For the past three years, Hemopet has been reporting on the U.S. Food and Drug Administration (FDA) investigation into non-hereditary dilated cardiomyopathy (DCM) in dogs. At the end of July 2021, the FDA updated its question and answer webpage regarding DCM. We will be addressing this and provide a response to the FDA’s preliminary conclusions, but we are providing some background first.
What is DCM?
DCM occurs when the heart muscles become weakened and thin, which leads to an enlargement of the heart. With this enlargement of the left ventricular side, valves become leaky and blood pressure increases. DCM can result in death.
What are the signs of DCM?
- collapse or fainting
- coughing or gagging
- decreased appetite
- depressed attitude or quiet and not interactive
- distended belly
- increased effort associated with breathing
- rapid breathing when resting or sleeping
- reduced ability to exercise
- restless sleeping
- weight loss
What causes DCM?
DCM is considered a complex condition that can be multifactorial, which includes genetics, diet, and comorbidities (underlying medical conditions).
What breeds are affected by DCM?
Research thus far suggests a genetic (hereditary) component in several medium and large-size breeds such as Doberman Pinschers, Boxers, Great Danes, Newfoundlands, Irish Wolfhounds, English Cocker Spaniels, and Portuguese Water Dogs. Golden Retrievers and American Cocker Spaniels appear to have breed predispositions to taurine deficiency.
Taurine Deficiency & Other Dietary Contributions to DCM
In dogs, taurine is an amino acid that is synthesized by two other amino acids – methionine and cysteine – primarily in the liver. Our previous posts about DCM primarily focused on taurine deficiency, which has a strong link to contributing to DCM development in several breeds of dogs and has been researched heavily. For instance, larger dogs are possibly less likely to synthesize taurine as well as smaller breeds.
Of course, other factors such as carnitine, oligosaccharides, and the amount of dietary fiber might come into play.
What is the FDA investigating?
To quote the FDA:
Historically, DCM has been primarily linked to a genetic predisposition in certain breeds, but emerging science appears to indicate that non-hereditary forms of DCM occur in dogs as a complex medical condition that may be affected by the interplay of multiple factors such as genetics, underlying medical conditions, and diet. Aspects of diet that may interact with genetics and underlying medical conditions may include nutritional makeup of the ingredients and how dogs digest them, ingredient sourcing, processing, formulation, and/or feeding practices.
The FDA’s Preliminary Conclusions
To quote the FDA:
Most of the diets associated with the reports of non-hereditary DCM have legume seed ingredients, also called “pulses” (e.g., peas, lentils, etc.), high in their ingredient lists (although soy is a legume, we did not see a signal associated with this ingredient). These include both “grain-free” and grain-containing formulations. Legumes, including pulse ingredients, have been used in pet foods for many years, with no evidence to indicate they are inherently dangerous, but analysis of data reported to CVM indicates that pulse ingredients are used in many “grain-free” diets in greater proportion than in most grain-containing formulas. FDA has asked pet food manufacturers to provide diet formulations so we can further understand the proportions of ingredients in commercially-available diets and possible relationships with non-hereditary DCM.
FDA has received reports of non-hereditary DCM associated with both grain-free and grain-containing diets. Most of the diets associated with reports of non-hereditary DCM have non-soy legumes and pulses (e.g., peas, lentils, etc.) high in their ingredient lists. CVM’s data show that pulse ingredients are likely used in many “grain-free” diets in greater proportion than in most grain-containing formulas.
The FDA receives incident reports concerning product safety concerns regarding marketed human drug and biologics, human or animal reportable foods, animal drugs, animal foods, tobacco products and dietary supplements. The U.S. Department of Agriculture receives incident reports about animal vaccines.
The FDA collected over 1,100 incident reports of DCM in dogs. (Ryan Yamka, PhD, points out that at first the agency only put out a call for dogs eating grain-free foods.)
The agency then narrowed it down to a subset of 150 clinical cases that it tracked and continues to track. This narrowing process is completely normal, tedious, necessary and time-consuming. The biggest limitation with this sort of tracking is losing subjects to follow-up. For instance, companion dog parents may not respond to emails or voice messages.
After reviewing a presentation the FDA gave at Kansas State University’s Scientific Forum Exploring Causes of Dilated Cardiomyopathy in Dogs on September 29, 2020, it appears the FDA was only given incomplete case history – either prior to diagnose and after case resolution – in only about eight cases regarding diet.
Honestly, that is impressive.
Another big limitation to clinical tracking is having a preponderous of evidence weighted heavily to one side, but that methodology lacks a control group for comparison.
A third limitation – particularly when it comes to veterinary care – is that it is expensive and many companion pet parents do not have veterinary care insurance. The FDA wanted dogs that had at least two echocardiograms to determine recovery status.
It is important to remember that the FDA is simply following the clinical outcomes and interventions of the incident reports. It does not provide medical guidance at this stage.
What did the FDA’s presentation report? We encourage our readers to read it and follow along with the questions and points we have.
For some background, the FDA split the reports into two groups based on when they were received. Group One reports included 121 dogs diagnosed with DCM between January 2018 and April 2019. Group Two’s were between November 2019 and July 2020. We will primarily focus our questions on Group One Fully Recovered since the FDA acknowledged that Group Two’s data was preliminary at the time of the presentation.
#1. Page 6: The FDA reported that 23 dogs were fully recovered, 84 had partially recovered, and 11 dogs had no recovery. Sadly, 7 dogs died.
Did the dogs pass away from DCM or another disease? Were they euthanized? Were necropsies performed?
#2. Page 8: The FDA provided Group One’s partially and fully recovered dogs by breed. Golden Retrievers were abundantly represented in both segments.
Why include a breed that may have a genetic predisposition for taurine deficiency as part of a group of dogs who are being defined as having non-hereditary DCM? The FDA even acknowledged this possible link in its June 27, 2019 update titled, “FDA Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy.”
Furthermore, why include Doberman Pinschers, American Cocker Spaniels, or any breed for that matter that may have hereditary DCM?
Lastly, mixed breeds were also abundantly represented. What were the mixes? Golden Retriever mixes (i.e. Goldendoodle) are very popular these days. Were any of these dogs a Golden mix or another mix with a breed known for having hereditary DCM?
#3. Page 9: If the inclusion criterion to be included in either Group One or Group Two was two echocardiograms, why not a blood taurine test as well?
In Group One Fully Recovered, 16 out of 23 dogs were tested for taurine status. 10 of those dogs had low taurine. Out of the four comorbidities – congestive heart failure, arrhythmia, valvular changes, and low taurine status – the last was the most commonly reported.
What breeds had low taurine?
Finally, why was obesity or malnourished (underweight) not included as a comorbidity? Were any dogs considered obese or malnourished?
#4. Page 11 regarding Group One Fully Recovered states: “All dogs that fully recovered received a diet change. Nearly all dogs were also treated with taurine and pimobendan. Over half of the dogs also received an ACE inhibitor, whereas additional treatments and supplements varied.” The other treatments included furosemide (Lasix, water pill), L-carnitine, unspecified antimicrobials, doxycycline (antibiotic), and omega-3 fatty acids.
What were the medical effects of the additional treatment options?
#5. Reverting back to page 10 which states regarding Group One Fully Recovered: “Allergy or atopy followed by gastrointestinal disease (i.e., sensitive stomach/irritable bowel disease) was the most frequently reported historical comorbidity. The diets reported to us for these dogs contain novel and/or limited ingredients and are likely fed to the dogs to help nutritionally manage allergies, atopy, and gastrointestinal diseases. There were only two dogs in each of the other categories.”
Did any of the dogs that had dietary changes have a resurgence of atopy, allergy or gastrointestinal issues?
#6. Page 14: The FDA noted that blood taurine values did not correlate to how large the left ventricle was at diagnosis. However, the agency also noted that dogs with severely low taurine values had left ventricles that shrank more than dogs with taurine values near, within, or above the reference range.
#7. Skipping ahead to pages 23-26. The FDA points out that 93% of the Group One Partially and Fully Recovered cases ate grain-free foods before recovery, 0% of cases were exposed to meat or poultry byproducts prior to recovery, and that 94% of reported products contained peas and/or lentils in their top ingredients. The FDA report does not mention organ meats that may be used in grain-free diets.
For Group One Fully Recovered, 96% of the reported recovery diets were grain-containing.
Those statistics are impressive and would cause anyone to decide to switch their dog’s diet.
DCM is a very serious disease. Yes; we want the best course of action for recovery.
We find it concerning, though, that all of the dogs were given the same protocol of being placed on grain diets with or without additional medical interventions. Additionally, we find it concerning that 93% of the dogs selected were on grain-free diets prior to change. That’s seems biased.
At the end of the day, we still do not know what medical and dietary intervention combination worked best.
Additionally, we believe the FDA should let us know where these cases came from. The FDA fully admits that it is working closely with three veterinary researchers and a veterinary cardiology clinic.
Two of the researchers are humble, quiet and sticking to the research they continue to conduct.
Unfortunately, another has sensationalized the situation, received research funding from four major pet food manufacturers, has a keen way of making snappy cliché sound bytes that are picked up by the media, and has blasted grain-free and novel protein pet food.
We see confirmation bias.
We completely understand that the FDA is trying to receive the most complete information possible. We also have read over some of the submitted incident reports. While many of the reports are heart-wrenching, many of them do not give the FDA enough information. Indeed, these incident reports may be too emotional and not as clinically needed to make an unbiased determination.
Inevitably, the sensationalism and the select few skewed the evidence.
Since the heightened awareness of DCM in dogs around June 2018, small and large pet food manufacturers have sponsored research into the causes of DCM. It is unfortunate that veterinary research has to be funded by interested parties, but that is the way of the pet world.
We will say that much of the research is unbiased, excellent and breakthrough. We are particularly impressed with the amino acid oxidation research that is determining if dogs of different breeds and different sizes have different amino acid requirements.
Unfortunately, this new research and prior excellent research has largely been ignored.
If you are worried about your companion dog, we suggest you discuss it with your veterinarian, have all of the necessary tests run and make the best determination as to how to move forward with your companion dog’s nutritional needs.
Ryan Yamka, PhD.
Dr. Dodds and Hemopet encourage everyone to read Ryan Yamka’s informative post titled, “DCM and grain-free pet foods: 3 strikes and you’re out!” on Pet Food Industry.