakeholders in assessing how the diets may interact with other factors that may be impacting non-hereditary DCM.”

On December 23, 2022, the FDA stopped issuing public statements about diet-related DCM “until there is meaningful new scientific information to share.”

Where do we go from here?

Now that I have reviewed what we know about diet-related DCM, which may appear to be more a case of what we don’t know, the question for pet owners is how to move forward in a way that provides the most protection for your canine family member.

I’ll explore options and ideas in future blogs. My discussions will include some things the FDA and researchers chose to ignore. In the meantime, please review our blog on How Much Raw Food Is Enough?

References

  1. Freeman L. M., Stern J. A., Fries R., Adin D. B., and Rush J. E.. 2018. Diet-associated dilated cardiomyopathy in dogs: what do we know? J. Am. Vet. Med. Assoc. 253:1390–1394. doi: 10.2460/javma.253.11.1390
  2. Quest B. W., Leach S. B., Garimella S., Konie A., Clark S. D. (2022). Incidence of canine dilated cardiomyopathy diagnosed at referral institutes and grain-free pet food store sales: A retrospective survey. Front. Anim. Sci. 3 (3846227). doi: 10.3389/fanim.2022.846227
  3. Ketonatural Pet Foods, Inc v Hill’s Pet Nurtition, et al, case 2:24-cv-02046, United States District Court of Kansas.
  4. How canine heart disease was tied to grain-free dog food, Helen Santoro, AP, Published 10:08 AM PDT, July 23, 2022
  5. Sydney R McCauley, Stephanie D Clark, Bradley W Quest, Renee M Streeter, and Eva M Oxford (2022).Review of canine dilated cardiomyopathy in the wake of diet-associated concerns. J Anim Sci. 2020 Jun; 98(6): skaa155. Published online 2020 Jun 15. doi: 10.1093/jas/skaa155
  6. Pannucci C. J., and Wilkins E. G.. 2010. Identifying and avoiding bias in research. Plast. Reconstr. Surg. 126:619–625. doi: 10.1097/PRS.0b013e3181de24bc
  7. Freeman L. M., Rush J. E., Cahalane A. K., Kaplan P. M., and Markwell P. J.. 2003. Evaluation of dietary patterns in dogs with cardiac disease. J. Am. Vet. Med. Assoc. 223:1301–1305. doi: 10.2460/javma.2003.223.1301
  8. Adin D, DeFrancesco TC, Keene B, et al. Echocardiographic phenotype of canine dilated cardiomyopathy differs based on diet type, J Vet Cardiol. 21:1-9 (2019)
  9. Adin D, Freeman LM, Stepien R, et al., Effect of diet type on circulating taurine concentrations, cardiac biomarkers, and echocardiograms in four dog breeds, J Vet Intern Med., 35:771-779(2021)
  10. Freid KJ, Freeman LM, Rush JE, et al., Retrospective study of dilated cardiomyopathy in dogs, J Vet Intern Med. 35:58-67 (2021)
  11. Smith CE, Parnell LD, Lai C-Q, et al., Metabolomic profiling in dogs with dilated cardiomyopathy eating non-traditional or traditional diets and in healthy controls, Sci.Rep., 12, 22585 (2022)
  12. Fioretti M., and Delli C.. 1988. Epidemiological survey of dilatative cardiomyopathy in dogs. Veterinaria. 2(8):1
  13. Freeman L, Rush J, Adin D, et al. Prospective study of dilated cardiomyopathy in dogs eating non-traditional or traditional diets and in dogs with subclinical cardiac abnormalities, J. Vet. Intern. Med., 36:451-463 (2022)
  14. Freeman L. M., Rush J. E., Brown D. J., and Roudebush P.. 2001. Relationship between circulating and dietary taurine concentrations in dogs with dilated cardiomyopathy. Vet. Ther. 2(4):370–378.