DCM in Dogs – Is it diet or genetics?

Prior to the 2018 FDA report on DCM or Dilated Cardiomyopathy in dogs – DCM was largely considered a genetic disease associated with only a few breeds: namely Doberman Pinchers, Great Danes, Boxers and Cocker Spaniels. However in 2016 cardiology specialist started to see an increased number of cases of DCM that were not associated with the typical genetic breeds – due to this increase they started to collect data to find out if there was any correlation between the cases.

And what they found turned the pet food world upside down. I remember when the original FDA 2018 report on Grain Free Diets and DCM. At the time there was a lot of mis-information, and over-exaggeration from the media which fueled the fires on a report from the FDA that was largely correlative at the time. And as we know – correlation doesn’t equal causation.

Since then researchers have analyzed both the current cases, and applied what we knew in research at the time, along with performed additional research studies in order to give us a better understanding of what MIGHT be going on. However – we still do not KNOW exactly the cause of these cases.

So what is Dilated Cardiomyopathy?

DCM is a medical condition in which the heart’s ability to pump blood is lessened because the chambers of the heart become enlarged and weakened. In other words the heart muscle becomes so thin and stretched out that it can’t produce enough force to move blood from one area to the other.

When blood doesn’t move through the body properly a couple of things happen….

• The first is that the body will not receive nutrients and oxygen as it normally does.
• The second is that because the blood is not able to exchange nutrients and water efficiently throughout the body, fluid backs up in places it shouldn’t be – such as the lungs, or abdomen.
• The third is the the heart tries to compensate in order to maintenance overall balance (or homeostasis) within the body by pumping harder and faster.

These factors can lead to multiple different types of clinical signs – from very mild such as general lethargy or very severe such as sudden death.

What are the Clinical Signs of DCM?

• Weakness / Lethargy
• Shortness of Breath
• Collapse
• Coughing
• Excessive panting
• Fluid retention in the abdomen (causing a pot-bellied appearance)
• Rapid Heart Rate
• Abnormal Heart Rate
• Fainting
• Shock

If you notice your pup is having any of these clinical signs, contact your veterinarian for an appointment!

Since the average age of onset (according to the FDA 2018 report on DCM) was 6 ½ years old it is very possible that many of the symptoms of DCM may be accidentally brushed off as signs of “aging” in our pups – especially our larger breeds.

Dilated Cardiomyopathy as a Genetic Disease – What we know.

Prior to the 2018 FDA report – DCM was thought to be mainly a genetic condition, most commonly seen in Doberman Pinschers, Great Danes, Boxers, and Cocker Spaniels. Each of these breeds actually have a different root cause of Dilated Cardiomyopathy.

• Doberman Pinscher themselves actually have two different genetic mutations that make them predisposed to DCM. Often clinical signs are so mild that DCM in Dobermans has actually been called “Sudden Death Syndrome”. 
• Boxers are known to have carnitine deficiency related DCM: the cause of this deficiency is still unknown. However carnitine serves as a transporter of essential fatty acids – which function of fuel for different muscles (including the heart) within the body. Without carnitine it can cause a cascading effect that leads to problems with muscle & heart function.
• Cocker Spaniels are known to have Taurine responsive DCM: the cause of this isn’t 100% known as of this time, but what we do know is that supplementation of taurine does actually solve this issue. Taurine is used within the body to support nerve growth, and when deficient basically causes nerves in the sympathetic system to stop functioning as they should (and since the heart functions in this sympathetic nervous system, it can be heavily affected by deficiency).

The 2018 DCM FDA Report – What does it tell us?

The long and short of it is that the FDA report tells us there might be a potential issue, and that it may be related to a variety of different problems. However it doesn’t tell of which of those issues it the actual cause. 

The 2018 FDA report on DCM in dogs looked at the diet and presentation of 515 dogs that developed DCM. And it uses multiple graphics to depict different possible correlations that they are potentially further investigating. It also “named” the most common pet food companies that were fed during the report.

TOP PET FOODS MENTIONED IN REPORT

• Champion Pet Foods (Acana + Orijen) = 79 or 15% of cases
• Zignature (by Pet’s Global, manufactured by Tuffy’s/KLN) = 64 or 12% of cases
• Taste of the Wild (by Schell and Kampeter, manufactured by Diamond Pet Foods) = 53 or 10% of cases
• 4Health (by Tractor Supply Company, manufactured by Diamond Pet foods) = 32 or 6% of cases
• Earthborn Holistic (by Midwestern Pet Foods) = 32 or 6% of cases
• Blue Buffalo (by General Mills) = 31 or 6% of cases
• Kirkland Nature’s Domain (Costco Brand, manufactured by Diamond Pet Foods) = 29 or 5.5% of cases
• Fromm (Fromm Family Foods)= 24 or 4.5% of cases
• Merrick (Nestle Purina) = 16 or 3% of cases
• California Naturals (Mars Petcare)= 15 or 3% of cases
• Natural Balance (JM Smucker) = 15 or 3% of cases
• Nature’s Variety (MI Industries) = 11 or 2% of cases
• Nutrisource (KLN Family Brands) = 10 or 2% of cases
• Nutro (Mars Petcare) = 10 or 2% of cases
• Rachel Ray Nutrish (JM Smucker) = 10 or 2% of cases
• All other individual brands make up less than 1% each.

But of course as we all know correlation doesn’t not equal causation, and just like each of the breeds mentioned above have different CAUSES to DCM, it’s very possible that this list of cases has multiple different causes that will show up over time as this is researched further by veterinary cardiologists and the FDA.

But I do want to highlight one thing – there definitely IS something going on, and it IS partially diet related. The reason we know this is that for some of these cases, “treatment” was simply switching the dog from their old diet, to a new diet.

What is the FDA and specialists looking into as possible causes of DCM?

1. GRAIN FREE DIETS

In the original FDA reported cases they found that 90% of the diets that were mentioned were actually grain-free diets. Which has leads researchers and specialists to believe there may be something within grain free diets such as anti-nutrient compounds, or even digestibility issues that are associated with grain-free.

Of the diets mentioned 42% contained potatoes.

It should be mentioned that 10% of the diets included were NOT grain-free – these diets were either vegan/vegetarian OR were conventional diets containing grains. This suggests again, that this issue may go beyond JUST being related to grain free diets, which is why more research is needed.

2. TAURINE

The original FDA report showed that 42% of the dogs actually had taurine deficiency, which was fairly significant and pointed to an actionable area where specialists could easily test patients. Further research has found that the number of DCM cases related to taurine deficiency was actually closer to 10% and they have found this mostly associated with Golden Retrievers.

Board Certified Veterinary Nutritionists at the Tufts Veterinary School hypothesize that the higher number of taurine deficient cases in the original 2018 report could correlate with the higher number Golden Retrievers present in the original report.

3. LEGUMES

Another area where specialists and researchers are further investigating is legumes – this includes peas, beans, and lentils. A total of 93% of the diets reported contained some type of legume in them. By itself this definitely warrants further research – however what you should know is that there is already research that suggests that higher percentages of soy products (over 15%) can cause issues with digestibility of essential amino acids, and decrease protein digestibility.

According to an academic review paper published in March of 2019 evaluating the top diets implicated in the 2018 FDA report they believed that…

 “Based on the authors assessment of current formulas in the market, there is a high likelihood that legume seed use in some foods may be greater than 40%”

Which is well above the 15% mark that was suggested in the previous study – suggesting a diet associated formulation issue may be the root cause of this problem. However further research is definitely needed in order to assess this completely.

AUTHOR'S NOTE:
Since publishing this blog post in October of 2020 two main pieces of research have come out suggesting legumes - in particular peas - as being the possible culprit of many of our cases of Nutritional DCM in Dogs. A study from Feb 2021 found that dogs fed diets high in legumes for over a year started to have changes to blood parameters suggesting early heart disease. And most recently a research study from Aug 2021 found a high correlation between biochemical compounds that may negatively affect the heart and diets containing peas. 

4. NOVEL PROTEIN DIGESTIBILITY

Novel proteins have always been something that board certified veterinary nutritionists have been cautious about – and I know personally during many veterinary conferences representatives of different dog food companies will speak about how careful they are with researching novel protein digestibility in their foods. And though those feeding trials they will mention are unpublished, there are published studies that show differences in digestibility of different proteins.

The most significant of which was a study evaluating the use of three different meat meals – fish, chicken and lamb – for use in dog food. The study found the following digestibility for these proteins: 87% fish digestible, 80% chicken digestible, 71% lamb digestible. Not only did lamb meal have poor digestibility in the dog – the lamb diet was actually DEFICIENT in an essential amino acid DUE TO it’s poor digestibility. This essential amino acid, methionine, happens to be a precursor to taurine.

These researchers had formulated ALL THREE diets to be complete and balanced based upon current research at the time – but they did not account for lamb being that poor of digestibility.

If we take this study and apply this to the diets listed within the FDA report – it is possible that we just don’t have the current research on these novel proteins, and we just “ don’t know what we don’t know “ concerning these novel ingredients.

And this is particularly concerning because A MAJORITY of pet foods on the market today have NO RESEARCH done on them at all. Over 90% of foods have not even undergone AAFCO Feeding trials so establish very basic levels of safety to products. Ideally ALL foods should undergo extensive safety testing to look at digestibility and overall health of the pets eating them.

5. FIBER

The amount of fiber and the type of fiber within a diet can influence the overall digestibility of a diet, and peas and legumes are higher in fiber than traditional gains such as rice, this is another area that specialists are looking into, and that could influence/cause dilated cardiomyopathy in dogs.

One thing you need to know is that dogs actually DO NOT have a fiber requirement. Meaning that there is no AAFCO nutrient requirement for dietary fiber. Digestibility of nutrients based on fiber concent can be predicted, however it cannot be predicted based off of the crude fiber % listed on the pet food label. It can be predicted off of the total fiber – which is a combination of both the soluble and insoluble fiber within the food item.

This means in order to do accurate predictions on digestibility of products foods must be analyzed using measurements beyond the standard AAFCO nutrient profile in order to predict digestibility. 

These calculations are ones that would be done by a board certified veterinary nutritionist or specialist during the formulation of a pet food. However, since it is not required to work with these specialists in order to formulate and manufacture pet food it is possible that some diets will not have done fiber digestibility calculations.

6. GENETICS

The final area that researchers are actively investigating is genetics. Most of the dog breeds mentioned in the original report were large breed dogs, and of certain breeds. This suggests a possible genetic link, at least partially to DCM. Research published in 2019 has already been done looking at Golden Retrievers in regards to this issue.

The study looked at 86 golden retrievers – half of which were fed grain-inclusive diets, and half of which were fed a grain-free diet (that included potatoes or legumes and was part of the 2018 FDA report).

What they found in the study was that dogs fed grain-free diets had a lower whole blood taurine level in comparison to dogs fed a grain-inclusive diet. They also found changes upon echo-cardiogram suggesting dilated cardiomyopathy.

This study suggests a possible link between diet digestibility and golden retrievers – which is actually not new – previous studies in 2005 actually found that a very small subset of Goldens do have Taurine deficient DCM. However at the time the percentage was very low. Researchers of the current 2019 study predict that the increased numbers of DCM cases related to Golden Retrievers has to do with the increased popularity of grain-free diets since 2005.

However further research still needs to be done looking into the other popular breeds listed within the FDA report to see if there are other possible genetic + dietary links.

THERE MAY BE MORE reasons why dogs are getting this condition

These are just the top ones that I have found mentioned by specialists online. It’s very possible that through research we may find that one, or more of these issues are coming into play.

We may also find something else entirely that is causing these problems – such as links to certain medical conditions (like IBD, food allergies/intolerances, or hypothyroidism) where dogs may have issues with nutrient absorption and digestibility.

This issue is still very much unresolved, and may stay that way for a while since there are SO MANY potential causes.

What can we do as a pet owner going forward to prevent DCM in dogs and mitigate risks associated with possible diet-associated DCM?

1. Know the clinical signs of dilated cardiomyopathy and if you notice that your pup is displaying these signs – schedule an appointment for your dog to be seen by your veterinarian.
2. Discuss your pet’s diet with your veterinarian to decide the best diet for your pet’s current needs.
3. Question your Dog’s pet food manufacturer – in my opinion your dog’s pet food company should WANT to answer all your questions regarding their diets. I have a full breakdown on what questions to ask, along with how to choose a pet food on this blog post.
4. If you are feeding a “suspected” diet or if your dog is a “suspected” breed that is associated with DCM according to the DCM report – get your dog tested. Ask your veterinarian for a Whole Blood Taurine Test and potentially an Echo-cardiogram.

I hope this breakdown of the link between diet and dilated cardiomyopathy is helpful for you and your pup! If you are looking for more information about this topic, make sure to subscribe below – I will make sure to post new content as research progresses further in this topic. In the meanwhile some other great resources to bookmark are:

• Diet-Associated Dilated Cardiomyopathy Facebook Group
• FDA Dilated Cardiomyopathy Report
• Tufts Veterinary Nutrition