Diet-Associated DCM in Dogs – Where are we now in 2021?

Since the original FDA announcement in 2018 several groups of researchers including board-certified veterinary cardiologists, board-certified veterinary nutritionists, toxicologists, and more have come together to figure out what is causing a new type of Dilated Cardiomyopathy in Dogs.

The original 2018 FDA press release describes reports brought to the FDA by cardiology specialists with two main groups of dogs on grain-free diets. One group of dogs was breeds that we know have been associated with DCM in the past – Great Danes, Dobermans, Goldens and Labradors etc – these dogs on grain-free diets had low whole blood taurine levels. The second group was breeds not commonly associated with DCM – Shi-Tzu, Whippets, Chihuahuas, etc – who were fed grain-free diets with DCM but did not have low whole blood taurine.

Though the FDA and researchers were currently investigating other causes than diet – including genetics, toxins, infectious disease, parasites, and more – the one correlation that was most prominent between cases seemed to be that over 90% of dogs were eating a grain-free diet.

What is Dilated Cardiomyopathy in Dogs?

What you first need to understand before we get too far into the research on this topic is that prior to 2018 there were several known types of Dilated Cardiomyopathy.

The first type is called primary dilated cardiomyopathy. Primary DCM is a progressive disease that cannot be reversed by diet change or supplementation – you can manage the condition with medication, and give supplements to support the heart. But dogs do not resolve. This is the form of DCM that most people think of and if you have a Doberman, you can actually test the DCM1 or DCM2 gene.

The second type is called secondary dilated cardiomyopathy. Secondary DCM can be reversible if caught early enough in the disease process through supplementation, and medication. These dogs can be fully be resolved if given the chance. This form of DCM is less common and found in particular breeds – Boxers, Spaniels, and seen in some Large/Giant Breed Dogs. There are many different causes of secondary DCM in dogs – ranging from taurine/carnitine deficiency to infection, parasites, and even related to certain antibiotics (adriamycin).

What are the Clinical Signs of DCM in Dogs?

Probably the hardest part about the diagnosis of Dilated Cardiomyopathy in dogs is that the clinical signs are largely silent unless you are doing very specific heart-related testing. DCM is commonly called Sudden Death Syndrome because of it’s silent nature. Meaning sometimes dogs will act completely normal until they pass out, and go through cardiac arrest.

But sometimes dogs will express clinical signs of the disease. These dogs will usually show:

• Shortness of Breath / Excessive Panting
• Coughing or a Wet Cough
• Exercise Intolerance, or Tiring more Easily
• Fainting
• Eating Less or Difficulty Eating (due to problems breathing)
• Fluid build-up in the abdomen (which can present as sudden weight gain)
• Rapid Breathing while Sleeping (more than 40 breaths per minute when sleeping)
• Lethargy

Diagnosis of Dilated Cardiomyopathy in Dogs

Though listening to your dog’s heart may catch a heart murmur which could lead to a referral to a specialist – the typical physical examination or an Xray will not catch or be able to diagnose DCM in dogs. 

The only way to diagnose DCM is to do an Echocardiogram, which looks at the fluid volume, stroke volume, and movement of blood within the heart, along with the overall shape of the heart chambers. Though some veterinarians may measure whole blood and plasma taurine, or carnitine to check for nutritional deficiencies – these are not accurate screening tests for DCM, as not all dogs with DCM will have these deficiencies.

When we look at the FDA Reports (in particular their presentation done at Kansas State University in 2020)- less than 50% of the cases have a taurine deficiency. Meaning if using taurine levels alone as a screening tool we would miss half the cases.

How many cases are there of DCM in Dogs?

According to the FDA they have received over 1100 reported cases on non-hereditary DCM in dogs between 2015 to July 2020. Mind you that these are diagnosed cases, not just reported cases of DCM – meaning that the FDA is excluding cases of hereditary DCM, and those without a firm diagnosis via echocardiogram. Also prior to the original FDA announcement in 2018, we only had 5 reported cases.

I think it is important to mention that though reported cases may be “low” – heart conditions like DCM are extremely difficult to diagnose. It’s not as simple as running a simple blood panel – echocardiograms are not routinely performed on healthy dogs, nor are they inexpensive.

Personally, I know in our area an examination with a specialist with cost a good $100 USD, with an additional $500 or more for just the echocardiogram. And with only a bit over 300 board-certified veterinary cardiologists in the USA access to a specialist may be limited depending on where you live. Clinical signs are also vague and can remain hidden until the end stages of the disease.

How is Diet-Associated DCM treated once Diagnosed in Dogs?

This can largely depend on the dog’s particular case. Because DCM is difficult to find until later stages of disease – many dogs who have DCM will also have advanced stages of heart disease such as Congestive Heart Failure (CHF). These dogs will need a combination of therapies in order to see improvement.

Typically CHF is treated with diuretics which help remove the fluid build-up from in the body (usually seen in the lungs or the abdomen), then they add on medications to help with both the strength of contraction of the heart and the frequency of the beating of the heart. Blood pressure medication may also be needed depending on examination and laboratory findings.

Depending on owner finances, and if whole blood taurine or carnitine levels have been tested or not veterinarians may or may not start the dog on additional supplementation. According to research papers that have compiled case study reports – if blood testing isn’t done, or if it is done and values are on the low end of normal supplementation may be started.

Typically dietary change is also discussed, usually diets free of peas, lentils and legumes that have undergone AAFCO feeding trials, and that are grain-inclusive are recommended. This is done because research has found a longer survival time and that many dogs can be taken off medications completely when diet change is included in a treatment plan.

Why is Diet a concern with this new form of DCM in Dogs?

As this is an ongoing investigation by the FDA, cardiologists, nutritionists, and veterinary scientists/researchers – we don’t have all the answers yet. Epidemiological investigations like this are notoriously difficult to figure out, and sometimes they resolve on their own over time without us even knowing the underlying cause.

For example, we still don’t know what caused over 5500 cases of toxicity from Jerky Treats since 2007, and though cases have significantly decreased over time – we still don’t know the cause.

But there are several different published research studies on the association between grain-free diets, dietary change, and this new form of DCM in Dogs. So let’s review some of the research and FDA announcements that have come out thus far – to show what we know, and what we still need to investigate.

What we know is that according to the FDA Report, over 90% of the cases of DCM have been from dogs on grain-free diets that have high in peas, lentils, legumes, and potatoes. And 90% is a very strong correlation.

A round-up review paper published in 2019 evaluated the possibility of legumes/lentils/peas as being a primary cause of DCM in Dogs and found many different areas these ingredients may influence the heart. Through various different mechanisms, legumes/lentils/peas can affect protein digestibility and nutrient absorption. Possible mechanisms were: fiber and bile acid fermentation, deficiency of cofactors for taurine metabolism, digestibility differences in large vs. small breed dogs, mallard reactions, anti-nutrient factors, and more. Researchers brought up an important point that we currently have no research of the inclusion of these ingredients at large portions of the diet (>40%) that many suspect diets are using them.

Digestibility studies done in 2020 on Beagles and Labradors found the Bile Acids produced by grain-free diets were significantly different than grain-inclusive diets. In particular, they found that primary bile acid production was higher than secondary bile acids. As primary bile acids bind-up more taurine than secondary this could influence protein digestibility, leading to deficiency – however since taurine was added in this study – gaps remain in our knowledge.

A further review paper published in 2020 discussed other dietary, medical and lifestyles factors that could influence heart health including: myocarditis from parasitic, viral or bacterial infections; hypothyroidism, toxins including heavy metals, genetics, and dietary: low protein diets, high fiber diets, vitamin b deficiency, copper deficiency, low taurine, metabolism of taurine from methionine and cysteine, carnitine deficiency, the bioavailability of selenium, deficiency of vitamin E.

Many of these factors are being investigated by the FDA currently by analysis of blood samples, saliva samples (genetic testing), typical analysis and toxin analysis of diets, and necropsies that are being performed by the FDA. However more research is needed.

We have several case study papers that have evaluated outcomes of dogs who have switched off a grain-free diet containing “suspected ingredients” to grain-inclusive diets that do not contain said ingredients. Dogs who pursue diet change have longer survival times than those who do not pursue diet change, even those that have later stages of disease such as congestive heart failure.

In an observational study evaluating Golden Retrievers, they found more dogs with early cardiac changes with dogs eating grain-free diets that contain high amounts of peas/lentils/legumes than those eating grain-inclusive diets.

A research study looking at short-term feeding of different pulses – including two different varieties of peas (wrinkled and smooth), lentils, and fava beans showed decreased digestibility of Crude Protein in wrinkled pea diets in comparison to other pulses and a grain-inclusive diet ( 73% vs 84% protein digestibility). Though overall digestibility of diets was good (around 85%).

As this was a short-term study (only 7 days) it has limitations as to long-term effects, and tough taurine levels measured in this study were normal - most boarded nutritionists believe it can take months to years for nutritional deficiencies to take form and present clinical disease.

In the 2021 study done evaluating 4 other dog breeds (Whippet, Golden Retriever, Doberman Pinscher, or Miniature Schnauzer) they found a correlation between early cardiac changes and diets high in lentils, peas, and legumes with diets that were both grain-free and grain-inclusive. Further tying legumes/peas/lentils, and not just “grain-free” diets in general to this new form of DCM in dogs.

Finally, a study in August 2021 analyzed diets that have been highly associated with this new form of DCM in dogs to see how they differ on a biochemical standpoint to grain-inclusive diets that have no known cases of DCM using “Foodomics”. This study cross-referenced ingredients within diets to find peas – not potatoes or lentils – to be highly correlated with differences in biochemical compounds.

You can read a more detailed breakdown of this paper on the blog here.

But even with all this research we still cannot pinpoint exactly what the issue is. We know this is occurring, we know it isn’t the same as previously known forms of DCM in dogs, it’s not hereditary – though we do suspect some breeds or size dogs may be more susceptible to disease. More research still needs to be done in order to fully understand this condition and what we can do to prevent it in the future.

We still need more long-term controlled research studies on this subject with less variability to assess the exact cause of disease. Research of this magnitude would be extremely expensive and take a lot of time to perform. Hopefully, we see studies like these in the future.

We also need better transparency from companies that have had high numbers of cases with researchers - at this time “recipes” have no been released, which forces researchers to infer amounts of ingredients based on ingredient lists - which are easily manipulated for marketing purposes…

How to Avoid diet-associated DCM: What are the current recommendations?

Current recommendations by the FDA are to speak to your veterinarian about your dog’s current medical needs to choose the best diet for them. Some dogs will do best on a grain-free diet, but in other cases, a grain-free diet may not be necessary. Having an open and honest conversation about your pup and their needs is the best way to choose an appropriate option.

There is no current recommendation to supplement taurine to diets OR your dog unless it is medically necessary. As with most things in nutrition – you can have too much of a good thing – though taurine supplementation is Generally Recognized as Safe (GSA) by the FDA – large mega-doses of taurine in a 13-week study in rats did cause neurological signs. And as there are no safety limits currently described in dog foods for minimums or maximum levels – it is important to speak to your veterinarian prior to starting any type of supplementation, especially if the food is already supplemented.

According to boarded nutritionists, the best thing you can do is choose a well-researched diet – especially one that has done extensive feeding trials, with digestibility studies. Also, choose a diet that has been formulated with the help of a board-certified veterinary nutritionist or someone with a phD in animal nutrition. 

Though this isn’t a “guarantee” of perfect health it may help avoid major issues concerning diets as many “suspect” diets have never done any feeding or digestibility studies on dogs.

Personally - due to current research and association of legumes/peas and DCM - I look to avoid these ingredients when I create homemade diets, and I tend to choose premade diet options that do not include these higher on the ingredients list (or at all) if other diets are an option.

If I do choose a diet containing legumes or peas I tend to want extensive research on the diets - including digestibility and feeding trials to provide additional safety information. I don’t think peas or legumes are toxic, but I think there may be a “balancing act” that we need to achieve, and I’m not sure if we have all the information we need in order to make decisions at the inclusion % of peas or legumes in diets at this time.

It’s also important to note that not all dogs seem to present with this condition, thus for certain dogs monitoring for DCM while on a high legume diet may be recommended by your veterinarian.

Additional Resources:

• Questions to Ask Pet Food Company
• DCM & Dogs 2020 Update
• Diet-Associated DCM in Dogs Support Group – Facebook

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