Is grain-free the route to a broken heart?
Over the past couple of years, there has been a significant increase in the diagnosis of broken hearts, more specifically, dilated cardiomyopathy (DCM) in dogs. What sparked interest and subsequent further investigation was that this form of heart disease was being identified in dog breeds not commonly affected by this condition.
DCM is typically a disease affecting large or giant dog breeds, such as Dobermann pinschers, Great Danes, Irish wolfhounds, and boxers.
But instead, it was breeds such as whippets, Shih Tzus, and bulldogs that were presented to veterinary clinics with changes consistent with a diagnosis of DCM.
So, what sparked this pandemic of broken hearts?
Over this same time period, feeding grain-free diets and other boutique and exotic varieties also became increasingly popular, prompting much research and a lot of comments on the safety around feeding such diets, and, trying to find the underlying cause or link between the two.
Spoiler alert: It’s still an active area of research, so there are still some questions to be answered. However, we will discuss diet-associated DCM in more detail and delve into some possible mechanisms behind this new-ish phenomenon.
Some definitions to start:
Let’s start off with some definitions or at least brief explanations of some of the terms we will be using.
Dilated cardiomyopathy (DCM) – this is a relatively common acquired heart disease in dogs. DCM is a disease process involving the heart muscle, where the muscle becomes weak and loses its ability to contract normally.
Types of DCM – the most common type of DCM is classified as primary or hereditary and has been linked to genetic mutations in certain dog breeds.
Nutritional deficiency has also been identified as a cause of DCM, specifically taurine deficiency (which can be the case with vegetarian diets), and rarely, L-carnitine and vitamin E. Other (uncommon) causes include toxins (for instance, heavy metals) and infectious organisms. Then there is the topic for today – diet-associated DCM.
Grains – what are grains; it might seem like a simple question, but for the purposes of this discussion, it is worth defining this a bit better. Basically, we're looking at foods made from wheat, rice, oats, cornmeal, barley, or another cereal grain - these are considered grains or grain products.
Is there a link between grain-free diets and DCM?
As mentioned before, identifying DCM in unusual breeds such as Labrador retrievers, whippets, miniature schnauzers, Shih Tzus, and bulldogs that were being fed grain-free, legume-rich diets was the first clue to a possible link between these diets and DCM development.
A further clue came in the form of improvement in heart function and size following dietary change – something that is not seen with primary cases of DCM.
Is it just grain-free diets to blame?
Nope. Diet-associated DCM has been associated with both grain-free and grain-containing diets. It’s probably more appropriate to refer to the culprit diets as non-traditional diets. What this means is that they contain pulses and, to a lesser extent, tubers such as potatoes or sweet potatoes.
What are these pulses that are often mentioned when it comes to an underlying cause for the association?
Pulses include peas, lentils, chickpeas, and dry beans.
They are part of the legume family, but that doesn’t mean that all legumes are to blame. For example, soy is also a legume but has not been associated with the development of diet-associated DCM.
Peas have been proposed as being the most commonly associated ingredient with this form of DCM, however, it could simply be that they are the most commonly used ingredient from the legume family.
So, does that mean that any diet containing peas or other pulses is potentially harmful?
In short, no. Such ingredients have been used in pet food products for decades and haven’t appeared to cause problems like this until recently. So why now, then? With the trend to feed grain-free diets a few years back, this created a sort of gap that needed to be filled when it came to formulating diets, and pulses were some of the ingredients that were being reached for and incorporated, likely in higher amounts and proportions than was previously the case.
It is also important to recognise that not every dog eating a non-traditional diet will develop heart disease. That being said, feeding such diets might increase the risk of developing diet-associated DCM.
What are the potential mechanisms behind this association between feeding non-traditional diets and the development of diet-associated DCM?
Unfortunately, this remains to be determined.
Given the association between taurine deficiency and DCM in both dogs and cats in the past, this was initially suspected to be part of the problem. However, this theory was largely debunked by demonstrating normal taurine concentrations in affected dogs using blood assays of taurine.
So, if it’s not taurine, then what is the link?
Various hypotheses have been put forward, one of the more popular ones being that compounds in these ingredients (e.g., pulses, and tubers) may have toxic effects on the heart.
What these compounds might be is an area of ongoing research – watch this space!
Is it just dogs that are negatively impacted by non-traditional diets?
No, although most of the media attention has focused on the potential effects on dogs. There have been reports of more than 20 cases of cats with suspected diet-associated DCM. These were in cats fed high-pulse diets, typically for long periods of time. While cats can be affected, diet-associated DCM does appear to predominantly be a dog problem.
Take-home message:
There is an association between the feeding of high-pulse diets and the development of diet-associated DCM in dogs and a small number of cats. Not all pets eating these diets will develop diet-associated DCM, however, feeding such diets may increase the risk of this type of heart disease developing.
So, what should you do?
It is important to review a product's list of ingredients—if pulses (e.g., peas or lentils) are listed in the top ten ingredients or multiple pulses are present, the proportion of pulses might be problematic, and, if possible, such diets should be avoided.
Consider changing to a diet that contains grains.
It is also worth mentioning that feeding such diets does not immediately lead to the development of diet-associated DCM.
Although, a recent study demonstrated changes consistent with DCM, albeit subclinical, in dogs fed a wrinkled pea diet after only four weeks.
Why is this important? Well, most reports of diet-associated DCM are of pets fed the diet for long periods, often over a year.
This recent finding would support discontinuing a non-traditional or pulse-based diet as soon as possible, because even if the pet in question does not have any clinical signs, it might be the case that they do have changes consistent with DCM.
Consider chatting with your local veterinarian about organising a heart ultrasound (echocardiogram) if your dog or cat has been on a non-traditional diet for basically any length of time.
Lastly, if you have a dog that is considered an ‘at-risk’ breed for taurine deficiency (these include American Cocker Spaniels, Golden Retrievers, Newfoundlands, and Dalmatians) and you are feeding them a non-traditional diet, it is strongly advised to assess taurine status, have a heart ultrasound done, and consider changing the diet.
If you have any questions on the topic, please feel free to get in touch with us at info@vngpets.com
Resources:
American Animal Hospital Association – Diet-associated Dilated Cardiomyopathy:
Petfoodology - Diet-associated dilated cardiomyopathy: The cause is not yet known but it hasn’t gone away:
U.S. Food & Drug Administration - FDA Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy:
Veterinary Partner (Veterinary Information Network) – Diets and Heart Disease in Dogs and Cats:
Veterinary Partner (Veterinary Information Network) – Dilated Cardiomyopathy in Dogs and Cats:
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