Just a couple of years ago, dilated cardiomyopathy or DCM, a rare form of heart disease, wasn’t really on many people’s radars. Even amongst veterinarians, it was somewhat of an obscure disease and for members of the public, unless you were unlucky enough to own one of the handful of dogs or cats affected by the disease, chances are you had never heard of it. Fast forward to toady and DCM is the source of worry and confusion amongst pet owners all over the world and has resulted in a huge shift in pet food buying habits.
But how and why did we get from one state of affairs to the other? How worried should we be about DCM and, as many are suggesting, could there be more to this story than meets the eye?
What is DCM?
DCM is a rare but serious disease of the heart muscle that results in weakened contractions and poor pumping ability. As the disease progresses the heart chambers become enlarged, one or more valves may start to leak and signs of congestive heart failure can develop.
Although its cause is unclear, there is believed to be a genetic element to the disease as it appears to affect certain types of dogs more than others. Male dogs, for example, are more at risk than females and larger breeds (like Scottish Deerhounds, Irish Wolfhounds, Boxers, Dobermans and Great Danes) have a higher incidence than smaller breeds . This isn't to say that DCM does not occur in females or in smaller breeds, only that it is less common.
Taurine is the most abundant amino-acid in the heart and its deficiency has long been linked to DCM as well as other heart conditions. Some breeds that are known to be prone to taurine deficiency like Golden Retrievers and Cocker Spaniels have also been found to have an increased likelihood of developing DCM and in dogs diagnosed with taurine-deficient DCM, taurine supplementation has been found to improve the condition  so it is certainly part of the DCM puzzle.
Nevertheless, most dogs with DCM are not deficient in taurine at all. In fact, according to one set of statistics  only 14% of DCM cases have been found to be taurine deficient so it is far from the only factor at play.
How common is DCM?
Despite what you might think, DCM is not especially common, normally only affecting an estimated 0.5-1.1% of the adult dog population . Of course, these statistics are of little consolation if your dog is one of the unfortunate ones suffering from the condition but if not, the chances of it developing are usually very low.
However, a couple of years ago, a handful of US vets claimed to have seen an increase in cases of DCM and it is these reports that provided the spark for the entire DCM crisis that we find ourselves in today.
DCM and Diet
DCM is nothing new. Vets have been aware of it for decades and as far back as 2003 it was suggested that diet might play a part. At that time though all of the studies focussed on the taurine connection and it wasn't until much more recently that other ingredients and types of foods were being brought up in connection with DCM.
Dr Lisa Freeman
It was an article published by the US vet Dr Lisa Freeman in June 2018 that really thrust DCM into the spotlight for the first time.
For those who aren’t aware of her work, Dr Freeman is a long-time and very vocal advocate of ‘big pet food’, and, until this point, was best known for her vehement opposition to raw feeding. She also has some remarkable quotes to her name including such gems as “do yourself a favour – stop reading the ingredient list!”. Suffice to say, we at AADF are not her biggest fans.
Anyway, in her article entitled “A broken heart: Risk of heart disease in boutique or grain-free diets and exotic ingredients”, Dr Freeman stated that “some veterinary cardiologists have been reporting increased rates of DCM in dogs” and “there is suspicion that the disease is associated with eating boutique or grain-free diets”. On the basis of mostly hearsay and conjecture, Dr Freeman spends the entire article attempting to link the apparent rise in DCM with what she called ‘BEG’ foods (foods from 'Boutique' companies, foods containing 'Exotic ingredients' and Grain-free foods).
As tends to happen with ‘x is killing your dog’ pieces, this article and her follow up study  (both of which have come under enormous criticism ) were carried far and wide by the pet press and social media.
It's worth noting here that the term 'BEG' essentially encompasses all brands that aren't The Big Three or their subsidiaries: 'Boutique' meaning smaller or newer companies; 'exotic' meaning any ingredient that isn't run-of-the-mill; and Grain-Free being the category of choice for most competitor brands. Over the last decade or so, the 'BEG' producers have taken a large market share away from the established pet food multinationals. Certainly worth bearing in mind.
The FDA investigation
Just a month later, in July 2018, the FDA (America's Food & Drug Administration) announced that it was mounting an investigation into DCM with its now famous alert to pet owners .
Despite the brevity of the announcement, there really is a lot to unpack:
The distinct lack of facts. When you take away all of the padding information, you’re really left with just three facts:
The FDA had received a number of reports of DCM, at least some of which were in breeds not commonly affected by the disease. In a later update , it was revealed that the total number of reports between Jan 2014 and Nov 2018 were 21 for dogs and 3 for cats. That's an average of less than 5 reports per year.
The diets of the dogs affected 'frequently' (not universally) contained potatoes or legumes (e.g. peas, lentils etc) as main ingredients.
4 out of 8 of the dogs had taurine deficiency, the other 4 did not.
And that's really it.
The alarmist tone. Considering so little was known at this point, the announcement and particularly the headline and first paragraph are clearly unnecessarily provocative.
The massive leaps to conclusions. In the very first paragraph, the disease is directly and unequivocally linked to the consumption of "certain pet foods containing peas, lentils, other legume seeds, or potatoes as main ingredients" and later on it's noted that "high levels of legumes or potatoes appear to be more common in diets labeled as 'grain-free'".
Bearing in mind that the investigation HADN'T EVEN STARTED YET, these seem to be some fairly bold assertions to make.
It is these three factors together that have raised the suspicions of many in the pet community and, from an impartial stand point, it’s easy to see why.
To get anywhere near the truth of the matter, three questions really need to be asked: Why investigate in the first place? What are they actually investigating? and, perhaps most telling, who's going to benefit?
1. Why investigate?
As I mentioned earlier, everything started with reports from a number of US vets of an increasing number of dogs being diagnosed with DCM - particularly breeds of dogs that are not commonly associated with the disease. This point is routinely repeated in articles, studies and reports on the subject including the FDA’s own but nowhere are any figures provided either for how many vets the reports came from or for how large an increase they had witnessed.
As we’ve seen, the FDA’s alert tells us that, at that point, they had received an average of around 4 reports of canine DCM per year across the entire USA, some in breeds that are more prone to the disease, some in breeds that are less prone. Bearing in mind that DCM is estimated to affect at least 0.5% of the dog population and that no breeds are completely immune to the disease, do these figures really seem enough to warrant raising the alert and starting an investigation?
2. What are they actually investigating?
So, let’s say for some reason your answer to the above question is “yes, we need an investigation!”, what exactly should you investigate?
To any vaguely scientifically minded person, the first port of call should be to confirm the very basis of the whole discussion - whether the numbers of cases of DCM had indeed increased or not. Amazingly though, this pretty crucial question remains not only unanswered but seemingly unasked.
Naturally, reports of DCM certainly rose following the FDA’s initial alert but after such enormous publicity that's hardly surprising. To get a real gauge on whether incidence of the disease really is increasing, the only reliable data will be that from before the alert but, as we've discovered, these figures don’t seem to exist.
Ok, so let’s assume they were able to confirm a rise in the occurrence of DCM (again, they haven't) - where on earth should you start in trying to figure out what could be causing it? With dietary, environmental, genetic and lifestyle factors all at play, each of which comprising a multitude of different interacting elements, even identifying what to investigate in the first place should require detailed fact-finding from a large number of cases and a whole lot of ground work.
Also, since there weren't any indications of a rise in DCM outside of the US, you would presumably start by looking for something that is done differently in the US than in Europe.
Despite all of this, based on a handful of cases and the flimsiest of premises, the FDA immediately narrowed their investigation down to grain-free foods and the starches they generally contain (potatoes and legumes, all of which are just as popular outside of the US) and then, before any work was done, alerted the public to this ‘potential connection’.
The June 2019 Update
One year after the FDA announced their investigation into the potential connection between diet and DCM they issued an update on their progress so far . The data shared in the report was extensive but, while it may have made interesting reading (at least for a pet nutritionist), it fell a long way short of confirming any link between diet and DCM:
After the rise in reported cases of DCM since the alert the previous year, the total number of reported canine cases in the US had risen to 560.
As expected from what is already known about the condition, the overwhelming majority were from breeds already known to be genetically predisposed to the condition and males were more affected than females.
Most of the dogs were fed on dry foods. Again, quite predictable as most dogs in the population are fed on dry foods. A smaller number of cases were also reported on all other types of foods.
But there were also some less predictable findings:
91% of the dogs were fed on grain free foods and 93% of the dogs were fed on foods containing legumes as a main ingredient. The majority were also from smaller (aka ‘boutique’) producers.
These figures are certainly higher than you would expect but before jumping to any conclusions it is important to consider that the data was likely fundamentally flawed:
Almost all of the reported cases (539 out of 560) were submitted after and, in many cases, in response to, the FDA’s alert or the publicity that followed. As we’ve seen, both the alert and the associated media coverage specifically highlighted grain free foods and ‘boutique’ brands. This would have given the coverage a far higher reach with dog owners feeding those types of diets and would have made them much more vigilant for the condition. Vets too would likely not have been immune, being more watchful for and more likely to report cases of DCM in dogs on grain-free and/or boutique diets than those that were not.
It’s therefore reasonable to assume at least some data-skew would have taken place in favour of more reports from dogs fed on grain-free or boutique diets but how much is impossible to gauge.
According to the update and to their credit, not all of the investigators efforts have been in trying to prove a link between grain-free foods and DCM. Indeed, analyses into different meat sources, different food types (wet, dry, raw) and a handful of other factors have also been looked into but no correlations have yet been found.
The investigation is still ongoing but it is clear that it has a long way to go before any connections can be remotely confirmed.
3. Who benefits?
While we all hope that the investigation will uncover some crucial information that will help to reduce the number of pet DCM cases or aid in DCM patient recovery, it doesn’t seem particularly likely at this stage.
So if dogs aren't the beneficiaries of this whole debacle, who is?
I'm sure you've guessed by now but, whether by coincidence or design, The Big Three pet food producers and their affiliates have done very well out of DCM. The completely groundless attacks on so called 'BEG' foods, the highly suspect conduct of the FDA and the lazy and sensationalist reporting that followed has seen a huge shift of customers back onto Big Three brands.
To stress the point, this is not because their foods have been shown to be any healthier for our pets but because of the highly questionable actions of a handful of veterinary researchers and the FDA.
As things stand, this is really the only tangible consequence of the investigation and no matter what findings eventually emerge, the changes it has wrought on the pet food market will be difficult to undo. Indeed, the internet is now so awash with sites and articles repeating the same myth that grain-free pet food causes heart disease that customers are likely to be steering clear of them for years if not decades to come.
Now, I’m not saying the whole thing was a hatchet job by the pet food establishment to permanently damage the reputation of their primary competition all at the expense of the American taxpayer... but if you were planning such an endeavour, this is how you would do it.
Too long; Didn't read
To sum up:
We have a possible but unconfirmed rise in cases of DCM in the US.
The ongoing and probably unnecessary FDA investigation is yet to reveal any causal factors.
Shareholders in large pet food multinationals got richer.
If your dog has been diagnosed with DCM then that's obviously awful. Please consult with your vet and we’ll all keep our fingers crossed for a speedy recovery.
If not, then there’s really no reason to fret about it. There is always a chance your dog will be one of the 0.5-1.1% of dogs that develops the disease but, as far as we know right now, what you feed will not change those odds.
The FDA's investigation is likely to continue for a while yet and, who knows, it might actually find a concrete causal link between diet and DCM but right now it's impossible to say what that might be so all we can do is wait and see. Don't be coerced into changing your pet's diet and, most importantly, don't worry!
Dilated cardiomyopathies in dogs. Dr. Eric de Madron, DMV, Dipl. ACVIM (Cardiology)
and dipl. ECVIM (Internal Medicine). Link
FDA Investigating Potential Connection Between Diet and Cases of Canine Heart Disease Announcement. July 12, 2018. Link
FDA Update February 2019. FDA Provides Update on Investigation into Potential Connection Between Certain Diets and Cases of Canine Heart Disease. Link
FDA Update June 2019. Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy. June 27, 2019. Link
Questions & Answers: FDA Center for Veterinary Medicine’s Investigation into a Possible Connection Between Diet and Canine Heart Disease. June 27, 2019. Link
Torres, C. L., et al., Taurine status in normal dogs fed a commercial diet associated with taurine deficiency and dilated cardiomyopathy. J. Anim. Physiol. Anim. Nutr. 2003. 87(9-10): 359-372.
Lisa M. Freeman, DVM, PhD, DACVN. A broken heart: Risk of heart disease in boutique or grain-free diets and exotic ingredients. June 2018. Link
Lisa M. Freeman DVM, PhD et. al. Diet-associated dilated cardiomyopathy in dogs: what do we know? Decemnber 2018. Link
Daniel Schulof. Bad science and big business are behind the biggest pet food story in a decade. July 2019. Link
Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets. 31 Dec 2018: Kaplan JL et al. PLOS ONE 13(12). 2018. Link