Friday, February 19, 2021

New Diet-Associated DCM Study: Feb 2021

     Another retrospective study (Walker et al. 2021) concerning dilated cardiomyopathy in dogs was made available for pre-proof access, meaning that the article has been peer-reviewed and accepted for publication, but will undergo some further editing/formatting for final display in the journal. This research, published in the Journal of Veterinary Cardiology, can be accessed with a subscription or single purchase, but is otherwise not available to the general public. 

    The study itself is somewhat similar to the paper published in December (Freid et al. 2020). It is a retrospective analysis of dogs diagnosed with DCM and CHF (congestive heart failure) at NC State University College of Veterinary Medicine between 1/1/2015 and 07/10/2019. Dogs were excluded if their diet history was unknown. The analysis divided dogs into two groups based on whether their diet was grain-free (GF) or grain-inclusive (GI) at the time of diagnosis. Dogs eating GF at the time of diagnosis were switched to GI as part of the treatment. They're therefore referred to as pGF (prior grain-free). The authors further divided the pGF group based on the length of time a GF diet had been consumed (6 months - 2 years, 2-3 years, and 3+ years). 

    The findings of this study are consistent with previous research, providing further evidence that grain-free diets are associated with a lower mortality, reversible form of DCM, which in turn is associated with improved outcomes following diagnosis. This study does not provide insight to the exact etiology of this observation, but reinforces the need for continued investigation. The authors acknowledge several limitations, including small sample size, and encourage further research. 

Summary of Data:

  • 67 dogs met the inclusion criteria, 43 eating GF and 24 eating GI. 
    • 23 breeds were represented, 19 in the GF group and 11 in the GI group
      • Great Danes, Dobermans, and Labrador Retrievers were most represented in both groups, 18/43 (42%) in GF and 16/24 (67%) in GI. 
    • Age varied significantly between groups, with GF median age of 6 years and GI median age of 9 years
  • 21/43 (49%) GF dogs died and 19/24 (79%) GI dogs died during the study period. 
    • The effect of diet on survival was not statistically significant when considered overall
  • Survival was also assessed in the context of dogs that lived at least 8 days following initial diagnosis, to consider the impact of treatment therapy on dogs that lived to undergo it.
    • For these dogs, previous diet was significantly associated with survival, with pGF dogs that switched diet having better outcomes than dogs eating GI at time of diagnosis
      • Within this group of dogs that survived at least one week, median survival time was 465 days for pGF and 263 days for GI. 
      • Consuming GF diet for a longer time prior to diagnosis was associated with greater mortality (risk of death).
  • On average, pGF dogs reduced medication doses over time while GI dogs increased or maintained medication doses over time. 
  • There was a significantly greater decrease in LVIDdN (diameter of the left ventricle of the heart) over time in the twenty six pGF dogs re-evaluated when compared to the seven GI dogs re-evaluated. 

Additional Resources

Published Research


DCM Resources / Reading

    Sub-group for Veterinary Professionals


General Pet Nutrition Resources / Reading

WSAVA: FAQ, Guide to Nutrition on the Internet (Dogs) (Cats)

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Saturday, February 13, 2021

Diet-Associated / Non-Hereditary DCM Q&A (2021)

 


   This question list is compiled based on common objections/questions surrounding the FDA's investigation into DCM in atypical breeds in association with grain-free/high-pulse diets. The information provided comes from my personal knowledge background as a veterinary student, conversations I have had with cardiologists, nutritionists, and veterinarians close to the subject, public interviews or statements from experts, and published academic literature on the topic, the latter two linked where referenced or at the end. If you have any questions or input, please use the contact form to the right, the comment section of the post, or email info@docofalltrades.net 

This is intended to be educational only. If you have questions or concerns about your pet's health, please contact your veterinarian to schedule an examination. 

Use the table of contents below to jump to a specific topic. You can also share this Q+A via the weblink or on Facebook. You can copy the link url from any of the questions below to link someone directly to that specific part of the Q&A. 


Conflicts of Interest

    It's a common misconception that "this was all incited by a nutritionist trying to defend the waning sales of big pet food companies as grain-free diets skyrocketed." No part of this claim actually follows. This investigation was announced to the public in 2018, but cardiologists had been in contact with the FDA for several years prior to discuss atypical cases of DCM that they were diagnosing, with an apparent common factor in diet. The incitement of this investigation was discussed in The Washington Post and New York Times. Each story provides some insight into the various cases cardiologists across the USA were seeing that prompted contact with the FDA. 

    The confusion with the involvement of nutritionists likely comes from a commentary published in JAVMA co-authored by Dr. Lisa Freeman, a veterinary nutritionist, and several colleagues. This commentary was published after the FDA's public announcement and was intended to review historical knowledge of diet-associated DCM and recap the (limited) information we had so far on the emerging issue being investigated by the FDA. In addition, it sought to alert veterinary professionals to a potential issue and encourage vigilance. In no way did this piece broadly condemn certain diets as an absolute cause for the issues being seen. The summary read (emphasis added): 

"Pet food marketing has outpaced the science, and owners are not always making healthy, science-based decisions even though they want to do the best for their pets. The recent cases of possible diet-associated DCM are obviously concerning and warrant vigilance within the veterinary and research communities. Importantly, although there appears to be an association between DCM and feeding BEG, vegetarian, vegan, or home-prepared diets in dogs, a cause-and-effect relationship has not been proven, and other factors may be equally or more important. Assessing diet history in all patients can help to identify diet-related cardiac diseases as early as possible and can help identify the cause and, potentially, best treatment for diet-associated DCM in dogs."

    This was published in 2018, and now in the face of continued caseloads and emerging findings, researchers still, in some cases even more strongly than ever, believe that there is a strong risk factor for the development of DCM secondary to certain diets. However, it is clear that this 2018 piece in no way claimed any kind of certainty. 

    Dr. Freeman does have several disclosures listed. This is not unusual. As a nutritionist, her job inherently involves working with the manufacturers of pet foods to ensure quality and safety for companion animals. As a specialist and as someone in academia, she is sought for speaking engagements. Disclosure of potential conflicts is an ethical standard in scientific publications, and is considered an act of transparency. Previously speaking for a company or receiving a research donation from them does not mean that one is beholden to that company to defend or exonerate them. While disclosures should always be reviewed and considered in their context as a source of potential bias, and while sometimes that bias reveals itself, such real or perceived conflicts do not inherently invalidate research or commentary. 

    Even still, several major brands manufacture and sell grain-free diets (such as Purina and Hill's). These major brands also have not experienced catastrophic loss of market share to boutique brands. The insinuation that they would feel so threatened by smaller manufacturers that they would craft an elaborate conspiracy involving a federal agency investigation into the death and illness of dogs rather than just shifting course on their own marketing strategies is, for lack of a better word, absurd. 

    Unfortunately, this issue has not been free from the influence of politics, industry, or bias. Pet food is a huge, profitable industry, and so is pulse legume farming. Some aspects of both industries have been threatened by the investigation at hand, in the loss of grain-free sales as reported by Pet Food Industry, and the subsequent estimated loss of pulse legume profits. Pulse grower associations have donated funds to research that they believe will vindicate their crops. Highly implicated brands have invested in disinformation campaigns downplaying this issue. A group of senators wrote to the FDA about being careful of the impact of their words, noting that the investigation was of significant interest to several groups of people, including farmers in their states. 

    Dr. Solomon, Director of the FDA's Center for Veterinary Medicine, has acknowledged the need to tread carefully in the face of this pushback: "Although CVM’s investigation must be driven by science and our public health mission, we are acutely aware that promoting transparency and public awareness may not be kind to everyone’s bottom line."

    It's very telling that within the two 'camps' of thought ('yes diet is an issue' vs 'no this is blown out of proportion'), the loudest objections are coming from those directly involved in the industry as it pertains to the formulation and sale of non-traditional diets. We shouldn't ignore that some profits are hurting, but ultimately investigation must be driven by good faith desires to understand the underlying issue in the interest of companion animal health and welfare, even if that means some businesses may be harmed. 

The FDA's Most Recent Update

    The FDA's most recent update reaffirmed that diet remains a potential factor, despite multiple industry news outlets claiming otherwise. VIN News Service has contacted the FDA directly to clarify this. The actual update from the FDA can be accessed by the public, as well as a new Q+A on their investigation. Excerpts include (emphasis added): 
  • "If there is one point I want to drive home, it’s that the best thing you as a pet owner can do is to talk to your veterinarian about your dog’s dietary needs based on their health and medical history."
  • "Our veterinarians, animal nutritionists, epidemiologists and pathologists have been working with veterinary cardiologists and nutritionists from academia, industry and private practice to better understand the clinical presentation of the cases and potential ties to diet, such as bioavailability of critical nutrients and how well a dog digests these nutrients."
  • "As we look further into the role that diet may play in these cases, we hope to explore additional avenues of inquiry such as formulation, nutrient bioavailability, ingredient sourcing, and diet processing to determine if there are any common factors."

    Less than a year ago, a headline began to circulate that '150+ studies find no link between diet and DCM.' The problem: most of those studies were not looking for or evaluating such a link! Of the 150+ cited sources, only FOUR are actual studies on the current issue of DCM and grain-free/legume-rich/non-traditional/BEG diets. Two are literature reviews on the current issue. Three represent different iterations of the FDA investigation. Only a handful more pertain to (different types of) diet-associated DCM at all. The majority are on other forms of DCM, and a handful don't pertain to DCM and dogs at all. 
    This literature review has been widely criticized by veterinarians, including cardiologists in a VIN News piece and by 'SkeptVet' Dr. Brennan McKenzie in a piece for Veterinary Practice News. Emily Brill with The Canine Review also investigated and reported on the underlying conflicts and controversy surrounding this literature review. 
    To summarize a few issues: Study authors omitted discussion on the significance of observed reversal of DCM in dogs following diet change. They mischaracterized the need for medical recommendations in the presence of clinical observations, regardless of the status of ongoing research. The study authors disclosed no conflict of interest, despite that four of the five work for the consulting group that formulates for Zignature, the second-most frequently named brand in the FDA update. One is even named as Zignature’s veterinarian on staff. The conclusions claim that there is no association between DCM and diet, despite the fact that correlation very much presents itself as a 'link.' Ultimately, the literature review is a misleading opinion piece that discussed mostly unrelated literature to come to an unjustified conclusion that leaves pet owners and other interested parties less informed than they would otherwise be. 

Genetic DCM, Predisposed Breeds

    DCM most commonly occurs in two specific breeds: Doberman Pinschers and Great Danes. A few other breeds are classically considered predisposed as well; Portuguese Water Dogs experience a specific and unique juvenile form of the disease. Boxers are prone to 'Boxer Cardiomyopathy,' medically known as Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC). This disease can mimic the appearance DCM or occur simultaneously with it. At least one family of Dalmatians have been documented to experience low-protein diet-associated DCM. Taurine-deficient DCM has been documented in a family of Golden Retrievers. Cocker Spaniels have also been associated with taurine-deficient DCM. In general, larger and giant breed dogs are more likely to experience DCM than smaller breed dogs, which are more likely to experience mitral valve heart disease. DCM is the 'second most common cardiomyopathy in dogs," but still only represents about 10%. Mitral valve disease represents a whopping ~75% of canine heart disease in the US. 
    DCM is more common in certain breeds, and genetic markers have been identified for some breeds, but it is not exclusively a genetic disease. DCM can be 'primary' (directly related to the heart, as in genetic conditions that certain breeds are predisposed to) or 'secondary'(directly related to something other than the heart, such as a toxin, an infectious disease, a nutrient deficiency, or an endocrine disease). 
    Primary DCM is a progressive condition that can be improved and slowed with medications, but cannot be reversed in the sense that the dog can be weaned off of medications and return to normal cardiovascular function. However, secondary DCM can sometimes be reversed and 'cured,' such that medications can be discontinued and heart parameters can return to normal, or almost normal, values. This usually requires that the underlying cause be addressed before irreversible damage has been done to the heart tissues. Double board certified specialist Dr. Sherry Sanderson, Internist and Nutritionist, has discussed primary vs secondary DCM in a podcast interview with Down With Dogs. 
    
    To bring this all around to the FDA's investigation, there are two important considerations: That the entire investigation began due to cardiologists sounding the alarm over non-predisposed breeds presenting with DCM, and dogs predisposed to primary DCM can also develop secondary DCM. The two conditions are not mutually exclusive. In fact, the FDA has discussed recovery seen in two Dobermans that saw reversal of their disease process upon switching diet. These dogs may still develop and succumb to primary DCM. But that they improved with a therapy change suggests that they had a secondary form of the disease. Geneticist and Veterinary Cardiologist Dr. Joshua Stern has discussed genetic DCM in the context of diet-associated DCM cases in several webinars. While these were not recorded for public access, Dr. Stern is continuing to research diet-associated DCM and still does not believe genetics to be the primary underlying cause for these cases. 

    The FDA 2019 data includes 59 classically predisposed dogs (Doberman, Dane, Boxer, and Mastiff), 95 Golden Retrievers (which are not predisposed to heart disease but may be more susceptible to nutritionally-mediated DCM), 75 mixed or unknown breeds, 86 large breed dogs (Labrador Retriever, German Shepherd, German Shorthaired Pointer, Weimaraner, Standard Poodle), and 59 medium or small breed dogs (Pit bull, Aussie, Sheltie, American Bulldog, Bulldog, and Shih Tzu). Dogs as young as five months and dogs as old as 16 years have been reported. Dogs as small as 4 pounds and as large as 212 pounds have been reported. All breeds, ages, and sizes are represented. This is not likely to be attributable to an underlying genetic condition. The FDA has dubbed these cases "non-hereditary DCM." DCM is sometimes a genetic disease, but these cases under investigation do not appear to be genetic in origin. 

    There are a number of other factors that have been discussed and investigated as a potential underlying cause. The potential for other factors has not been ignored. However, diet remains the single most common denominator among reported cases. This is along with a disproportionately high number of cases from diets with relatively low market shares. This trend would not be expected from chance. It also would not be expected if the underlying cause were something like vaccines, flea and tick medications, or environmental pesticides-- these factors would impact the general dog population as a whole, and we would expect reported cases to mimic market trends in terms of diet being consumed. Additionally, a trend would likely emerge, and be noticed by clinicians, where dogs presenting with illness were recently vaccinated with a specific vaccine, recently put on a specific flea medication, or recently exposed to a new yard pesticide. Instead, what clinicians have observed is a trend with a specific diet type-- grain-free or legume-rich. 

    Other known causes of DCM include tick-borne illness and severe unmanaged hypothyroidism. In the 2019 update provided by FDA's Vet-LIRN, they reported that 18 dogs had a history of hypothyroidism and 17 dogs had a tick-borne disease. These causes are being explored, but are not turning up answers. In the Kansas State Forum presentation, the FDA showed a diagram comparing the geographic distribution of tick-borne illness and of the reported cases. This comparison did not suggest a strong correlation with regions of high tick-borne disease levels.  




Researchers continue to investigate a variety of potential causes. Up to this point, diet remains the most consistently identified common factor. 

Complexity of Factors

    The FDA has stated that "DCM is a complex medical condition that may be affected by the interplay of multiple factors such as genetics, underlying medical conditions, and diet." This statement, while true, also applies to virtually anything in medicine. Biological systems are complex, and it may be centuries before we fully understand all the nuance underlying them. However, that does not preclude recognizing avoidable factors that cause a substantial increase in lifetime risk of certain diseases. Cancer is a complex umbrella of medical conditions that are affected by the interplay of many factors, including genetics, diet, and environment. Despite the complexity of these processes, we still acknowledge risk factors, such as exposure to carcinogenic compounds.  
    Since many of the dogs that recover are on medications, doesn't that mean diet change has nothing to do with improvement? It's a common question, and one with a very simple answer: cardiac medications improve function and treat heart disease, to reduce symptoms, slow the progression of disease, increase patient comfort, and extend patient life, but they do not cure heart disease. What that means is that typically, a dog started on cardiac medications will be on those medications for life and will experience some degree of disease progression over time, even if they show initial improvements secondary to medication administration. However, what is being seen in dogs that switch diets and start cardiac meds is substantial improvement up to complete reversal of heart disease. Additionally, some of these dogs are able to wean off of their cardiac medications and return to being clinically normal. This is not typically seen with heart disease, and there are very many dogs that receive these medications as part of routine therapy for heart disease. The only apparent explanation is change of diet. In previously documented nutritional DCM cases, diet and nutritional supplementation alone was shown to be sufficient for curative reversal of the disease. 

    To go more in depth... Administration of pimobendan has not resulted in complete discontinuation of medical therapy for CHF in any published clinical trials. The outcomes of dogs on pimobendan in clinical trials do not suggest that DCM improves to such a degree that medical therapy will be stopped or echocardiographic measures will normalize. Reduction of echocardiographic measurements is not the same as a complete resolution of clinical signs and echocardiographic evidence of cardiomyopathy, the latter of which is being reported in the cases in question. Pimobendan does not “cure” DCM, and yet dogs in cases reported to the FDA are showing a complete recovery from the disease. It is unlikely attributable to the administration of pimobendan as a primary factor. 

    Taurine is, generally speaking, documented to produce a positive inotropic effect, but it isn’t considered standard of care for DCM of genetic origin. There is no data that documents such a significant positive inotropic response in dogs with DCM supplemented with taurine alone, in the absence of a taurine deficiency. While taurine may improve some parameters, and dogs with DCM may benefit clinically from administration, much like pimobendan, it does not “cure” DCM (unless the DCM is secondary to taurine deficiency).

    To pull this all together… administration of medical therapies like pimobendan and taurine alongside a diet change can be confounding variables, but they also appear to be unlikely contenders for standing alone as explanations for the observed disease resolution. The presence of these variables does not invalidate or undermine the importance of the role of diet in the etiology of this disease. Providing the best medical care for these animals is the ethical responsibility of a clinician, even if that reduces the research value of case evaluations. 

Looking For A Cause & Past Examples

    The FDA made the public aware of this investigation in 2018, and now in 2021 we still have many more questions than answers. Even research done independently from the FDA has not offered a clear underlying cause and mechanism. This is understandably frustrating to pet owners, and truly, any member of the public or industry without a background in research. The unfortunate reality is that these things take time, especially with limited funding or ethical concerns. For example, doing clinical trials on dogs to determine if certain diets induce heart disease would entail trying to induce heart disease in said dogs. When using client-owned animals for prospective studies, it can be difficult to control variables without compromising patient care (for example, withholding taurine supplements or heart medications or not recommending a diet change). It is unsurprising, albeit frustrating, that we don't have a definitive answer yet-- and the truth is, we may never have the rock-solid, air-tight 'proof' that some are looking for. Most recently (August 2021) researchers may have identified several avenues for future research to hone in on a specific cause and mechanism. 

To best illustrate how this compares to other situations, we can look to the (ongoing) 2007 FDA Jerky Investigation, the long-known but poorly-understood association between grapes and canine renal failure, and finally, the link between tobacco and lung cancer. 

    In 2007, the FDA began receiving and collecting reports of illness associated with jerky treats marketed for pets. Between 2007 and the end of 2015, they collected over 5000 complaints involving over 6000 dogs, over 1000 of them deaths. A variety of adverse events have been reported, including GI distress, elevation of liver enzymes, and renal or urinary dysfunction. Most striking has been 'Fanconi-like syndrome' or FLS, a loss of certain nutrients in the urine that is typically seen only in specific breeds with a genetic predisposition, such as basenjis. Removal of the jerky treats from the pets diet has resulted in improvement alongside appropriate medical treatment. 
    The FDA has tested these treats and to this day has not uncovered an underlying cause for these observations. They have tested for bacteria, metal contaminants, irradiation, pesticides, antibiotics, antivirals, mold and related toxins, rodenticides, known kidney toxins such as melamine, and a variety of other toxins. 
    The FDA has explained some of their challenges in undercovering an underlying cause to these cases:
  • "In human illness outbreaks caused by foodborne bacteria or contaminants, FDA works in concert with the Centers for Disease Control and Prevention (CDC) and state boards of health, which collect and track cases of foodborne illness. Unfortunately, there is no equivalent for pets, which means that it is difficult to accurately evaluate the scope of an outbreak."
  •  "Very little is known about the possible causes for non-genetically related (acquired) Fanconi Syndrome cases in dogs, but certain toxins, medications and infections have been linked to its development in dogs and people."
  •  "When a person dies unexpectedly, it is not unusual for a medical examiner to perform an autopsy to try to determine the cause of death. When a pet dies, it is much less likely that qualified veterinary pathologists will have the opportunity to examine the body. By the time FDA receives reports of deaths in pets, the body often has already been cremated or buried, eliminating the chance for scientists to gather more information about potential causes for the pet’s illness. "
  • "Finally, FDA has limited access to market data about food items for pets. FDA regulations do not require product registration for foods, whether they are intended for people or animals. "

Many of these challenges and limitations can easily apply to the DCM investigation as well.  

 

    As early as 1998, an association was noted by veterinarians between acute kidney failure in dogs and recent ingestion of grapes or raisins. In 2001, these concerns were voiced in a JAVMA Letter to the Editor.  To this day, the toxic principle underlying this observation remains unknown. Not all dogs that ingest grapes experience signs of toxicosis, and a toxic dose has not been determined. 
Update: In March 2021, the reason for grape toxicity may have finally been uncovered. 
    Despite not understanding the pathophysiology of these observations, ingestion of any amount of grapes in any size dog is treated as a medical emergency by veterinarians and pet poison control centers, including recommendations for a medical professional to safely induce vomiting where indicated, collect baseline blood values and perform serial rechecks, and run IV fluids. Grapes and raisins are not necessary for the health of dogs, and with no way to predict which dogs will experience an adverse event, the safest approach is to treat every exposure as potentially deadly and provide medical intervention as such. 

    This example is not related to dogs or veterinary medicine, but instead helps to illustrate the scientific process within healthcare fields. 
    Like many fad products adopted throughout history, early tobacco use in Europe was associated with a variety of spurious health claims, from reducing anxiety to curing headaches, toothaches, and arthritis. It was the panacea. Popularized in the 19th century by soldiers in WWI, cigarettes became a preferred form of tobacco use. It wasn't until the beginning of the 20th century that scientists observed lung cancer was becoming more common. In 1950, four retrospective studies were published detailing lung cancer patient's smoking history. At this time, there was still debate over whether the perceived increase in lung cancer was real, or an artifact secondary to improved awareness and diagnosis. In one paper, the authors write that the evidence is based 'upon clinical experience and records,' and 'none of these small-scale inquiries can be accepted as conclusive, but they all point in the same direction.'  In another, authors write "There is strong circumstantial evidence that cigarette smoking was an etiologic [causative] factor in cancer of the respiratory tract."
    Despite the emerging evidence that had swayed the researcher's positions on the subject, it wasn't until seven years later that the US public health service issued a statement on lung cancer being caused by smoking. A January 1964 report from the Surgeon General contained the following excerpts: 
  • "Few medical questions have stirred such public interest or created more scientific debate than the tobacco - health controversy . The interrelationships of smoking and health undoubtedly are complex . The subject does not lend itself to easy answers . Nevertheless , it has been increasingly apparent that answers must be found ."
  • "It is not feasible to submit human beings to experiments that might produce cancers or other serious damage , or to expose them to possibly noxious agents over the prolonged periods under strictly controlled conditions that would be necessary for a valid test . Therefore , the main evidence of the effects of smoking and other uses of tobacco upon the health of human beings has been secured through clinical and pathological observations of conditions occurring in men , women and children in the course of their lives , and by the application of epidemiological and statistical methods by which a vast array of information has been assembled and analyzed."
  • "Among the epidemiological methods which have been used in attempts to determine whether smoking and other uses of tobacco affect the health of man , two types have been particularly useful and have furnished information of the greatest value for the work of this Committee . These are ( 1 ) retrospective studies which deal with data from the personal histories and medical and mortality records of human individuals in groups ; and ( 2 ) prospective studies , in which men and women are chosen randomly or from some special group , such as a profession, and are followed from the time of their entry into the study for an indefinite period , or until they die or are lost on account of other events ."
    Today, there is little controversy surrounding the claim that smoking cigarettes is a very prominent risk factor in the development of a wide variety of diseases and illness. While we have had decades to put together the breadth of knowledge informing this belief, research pertaining directly to the effects of tobacco on humans does still come primarily from retrospective and prospective studies, rather than double-blind clinical trials. 
    For similar ethical reasons cited above, it is unlikely that such gold standard research will ever be conducted on dogs in the context of diet-associated DCM. But several retrospective analyses have contributed to discussion surrounding this disease, and several prospective studies are underway. It's easy to imagine how many lives may have been prolonged had investigation into tobacco use not taken so long to grab hold of public attention and begin to sway beliefs surrounding it. Given the nature of the diets in question, particularly their lack of necessity or health benefits, it stands to reason that avoidance until this concern is either further confirmed or laid to rest may be in the best interest of potentially prolonging companion canine lives. 

Funding

    The FDA's investigation into non-hereditary DCM in dogs, and all other endeavors, are funded by USA taxpayers. Every fiscal year, the FDA is provided a budget appropriation. 
    The ongoing research at academic institutions are funded in a variety of ways, including donations from the public. For example, a retrospective analysis on diet and DCM published recently (Freid et al. 2020) was funded by the 'Barkley Fund,' a memorial fund set up by the owners of a dog that passed from cardiac disease. Some of these studies may be funded in part by companies in the pet food industry. To quote myself from another article on this topic: One would be hard pressed to find research experts in any field who have never received financial support from companies or corporations invested in that field. For better or worse, that's the nature of our current economy. That is why it's standard to disclose such connections and important to critically evaluate methodology and obtain peer-review for any scientific studies. Processes like peer-review are in place to mitigate risk of bias, and researchers are mandated to disclose any potential financial conflicts that could be construed. Critical examination is warranted, but we cannot presume that every study partially funded by a grant from a corporation was swayed in that corporation’s favor.  

Original FDA Request

    There is a common misconception that the FDA "only requested cases from dogs eating a grain-free diet," therefore causing a bias in the sample pool. The original FDA request did not specifically ask for cases from dogs eating grain-free diets. It reads: "The FDA encourages pet owners and veterinary professionals to report cases of DCM in dogs suspected of having a link to diet by using the electronic Safety Reporting Portal or calling their state’s FDA Consumer Complaint Coordinators."

    The reason that the FDA did not ask for reports of all cases of canine DCM is because there are instances where DCM can easily be explained by factors other than diet-- for example, an adult Doberman Pinscher with a family history of DCM. If the FDA had to sort through data on cases that veterinarians could easily determine are not likely to be dietary in origin, it would bog down the entire investigation. There are cases reported from dogs eating grain-inclusive diets. Grain-free diets just vastly outweigh them. This doesn't appear to be a coincidence or isolated sample bias-- studies have also shown an association between non-traditional diets (like grain-free) and DCM when compared directly to dogs eating more traditional diets. 

    It's easy to wonder if some aspect of this boils down to a trend between what types of food people purchase and how likely they are to get an illness diagnosed by a veterinarian. However, to borrow a phrase from those pushing back on this issue, consumer purchasing behaviors are complex and multi-faceted. There are many assumptions that have to be true in order for this logic to follow. Even if we accept the assumption that the amount people spend on pet food correlates with the amount they're willing or able to spend at a veterinary clinic, there are both expensive and inexpensive grain-free diets, and both expensive and inexpensive grain-inclusive diets. Even still, it would be difficult to explain away such huge disparity between market share and the overrepresentation of some of the named manufacturers with the claim that those specific people feeding that specific food are the only people that take their pets to the vet or pursue advanced imaging and diagnostics. 
    There are also other scenarios to consider, even if we assume that grain-free diets are 'expensive' and grain-inclusive diets are 'cheap.' For example, what if someone spends less on dog food so that they can afford emergency care or advanced diagnostics for their pet? What if someone spends so much on a dog food that they believe is best that they can't afford expensive veterinary bills? Brands like Purina Pro Plan are popular among show and sport breeders and canine sport enthusiasts. Many of these dog receive health clearances, including an echocardiogram. 
    There is likely no doubt that certain socioeconomic circumstances preclude a diagnosis of DCM. But we shouldn't assume that consumer buying behaviors have such a large sway over willingness to spend on veterinary bills that it explains away the disparity observed in case reports. Additionally, studies comparing dogs eating non-traditional and traditional diets have continued to identify a link between non-traditional diets and heart abnormalities. These studies don't eliminate all extraneous variables, but they do remove the assumption that dogs eating traditional diets aren't being examined for heart health.  

Prevalence

    The full scope of this issue is unknown for many reasons. Short of collecting a large random sample of dogs to be evaluated by cardiologists, we can't possibly hope to estimate how many animals are affected. DCM can exist as an occult disease, meaning the dog in question is asymptomatic. Even in dogs that have symptoms, those symptoms may be vague, non-specific, or even so subtle that they go unnoticed: decreased energy, lethargy, lowered exercise tolerance, an occasional cough. DCM can occur with arrhythmia, or abnormal heart rhythms, which are a risk factor for sudden death. Without an autopsy, which owners may not pursue for a number of reasons, that cause of death may never be determined. While not all dog owners are aware of an autopsy as an option, others lack the funds to pursue one, or elect not to in order to keep the remains of their pet. As discussed in the 'Annual Exams' section below, DCM is not something that would be picked up through routine canine healthcare. Even for owners with suspicion that their dog may be ill, there are barriers to the accessibility of veterinary cardiology services. These barriers may be geographic (no local practices), financial (specialty care is expensive), or simply the inability to make an appointment due to a high caseload seen by the relatively few cardiologists in the USA. 
    All of this means that the cases reported to the FDA (now >1100) are only the tip of the iceberg-- the cases that were both diagnosed and reported. Under the surface, you have an expanding base: cases diagnosed but not recorded, dogs with clinical signs that haven't been diagnosed, dogs without clinical signs that haven't been diagnosed, and dogs that died suddenly without an autopsy performed and will never be diagnosed. 
    Some mistakenly claim that unless 100% of dogs eating certain diets develop disease, diet is not the underlying cause of the disease process. However, many known risk factors for diseases exist that do not impact 100% of the exposed population, due to individual differences in genetics, environment, and epigenetics. For example, not 100% of people with chronic sun exposure will develop melanoma. Not 100% of people that smoke will develop lung disease. Not 100% of people with high cholesterol will develop heart disease. Biological systems are complex, and it may be centuries before we fully understand all the nuance underlying them. However, that does not preclude recognizing avoidable factors that cause a substantial increase in lifetime risk of certain diseases. 
    As of right now, there is no large-scale data available tracking cases of DCM seen by the ~300 cardiologists in the USA. Such data may make it easier to determine to what extent atypical breeds are presenting with this disease. However, collecting such data at the necessary scale would require the time and cooperation of dozens, if not over 100 institutions that may have no easy way of procuring it. Until such data can be collected, the reported experiences of clinicians seeing these cases should be sufficient to at least raise a flag of vigilance and concern.  
    Many individuals less cautious of this issue cite their annual exams with their vet as evidence of their pet's good health, despite feeding a grain-free or otherwise non-traditional diet. While annual exams are important for tracking your pet's general health over time, DCM is a disease that is not frequently revealed through standard routine diagnostics. DCM rarely causes a heart murmur that can be heard through your vet's auscultation by stethoscope. DCM may cause arrhythmias, but most dogs do not routinely get an EKG during their annual exam. Dogs with DCM may show no symptoms (occult disease). While a specific blood test, ProBNP, may suggest underlying heart disease, it is not routinely performed, and it isn't perfect. A standard blood panel would not show DCM. X-rays may show an enlarged heart, but are rarely recommended for otherwise healthy pets. An echocardiogram with a cardiologist is the only way to definitively diagnose a dog with DCM. 
    One reason some pet owners are reluctant to switch away from grain-free diets (or other non-traditional diets) is often cited as the very reason they started purchasing them in the first place-- the perception that they're healthier, safer, or hypoallergenic. However, there is no evidence that shows grain-free diets are associated with unique health benefits when compared to the more traditional, grain-inclusive diet formulations. Grain allergies are also incredibly rare, even as a subset of adverse food reaction which themselves are estimated to affect no more than ~10% of dogs with atopic dermatitis (itchy skin). These reactions are most commonly to chicken or beef. While grains are often reported on food allergy panels, these tests are notoriously inaccurate. 
    Even if a pet had a severe, broad allergies to grains (which is virtually unheard of), a commercial grain-free diet would still pose problems as cross-contamination of commercial pet foods is well documented to be an issue between formulas, with many diets containing trace amounts of undeclared proteins. 

Read more on this from the Clinical Nutrition Service at Cummings School of Veterinary Medicine at Tufts. 

Taurine / Grains

    A lot of people ask if they can just supplement taurine or add grains like boiled rice into their dog's food. There are several problems with this approach, the first and foremost being that we don't know that either of those things (insufficient taurine, or the actual absence of grains) are the underlying cause of these observations. Not all of the dogs reported to the FDA have tested low for taurine, and adding ingredients to a commercial diet runs the risk of introducing nutrient deficiencies by unbalancing the formulation. Rather than trying to fix a potentially broken diet, the safest thing to do is switch away from it until we know more. If some underlying common thread between these diets turns out to be, for example, something impairing taurine metabolism, no amount of added taurine would help unless the diet was also changed. 
    A common follow-up to that is confusion surrounding why many dogs are receiving taurine supplementation alongside a diet change after being diagnosed. In the simplest terms, this is being done just in case it helps expedite recovery. The recovery itself is still strongly thought to be predicated on the diet change itself.  

Grain-Inclusive Foods

    Many of the researchers investigating this issue believe the underlying cause to ultimately be one of poor formulation, not necessarily the inclusion of exclusion of any particular ingredients alone. That said, out of an abundance of caution, it may be best to avoid diets from any manufacturers with a significant number of case reports/complaints, even if the specific diets of interest are grain-inclusive, until more information is available. Grain-free diets or diets high in pulse legumes such as peas, chickpeas, or lentils, may also be worth avoiding, particularly in the absence of medical indication to feed such as diet. The next section contains some suggestions for considerations to have when evaluating pet foods. UC Davis has published guidelines as well: "While avoiding all suspect ingredients may be the most direct way to select a new diet, we suggest that a small amount of legume content in a well-formulated grain-inclusive diet may be OK. Our guidelines allow for no more than two legume ingredients in a grain-inclusive diet when found low on the ingredient list (below all meat and grain content). Importantly, these diets should still be tested by AAFCO feeding trial."

Choosing a Pet Food

    The World Small Animal Veterinary Association has put together a list of recommended questions to ask a pet food manufacturer when deciding on what to buy. These questions aren't comprehensive, and WSAVA doesn't advise how you should expect a company to answer, but they are a good place to start. Some people have criticized certain standards as being prohibitive to smaller companies. However, if a company cannot afford bare minimum standards for formulation and production quality, they should not be manufacturing dog food. Using the WSAVA recommendations and the advice of several veterinary nutritionists, here is what you should look for:

1. Companies should employ at least one, dedicated full-time nutritionist, and ideally, they should have several. This would be someone with a PhD in animal nutrition or a veterinarian boarded in nutrition as a specialty (DACVN). Some companies will state they 'work closely with nutritionists' or 'consult with a nutritionist.' While these are good practices, a consultant cannot provide the same level of dedicated and detailed oversight to formulation and product management as a full-time employee, or team of employees, can. 

2. The diets should be formulated by someone qualified to do so- such as a veterinary nutritionist. Experience in the pet food industry, or owning dogs, regardless of how many years, does not alone qualify someone to formulate diets. Much like in the first case, a team of qualified expert professionals is even better than just one or two. In the best case scenario, there will be not only nutritionists, but food scientists and toxicologists involved as well. 

3. Diets should undergo feeding trials that, at a minimum meet, and ideally exceed, AAFCO standards/protocols. In addition to feeding trials, diets should be formulated to meet nutrients profiles and undergo analysis of the finished product to confirm nutrient levels. Testing diets only for digestibility or palatability, or meeting AAFCO standards by formulation or analysis alone, is less ideal. 

4. Foods should be produced in facilities owned and operated by the manufacturer so that every aspect of production can be closely monitored. Ideally, foods sold in the USA should be manufactured in the USA. These facilities must be equipped with machinery, laboratories, and staff that can provide extensive, on-site quality assurance. Manufacturers that contract with a third party facility to produce their foods lose some degree of control over quality and also risk cross contamination if there are issues that arise with other diets produced at those facilities. 

5. Manufacturers should have transparent and extensive quality control protocols. This should include selection criteria for partners, analysis and sample tracking of externally sourced ingredients such as vitamin mixes, daily safety checks of product batches and facilities, physical inspection, and key nutrient testing before final packing. Some companies will save samples from each batch/lot in order to re-evaluate or investigate that diet should issues arise later. The presence of a recall history does not preclude a manufacturer having good quality control. However, the frequency with which recalls occur, the nature of the recall, and the manner in which the company proactively responds should be considered. 

6. Companies should be able to provide a complete nutrient analysis for any food they produce on an energy basis (grams per kcal) and additional information such as digestibility. 
7. They should have information on the caloric value for any formula readily available in kcal per gram diet and per cup. 

8. Companies should be investing in and conducting nutrition research that is relevant to the diets they are putting out onto the market, particularly when making health claims or introducing a novel formula that strays from traditional or well-researched norms. This research should be peer-reviewed and published. It is a red flag for a company to claim research as 'proprietary' and unavailable for review. Companies that do not engage in any research endeavors, or worse, actively oppose nutrition research, may be best avoided. 

Additional Resources

Published Research


DCM Resources / Reading

    Sub-group for Veterinary Professionals


General Pet Nutrition Resources / Reading

WSAVA: FAQ, Guide to Nutrition on the Internet (Dogs) (Cats)

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