This article was published in the January 2024 issue of Pet Food Processing. Read it and other articles from this issue in our January digital edition.

In the ever-evolving landscape of pet nutrition, a new debate is occurring around copper levels in pet diets and their potential link to hepatopathy, a type of liver disease, in dogs. This discussion taking place within the veterinary community today echoes earlier, highly publicized concerns about grain-free diets and their potential link to a heart condition called dilated cardiomyopathy (DCM). Given the significance of such claims and the pet industry’s commitment to the health and wellbeing of animals, it is important to be aware of these concerns. At the same time, we must scrutinize all such developments through the lens of controlled, prospective research that can observe and identify trends over time.

“The current debate over copper in pet food should serve as a rallying cry for the industry to advocate for sound scientific prospective research,” wrote Stephanie Clark, Sydney McCauley and Bradley Quest of BSM Partners.

Drawing parallels to the problems created by DCM, a researcher at The Veterinary College of Medicine at Cornell University is currently delving into copper levels by requesting nutritional information from pet food manufacturers and advocating for maximum copper levels. Similar to the initial rumblings and origins of the DCM controversy, the push to scrutinize copper mirrors the methodology that sparked the controversy around DCM, namely a reliance on anecdotal observations and retrospective case studies with significant limitations that cannot nor should not be used to draw sweeping conclusions. Upon further inspection, we also see other similarities, from claims about an increase in the incidence rate of copper-related disease, the use of case studies that include predisposed or already sick animals, and opinion pieces being taken as objective data. The importance of learning from past experiences and demanding more robust research methodologies cannot be overstated.


Claims of incidences on the rise

The absence of concrete data supporting the purported increase in DCM cases in 2019 mirrors the uncertainty surrounding copper-associated hepatopathies. In the case of DCM, there was no large-scale data published to support these beliefs. However, a commentary published by the Journal of the American Veterinary Association (JAVMA), which anchored concerns that helped fuel the Food and Drug Administration’s (FDA) public comments on the issue, alleged that “over the past few years, an increasing number of DCM cases involving dogs appear to have been related to diet.”

Subsequent analysis of information shared by the FDA under the Freedom of Information Act (FOIA) undercuts any notion of an increase in DCM. Furthermore, a published, peer-reviewed analysis of data collected from veterinary cardiology clinics across the country found the incidence of DCM remained relatively flat over the last 20 years.

Similarly, in 2022, The College of Veterinary Medicine at Cornell published that there was, “Certainly a rise in copper-related hepatopathies.” The authors of a 2021 viewpoint article in JAVMA, which was also reposted in an AVMA News article, claimed, “Over the past 15 to 20 years, we have seen what we believe to be an increased incidence of copper-associated hepatopathy in dogs.”

Natural sources of copper

Dietary copper makes its way into dog food formulas through the inclusion of ingredients like beef liver, flaxseed, buckwheat, barley, sweet potatoes and others. 


Despite this comment, the actual incidence rate of copper-associated hepatopathy in dogs is still unknown. Acknowledging the rise in awareness and testing, it is crucial to differentiate between heightened awareness and genuine increases in incidence, as demonstrated in the DCM scenario.


Removing outliers

Concerns about a rise in disease around copper and grain-free diets are rooted in the notion that hepatopathy and DCM are suddenly being observed in dogs that are not already genetically predisposed to developing either disease. There will also be animals that are already sick or have existing illnesses that can be precursors (co-morbidities) to the disease in question. So, when assessing records of dogs diagnosed with hepatopathy or DCM, scientists must screen out both of those groups. However, this is not what happened with DCM. The link between copper restriction and hepatic disorders in certain breeds should not be extrapolated to healthy dogs, but this is exactly what some researchers appear to be doing.

Veterinary researchers spent hundreds of hours analyzing a FOIA request for all the FDA information, including medical records, obtained of all dogs referenced in the FDA’s June 27, 2019, public release on the number of cases of diet-associated DCM that they received from the public.

The results of that analysis are as follows:

  • The FOIA release mentions only 361 dogs reported to the FDA when it was claimed that 560 dogs had been reported to the FDA from Jan. 1, 2014, through April 30, 2019.
  • 143 of the 361 dogs identified were confirmed as being predisposed breeds to DCM.
  • 160 of the 361 dogs identified had some form of a medical record identified in the FOIA release, the others did not.
  • Of the 361 reported dogs, 62 had a co-morbidity that could impact cardiac function, and 34 dogs had a co-morbidity that could directly contribute to a DCM diagnosis.


Confusion for pet owners 

When pet owners are faced with situations where the science is unclear but scary news headlines are abundant, they don’t know who to trust and don’t have enough information to make an informed decision. As we saw in the case of DCM, they turn to veterinarians who similarly are not nutritionists and don’t have enough time to stay abreast of the latest developments.

When pet owners are faced with situations where the science is unclear but scary news headlines are abundant, they don’t know who to trust and don’t have enough information to make an informed decision,” wrote Stephanie Clark, Sydney McCauley and Bradley Quest of BSM Partners.

As recently as 2016, there were concerns in the veterinary community that there were insufficient levels of copper in pet food, which then led to an increase in requirements for copper under the Association of American Feed Control Officials (AAFCO). Today, some veterinarians are claiming that there is too much copper. How is a brand or a manufacturer to know what is correct? 

The only way to do so is to help support prospective research, with control groups and a large enough number of dogs. This is the only true method to validate and improve the guidance provided by nutritional guidelines that impact the nutrition of 80 million dogs in the United States alone. Clinical trials with anecdotal treatments, though essential for sparking research conversations, cannot ever provide definitive conclusions.


Focus on brands, not nutrition

A critical concern arises with brand-shaming, exemplified by the FDA’s release of 16 brand names associated with reported cases of DCM. Executives must recognize the risk of regulators or veterinarians prematurely drawing causation without thorough investigation. This scenario was evidenced by the discrepancy between reported DCM cases and a lack of meaningful documentation about dogs’ diet history.

The potential establishment of arbitrary maximums for copper levels raises similar issues, implying the safety of brands based on unproven thresholds. We see the Cornell-based researcher’s attempts to solicit information from brands as a similar approach used by some of the researchers who were behind asserting that grain-free pet food was causing DCM.


Opinion-based articles amplify confusion

A recommendation is being circulated through AAFCO to include “low copper” claims, adding another layer to the complex landscape. The proposal of the “low copper” claim reported to the AAFCO Expert Panel was based on the JAVMA viewpoint article. This exact situation draws similarities to the 2018 commentary, published in JAVMA, drawing a correlation and causation of BEG (boutique brands, exotic protein, and grain-free) diets to canine DCM.

Copper levels in dog food have emerged as a possible culprit for liver disease, but more research is needed before jumping to conclusions

According to experts at BSM Partners, more research is needed to examine a potential link between copper levels and liver disease in dogs before sounding the alarm to consumers.


This opinion-based article was misinterpreted as objective scientific data by pet owners and the FDA. There have been at least two retraction letters for this article with over 200 signatures from veterinarians, animal scientists and other pet industry personnel in support of removing the article that is causing so much confusion.

These opinion pieces can lead to massive market issues. For example, if there is an arbitrary upper limit, almost every product on the market is going to be suspect and would need to be tested and potentially reformulated. Therefore, it is imperative to navigate the fine line between responding to consumer concerns and avoiding premature, non-scientifically supported claims that may fuel market instability.

The current debate over copper in pet food should serve as a rallying cry for the industry to advocate for sound scientific prospective research. Nutritional guidelines pivotal to the health of pets should only evolve based on thorough scrutiny and unbiased expert reviews. As leaders in the industry, fostering an environment where decisions are informed by comprehensive, rigorous research and ensure the wellbeing of pets remains the priority.

Stephanie Clark, Ph.D., CVT, PAS, CFS, Dpl. ACAS, VTS (Nutrition) is a board-certified companion animal nutritionist and assistant director of Special Services at BSM Partners. Sydney McCauley, Ph.D., PAS, Dpl. ACAS is a board-certified companion animal nutritionist and manager of Product Innovation at BSM Partners. Bradley Quest, DVM, is the principal of Veterinary Services at BSM Partners. 

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