By The Farmer's Dog | July 22, 2020

Every dog person wants to be sure they’re doing all they can to safeguard their dog’s health and well-being. So when news reports that certain kinds of popular diets might be linked to a serious disease called canine dilated cardiomyopathy (DCM) were published, it caused widespread worry and confusion among dog owners.

The topic of diet and heart health is complex, and there’s been ample misinformation circulating around it. While the latest research indicates that there is no definitive link between grain-free diets and DCM, there are many questions that remain unanswered. 

We wanted to provide some clear, useful information on DCM to help all dog lovers make the most informed choices possible about diet and health. 

Why are we talking about DCM and dog diets?

In June 2019, the Food and Drug Administration made headlines when it linked 16 brands of dog food to DCM. 90% of the pet food brands named in the report were considered “grain-free”—they contained no wheat, corn, soy, rice, barley, or other grains—but most did contain, in the words of the report, a “high proportion of peas, lentils, other legume seeds (pulses), and/or potatoes in various forms (whole, flour, protein, etc.) as main ingredients.” 

The report came one year after the FDA issued an alert that it was investigating links between these types of foods and DCM, noting that the disease was showing up in some dogs that aren’t traditionally considered genetically predisposed to it.* The agency called for pet owners and veterinary professionals to report cases of DCM they suspected were linked to diet.

The 2019 report was inconclusive—the agency said it was “continuing to investigate and gather more information” on whether there was any dietary link to DCM at all. But sensational headlines and articles in the wake of the reports glossed over any nuance; they helped sow confusion and fear by delivering the impression that “grain-free food causes DCM” and could be “killing dogs.”

The facts are much more complex. In fact, since the FDA reports, comprehensive new research has been published which has found no definitive link between grain-free diets and DCM.

The new research was conducted by a group of veterinarians, veterinary cardiologists, and animal nutritionists from pet-care research and consulting firm, BSM Partners, who analyzed the results of more than 150 studies on DCM. Taken together, the studies “did not support a link between grain-free and legume-rich diets, and DCM,” according to the lead author of the article, which was published in the Journal of Animal Science.

Researchers noted that the DCM information circulating in the wake of the FDA reports was lacking, They concluded that DCM is a multifactorial medical condition with many causes contributing to the development of the disease. “Therefore, prospective studies investigating, not only diet, but also infection, metabolism, and genetic involvement, must be conducted.”

What we do know about DCM

Dilated cardiomyopathy is a disease whereby the heart muscle in dogs wears thin, and loses its ability to contract normally and pump blood effectively through the body. With the heart muscle not working efficiently, blood backs up in the heart chambers and the organ enlarges in size, resulting in heart failure. It’s a serious condition that can lead to death. DCM is one of the most common heart ailments in dogs; it’s also found in humans and other mammals, including cats. 

Signs of DCM may include rapid or labored breathing when resting, pale gums, coughing or gagging, weakness, lethargy, and collapse or fainting, though dogs may show no signs in earlier stages of the disease. Some dogs may die suddenly from irregular heart rhythm without previous symptoms.

How many dogs are being affected?

Like any dog owner, we think one dog is too many dogs suffering from a serious ailment. It’s important to note, however, that the number of reported cases of DCM is extremely small compared to the number of dogs eating so-called grain-free diets and other forms of commercial pet food (as the FDA itself noted:  “Most dogs in the U.S. have been eating pet food without apparently developing DCM”). And “most” is an understatement. There are about 90 million pet dogs in the United States.  Between January 1, 2014 and April 30, 2019, the FDA received 515 reports of DCM (560 dogs were affected as some of the reporting households had more than one dog); 219 of these cases were reported between December 1, 2018 and April 30, 2019. That’s a vanishingly small percentage of dogs. 

As the authors of the new research in the Journal of Animal Science, state, “based on current literature, the incidence of DCM in the overall dog population is estimated to be between 0.5% and 1.3% in the United States. However, the FDA case numbers (560 dogs) are well below the estimated prevalence. Therefore, it is impossible to draw any definitive conclusions, in these cases, linking specific diets or specific ingredients to DCM.”

Of the 560 DCM cases reported to the FDA, the vast majority, 452, were consuming dry dog food.* Fresh pet foods were not cited in the FDA report. 

The incidence of DCM is also dwarfed by the number of dogs who suffer from diseases like cancer, which occurs in about six million dogs per year, or conditions like obesity (56% of dogs in the U.S. are overweight). 

What causes DCM in dogs

As the FDA states, and as the new research concludes, there is no proven link between a grain-free diet, or any specific diet, and DCM.

According to the American College of Veterinary Internal Medicine, “although there have been many theories as to the cause of DCM, the exact mechanism is still not fully understood.” But while there is no single, scientifically verified cause of the disease, it’s clear that the answer is not as simple as the presence or absence of grain in pets’ diets. 

DCM is a complex problem and available evidence suggests that taurine, food digestibility, and genetics can play a role in the development of the disease. The recent BSM study noted that other causes could include myocarditis, chronic tachycardia, endocrine disease, toxins, and nutritional deficiencies.

The gene factor

Certain breeds, including Doberman Pinschers, Great Danes, Newfoundlands, St. Bernards, and Boxers are more prone to DCM. Some smaller breeds, like Cocker Spaniels are also predisposed. Researchers recently performed genome sequencing on a Doberman family and found that a mutation in a gene called titin, already associated with DCM in humans, was involved with the development disease in these dogs. 

Taurine’s role

A compound called taurine may also play a role in DCM. As ACVIM notes, taurine deficiency can be the cause of DCM when the disease shows up in a dog without a genetic predisposition.

Taurine is one of 20 main amino acids, organic compounds known as the building blocks of our bodies. There’s a high concentration of taurine in certain tissues including the heart muscle. While it’s critical to bodily functioning, taurine is not considered “essential” when it comes to canine dietary standards. This is because, unlike some other amino acids, dogs can produce it themselves if enough of two other sulfur-containing amino acids, methionine and cysteine, are present. 

Natural sources of taurine include fish and shellfish, meat (muscle meat and organs), and dairy products like milk and eggs. Taurine is not found in plants, including both grains and legumes.

The veterinary science community has been studying the connection between taurine and DCM for over 20 years, since before “grain-free” diets became popular. In one early 2000s study,  dogs eating commercial dry diets with lamb and rice were shown to be susceptible to developing DCM. Studies posited that lamb meal didn’t provide adequate methionine and cysteine for taurine synthesis (it’s worth noting that rice, of course, is a grain; and “meals” aren’t made with the kind of muscle or organ meat that’s high in taurine. See below for more on meals).

More recent studies indicate that dogs with DCM show improvement with taurine supplementation and diet change.

As the BSM study authors point out, “further breed-specific studies are warranted, and avoiding nutritional deficiencies is imperative especially in breeds that may need higher concentrations of taurine or L-carnitine, such as cocker spaniels and golden retrievers.”

Food processing

There are indications that a pet food’s protein source, and the way it’s processed may affect amino acids, and how well they can be put to use in the body. Processing protein at extreme heat and subjecting it to the high-pressure extrusion used in kibble manufacturing is thought to reduce the bioavailability of the necessary amino acids.(1) Some researchers have cited high heat used during extrusion as a factor in reducing food’s nutritional value, pointing specifically to a reduction in digestibility of cysteine, which is necessary for the synthesis of taurine.

Things to consider: The Farmer’s Dog point of view

When it comes to DCM, there’s still much to be discovered by veterinary science. Many researchers are calling for more studies of nutrition as it relates to canine heart health, including the impact of food processing. 

Here are a few things we believe dog owners should consider, shaped by the facts, our experience, and the experience of the veterinary professionals we work with. 

Look beyond grain

Again, there’s been no proven link between any diet and DCM. Any claim that “grain-free” foods are the cause of DCM is likely unwarranted. Grains in themselves offer no obvious protection against DCM—they are not a source of taurine, for example. Perhaps more to the point, it’s too simplistic to look at all grain-free foods as one “type” of diet—not all grain-free foods are created equal. 

Protein is key

Consider feeding a diet with a high quality protein, in balance with fresh vegetables and legumes. Ingredients like chickpeas and sweet potatoes provide important nutrients for dogs as long as they are correctly balanced with protein. 

Taurine may be less available in poor-quality protein sources and in foods processed at high heat. Most kibbles start with rendered meals, which are then subject to a high-heat, high-pressure manufacturing process which has been shown to affect the amino acids that help keep dogs healthy. 

What is meal? Meal is a primary ingredient in kibble. It’s a powdered substance that’s made when the protein scraps that can’t be used for human consumption are “rendered,” or processed at extremely high heat to remove moisture and fat. As defined by AAFCO, meal is “the rendered product from mammal tissues, exclusive of any added blood, hair, hoof, horn, hide trimmings, manure, stomach and rumen contents except in such amounts as may occur unavoidably in good processing practices.” “As may occur unavoidably” is a loophole that things that are difficult to remove (like plastic, flea collars, metal, and other substances) can and do end up in the final product. Rendered protein meals are powders that go by the names meat meal, meat and bone meal, poultry meal, poultry byproduct meal and fish meal. Poultry byproduct meal includes “parts of the carcasses of slaughtered poultry such as necks, feet, undeveloped eggs and intestines.” Meat meal is so called because there’s no way to determine if the source was chicken, cow, or any number of the other animals that can end up being rendered. 

Beware of labels

It’s important to know what ingredients, and in what proportion, are in your dog’s food. Many pet food manufacturers can make it difficult for consumers to determine the dominant ingredient in a recipe because of what’s known as “ingredient splitting.” This is the practice of dividing one food type into several separate ingredients (for example: peas may appear as peas, pea protein, and pea flour), so that a meat protein can move into the important first-ingredient slot. You may wish to avoid foods with legumes listed first among ingredients, or multiple kinds of legume products appearing throughout the ingredient list. 

Stay alert

If your dog is showing any of the signs associated with DCM, or if you have any concerns about your dog’s diet, consult your vet. 

A note about fresh food

When it comes to heart health, and the overall, long-term health of your dog, we believe feeding high-quality, minimally processed food is the safest, and best option. 

We use clean, human-grade proteins, vegetables and legumes, which are gently cooked at low temperatures. This means our food retains its nutrients, and your dog can digest, and use those nutrients. All of our recipes are formulated by board-certified veterinary nutritionists to be complete and balanced. Our recipes are made up of at least 50% protein and our supplemental nutrients include taurine. 

We’ll stay on top of the ongoing discussions and research on DCM, and we hope that the discussion generated by the FDA’s reports and the emerging research provide an opportunity for broader awareness of the impact of diet on all areas of our dogs’ health.