Cornell study renews scrutiny of copper in commercial dog food
Bottom line
New Cornell-led research is sharpening concern that excess copper in commercial dog foods may be contributing to silent liver injury in older dogs, reviving a debate that regulators and industry have so far resisted settling. A 2025 JAVMA study led by Dr. Sharon Center found lower risk of hepatic copper accumulation in dogs fed copper-restricted diets than in dogs fed copper-replete diets, based on liver samples from 104 geriatric dogs collected between April 2023 and April 2024. The work builds on Center’s earlier 2021 JAVMA viewpoint urging a rethink of current copper guidelines in commercial dog foods, and comes after AAFCO declined in May 2024 to adopt a voluntary “controlled copper” labeling claim for dog food. (pubmed.ncbi.nlm.nih.gov)
Why it matters: For veterinary professionals, the story is less about a single paper than a growing body of evidence that copper-associated hepatopathy may be underrecognized, especially in older dogs without obvious early clinical signs. Current AAFCO nutrient profiles set a minimum copper level for adult maintenance diets, but no upper limit, and veterinary nutrition sources note many commercial diets deliver copper well above the minimum. That leaves clinicians managing a problem that can be difficult to detect early, while pet parents often have limited access to copper data on labels. (aafco.org)
What to watch: Watch for whether the new JAVMA data prompts renewed FDA or AAFCO review, especially around labeling transparency, voluntary claims, or future discussion of a maximum or more tightly defined copper standard. (fda.gov)
A new Cornell-led study is adding weight to a long-running veterinary debate over copper in commercial dog food, with implications for screening, diet history-taking, and client counseling in general practice. The study, published in JAVMA in late 2025 and led by Dr. Sharon Center, reported a lower risk of liver copper accumulation in dogs fed copper-restricted diets compared with dogs fed copper-replete diets. The findings arrive after several years of warnings from Center and other hepatology experts that some commercial diets may be supplying more copper than some dogs can safely handle over time. (pubmed.ncbi.nlm.nih.gov)
The current controversy traces back at least to a 2021 JAVMA viewpoint by Center and colleagues that asked whether existing copper guidelines for commercial dog foods should be reconsidered. That paper argued that hepatic copper concentrations in dogs had risen over time and raised concern that regulatory shifts, including more bioavailable copper sources and the absence of an upper limit in U.S. guidance, may have contributed. In response, AAFCO convened an expert panel, but in March 2023 said the evidence was still insufficient to establish a science-based safe upper limit for copper in normal dog foods. (pubmed.ncbi.nlm.nih.gov)
The latest JAVMA study gives that debate fresh data. According to the PubMed record, investigators collected liver samples from 104 dogs euthanized for geriatric health concerns between April 7, 2023, and April 22, 2024, and paired those findings with medical records, dietary histories, and copper analyses of diets and regional water. The study’s central conclusion, reflected in its title, was that dogs eating copper-restricted diets had lower risk for liver copper accumulation than dogs eating copper-replete diets. Cornell amplified those findings in a January 8, 2026 news item tied to The Canine Review coverage. (pubmed.ncbi.nlm.nih.gov)
Regulatory action, though, has lagged behind the clinical concern. FDA’s Center for Veterinary Medicine publicly acknowledged the issue in a February 8, 2024 Grand Rounds presentation focused on the scientific and regulatory challenges of reconciling copper-associated hepatopathy concerns with pet food rules. AAFCO then considered a voluntary “controlled copper” claim, and a workgroup proposed language that would have limited qualifying dog foods to no more than 15 mg copper/kg dry matter and no more than 3.75 mg copper/1000 kcal, with a labeled maximum copper guarantee. But on May 30, 2024, the AAFCO Pet Food Committee voted against adopting that voluntary claim, saying consensus was lacking. (fda.gov)
Industry and expert reaction remains divided, though not necessarily dismissive. AAFCO’s position has been that regulators should not set a maximum without stronger cause-and-effect evidence showing what level would actually protect dogs from liver disease. At the same time, veterinary nutrition commentary has acknowledged that copper-associated hepatopathy is a real clinical problem, and that many commercial diets may contain copper well above minimum requirements. A 2024 Today’s Veterinary Practice review noted a median copper concentration of 4.4 mg/1000 kcal among 45 over-the-counter diets, about 2.4 times the AAFCO adult maintenance minimum, and suggested manufacturers more closely monitor ingredients, premixes, and final product copper levels. dvm360 coverage has similarly described rising concern among veterinary nutrition specialists about copper storage-related hepatopathies. (aafco.org)
Why it matters: For veterinarians, the practical takeaway is that copper-associated hepatopathy may be both more common and more clinically silent than many pet parents realize. Older dogs, predisposed breeds, and dogs with unexplained liver enzyme elevations may warrant a more detailed dietary history, including specific questions about over-the-counter foods, treats, organ meat content, supplements, and long-term feeding patterns. The lack of clear on-label copper disclosure for most products also means clinicians may have to work harder to obtain nutrient data from manufacturers or pivot to therapeutic diets when copper restriction is indicated. (todaysveterinarypractice.com)
The issue also sits at the intersection of internal medicine and nutrition practice. Copper is essential, so the question is not whether it belongs in canine diets, but whether some formulations, ingredient combinations, or supplementation practices are pushing intake too high for susceptible dogs over years of exposure. That makes this a population-level nutrition question, not just a niche hepatology problem. If Center’s estimate that millions of dogs may be at risk gains wider acceptance, pressure could increase for more transparent labeling, stronger post-market surveillance, and updated nutrient-profile discussions. That last point is partly an inference from the regulatory history and new research trajectory, rather than a formally announced policy move. (pubmed.ncbi.nlm.nih.gov)
What to watch: The next key markers are whether FDA or AAFCO revisits copper guidance in light of the new JAVMA paper, whether manufacturers voluntarily disclose more copper data, and whether additional peer-reviewed studies help define which dogs are most vulnerable, at what intake thresholds, and over what time horizon. Until then, this remains an evolving clinical-research story with immediate relevance for nutrition counseling and chronic liver disease workups. (pubmed.ncbi.nlm.nih.gov)