In 2018, veterinarians noticed that an increasing number of dogs were showing signs of dilated cardiomyopathy (DCM). This condition occurs when the heart muscles weaken and can’t pump blood as effectively throughout the dog’s body. These dogs didn’t belong to breeds known to be at risk for DCM, but they did seem to have one thing in common—they were eating either grain-free diets or “boutique” diets, often with unusual, grain-free, or legume-rich ingredient lists.
Unexpected DCM Can Be Fatal in Dogs
Oliver was such a dog. At only 3-1/2 years of age, the Golden Retriever owned by Julie Carter, was diagnosed with DCM as well as taurine deficiency, which is often associated with DCM. Oliver’s 9-year-old Golden Retriever housemate, Riley, was also affected. DCM is a serious disease of the heart muscle that can ultimately lead to death. It occurs more often in large breeds, and in some breeds, it’s thought to have a genetic component. It also typically occurs in middle-aged to older dogs. Goldens are not considered an at-risk breed for DCM in general, but they are at risk for taurine deficiency.
Oliver was immediately placed on a mainstream diet containing grain. He received taurine supplements as well as heart medications, remaining symptom-free, until one day, without warning, he suffered a fatal arrhythmia while walking across the kitchen floor. It was August of 2018, just six months after his diagnosis and just five days after celebrating his fourth birthday.
Links Between Grain-Free Diets and DCM
Meanwhile, at Tufts University, Dr. Lisa Freeman, DVM, PhD, DACVIM, a board-certified veterinary nutritionist with a research emphasis on nutritional effects of heart disease, was conferring with other veterinary cardiologists about the emerging link between DCM and grain-free diets. In July 2018, the Food and Drug Administration (FDA), acting on their advice, began an investigation.
From January 2018 through April 2019, the FDA received reports of 553 dogs with DCM, compared with previous years, in which reports received of dogs with DCM ranged from zero to three. These included 95 Goldens, 62 mixed-breed dogs, 47 Labrador Retrievers, 25 Great Danes, and more than 50 additional breeds with more than one report. The FDA found 16 dog food companies that had ten or more cases of DCM associated with their food. More than 90% of the diets were grain-free, and 93% of the diets contained peas or lentils. A far smaller proportion contained potatoes. But when these foods were tested, they contained the same average percentages of protein, fat, taurine, and taurine precursors as products containing grain.
In 2021, Dr. Freeman and fellow researchers published a study comparing diets associated with DCM and diets not associated with DCM. They found that the inclusion of peas not only represented the greatest difference between the two diets, but their results indicated that peas were also associated with higher and lower concentrations of certain compounds compared to the diets not associated with DCM. Right now, the relationship, if any, between these compounds and DCM is unknown. Future research may reveal more information.
Updates on DCM Research
On December 23, 2022, the FDA released its most recent DCM update. Overall, reports of DCM (which had totaled 1382 dogs) have diminished, with only 255 cases having been reported since July 2020. It’s not known whether the decreased amount is because fewer dogs are being affected (most of the diets previously labeled “at fault” have since changed their formulations) or because people have ceased reporting cases as the publicity has worn off.
Unlike primary DCM, which seems to run in certain breeds and has a hereditary component, the cases that are being reported are consistent with secondary DCM, which is associated with nutrition. These diet-associated cases can occur in any breed of dog. In addition, they can sometimes be reversed if caught in time simply by changing the dog’s diet. Unfortunately, the improvement may take a very long time, and sometimes, as with Oliver, dogs that seem to be improving die suddenly.
Are Grain-Free Diets the True Cause of DCM?
Researchers still don’t know exactly what causes it, but they’ve made progress. At first, grain-free diets were blamed, but further investigation revealed some grain-free diets seem to have no ill effects. More often, the affected dogs have been eating commercial grain-free diets that contain pulses (the category of plants that includes peas, lentils, chickpeas, and dry beans). Note that soybeans, a common ingredient in dog food, haven’t been associated with diet-related DCM. In fact, peas are the most-implicated pulse, although this could simply be because they are also the most used. In addition, it’s possible that potatoes and sweet potatoes may be involved, but they were in fewer of the grain-free diets evaluated. All of these pulses and potatoes tend to be included in grain-free diets to substitute for the absent grain.
These peas, pulses, and potatoes aren’t inherently bad for your dog. It takes most dogs a long time, sometimes more than a year, of eating these diets (that is, eating diets containing pulses instead of eating traditional, grain-inclusive diets) before signs of diet-related DCM emerge. However, one study did find that dogs eating a high pea-based diet developed enlargement of their heart’s left ventricle after just three months, although these changes may have been within normal variation. Such changes can occur well before the onset of signs related to heart failure, so it’s possible that many more affected dogs may exist than what has been reported.
New DCM Studies Prove Contradictory
But just when the problem seemed settled, two studies were published in 2023 that seem to have contradictory findings. The first study found that changing from a nontraditional diet (most of which contained pulses and potatoes) to a traditional one improved survival time in 91 dogs (in breeds including American Staffordshire Terriers, Staffordshire Bull Terriers, American Bulldogs, and others of similar type — all breeds not known to be at risk for hereditary DCM) with diet-related DCM. This is consistent with pulses and potatoes being at the core of the problem.
But the second study found that these pulses may not be responsible after all. These researchers found that Siberian Huskies fed diets containing up to 45% whole pulse ingredients and no grains over 20 weeks showed no indications of DCM-like heart issues. Siberian Huskies were chosen because they are not a breed known for hereditary DCM, so DCM could more likely be attributed to diet. At present, it’s unknown if some breeds might be more affected than others when it comes to DCM and diet.
DCM Research Developments: What’s Next?
The AKC Canine Health Foundation (CHF) continues to fund research into this perplexing problem, with CHF-funded studies ongoing at several institutions. The CHF allows dog lovers to participate in or donate to this and other canine health research endeavors. One CHF-funded study has partnered investigators at the University of Florida, Tufts University, the University of Wisconsin-Madison, and the University of California, Davis, to screen for DCM in a large population of dogs with no clinical signs of heart disease, focusing specifically on Whippets, Golden Retrievers, Doberman Pinschers, and Miniature Schnauzers. They are comparing ultrasound findings, plus concentrations of blood biomarkers and taurine, and they’re recording each dog’s diet history. The study began in 2019 and will end in March 2024.
The FDA recently announced it would no longer publish DCM updates unless new information comes to light. That distresses Oliver’s owner, Julie Carter, who has worked tirelessly since Oliver’s death to educate dog owners about the problem. “Unfortunately, because this issue continues to be a contentious one, many dog owners have been misled by incorrect information,” says Carter. “Between the misinformation out there and the lack of public awareness, we continue to identify dogs that have been impacted by this disease daily.” She urges dog owners to not become complacent just because the FDA will no longer be issuing updates about new cases.
Carter does report some good news, however. “After four-and-a-half years of cardiac care, medication, and diet change, Riley, who was also affected by diet-associated DCM along with Oliver, is now fully recovered and about to turn 13 years old!”
How to Guard Your Dog Against DCM
So what can you do to safeguard your dog? First, discuss your individual dog’s diet, as well as any concerns about DCM, with your vet. Dr. Freeman suggests avoiding diets in which pulses are among the ten first ingredients listed first, or that contain multiple pulses. Dr. Klein adds that you should also be sure the label states the food meets the requirements of the American Association of Feed Control Officers (AAFCO) and is a “Complete and Balanced” diet.
If your dog does develop DCM, you may wish to consult with your veterinarian or veterinary cardiologist about changing your dog’s diet. In certain breeds, DCM is considered to have a strong hereditary component, but in others, diet may more likely be the cause. Also, be sure to report it to the FDA so their investigation can continue.
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