Veterinarians Say Many Commercial Dog Foods Are Slowly Killing Our Pets

Is your dog overdosing on the copper supplements in their food veterinarians speak out about AAFCO regulations on copper chelates and copper sulfate

Is Your Dog Overdosing on the Copper Supplementation that is Mandated by AAFCO?

Veterinarians say dogs are being slowly poisoned by many commercial dog food products.  This poisoning is a result of a fault in the nutritional regulations governing dog food, and has been happening for the last 25 years.  They have documented this poisoning through scientific study, and their rising voice is calling upon FDA and AAFCO to fix it now.

Following FDA and AAFCO regulations, many manufacturers include unsafe amounts of highly-bioavailable manmade copper supplements in their complete and balanced dog food formulations.  These troublesome copper supplements come as either copper sulfate or copper chelates (also called copper proteinate, copper amino acid chelate, chelated copper, copper lysine, copper glycinate, copper bisglycinate).

Objective data validates that “allowances for dietary copper mandated by regulatory agencies [NRC and AAFCO] exceed physiologic tolerance for many healthy dogs,” says veterinarian Dr. Sharon Center, Emeritus James Law Professor of Internal Medicine at Cornell University’s College of Veterinary Medicine.  Dr. Center says that the problem stems from a 1997 change by AAFCO to copper supplements.

Dr. Center is nationally renowned for her expertise in feline and canine liver diseases.   She says the addition of copper supplements in the form of copper chelates or copper sulfate in commercial dog food can cause a serious, potentially lethal, illness called dietary-induced, copper-associated hepatopathy (CAH).   

The addition of copper supplements in the form of copper chelates or copper sulfate in commercial dog food can cause a serious potentially lethal illness called dietary-induced copper-associated hepatopathy (CAH) Sharon Center DVM

Copper chelates and copper sulfate replaced copper oxide on AAFCO’s approved list in 1997, and in 2007 the upper limit of copper in complete and balanced formulations was eliminated by AAFCO.  Copper chelate is a form of copper bound to an amino acid to make it more bioavailable.   

Some studies indicate that the bioavailability of copper chelates and copper sulfate can approach 90% while copper oxide and the natural copper found in food generally has 30% - 40% bioavailability.  These studies also show that mammals are very adept with regulating natural copper from food, absorbing only what is needed and eliminating the rest in the stool.

“Because dogs are fed the same daily ration, dietary formulations can have a cumulative impact.  There is a notable relationship between dietary formulations and a progressive increase in liver copper concentration over time since the popularization of commercial dog food in the late 1940s [with the] highest values realized since the most recent change in copper supplements,” warns Dr. Center in a presentation to FDA.

Moreover, without an upper limit on copper, manufacturers can include very high levels of copper chelates or copper sulfate in their formulations. A review of data from the Missouri Department of Agriculture on the copper content of popular cat foods conducted by the advocacy efforts of Truth About Pet Food found brands that exceeded the regulatory minimum by as much as 780%. 

Veterinary Research and Published Studies Provide Evidence of Poisoning by Copper Chelates and Copper Sulfate

According to JAVMA published research conducted by a working group of six veterinarians, the copper concentration in the livers of dogs has increased from < 10 µg/g in 1929 (before the availability of commercial dog foods) to 200 µg/g in 1982, to 453 µ/g in 1995.  Results of another 2015-2020 study of 116 dogs with cirrhosis, showed that 65% had copper levels > 1,001 µg/g suggesting a causal relationship, according to this same scientific paper. 

rates of copper associated hepatopathy are increasing in dogs due to AAFCO requirements for chelated copper and copper sulfate in dog food

Another 2018 retrospective study of 546 archived liver specimens from dogs without a pre-disposition for CAH looked at the mean copper content in dogs' livers across two time periods: 1982-1988 (before the AAFCO change in copper formulation) and 2009 - 2015 (after the AAFCO change).  They found a significant increase in mean copper concentration in the later group and concluded "the close temporal association of changes in [Cu]H with changes in AAFCO copper supplementation recommendations are concerning."

This finding echoed a 2013 study of Labrador Retrievers with and without chronic hepatitis in the periods of 1980- 1997 and 1998 - 2010 and "found that hepatic copper concentrations were significantly higher after the recommendation to alter sources of copper in commercial dog foods than they had been before that change in formulation."

And again, another small study comparing feral dogs fed human scraps and foraged foods to purpose-bred dogs fed commercial dog food came to this same conclusion.  The feral dogs had hepatic copper concentrations ranging from 69 – 370 µg/g (median: 152 µg/g) which was significantly lower than the range in commercially fed dogs of 199 – 997 µg/g (median: 472 µg/g).

How Dangerous is Copper Over-Accumulation to Dogs?

Over-accumulation of copper in the liver provokes oxidative injury. “The net reaction is the generation of the injurious hydroxyl radical that can independently cause cell death or worsen co-existent diseases. Copper associated liver injury in dogs is insidious in onset. With chronicity, it can be lethal leading to cirrhosis or panlobularnecrosis,” said Dr. Center in her presentation to the FDA. 

Cheat Sheet to Identify Chelated Minerals Like Copper Proteinate And Copper Sulfate Used In Dog FoodAn acquired Fanconi syndrome (abnormal kidney function) is occasionally encountered in some dogs, typically those with advanced disease, according to the February 2021 article published in the Journal of the American Veterinary Medical Association.

Early recognition of this disorder is difficult as dogs do not demonstrate signs of illness. According to Dr. Center, "any dog frolicking on the beach could have early copper associated hepatopathy as could your dog right now at home." 

Typical diagnosis starts with increase serum ALT activity (one of the liver enzymes) that vacillates.  With more advanced disease, dogs develop obvious laboratory, physical and imaging findings indicative of severe liver injury. These dogs are more difficult to treat and have a more dismal prognosis, according to Dr. Center. 

Definitive diagnosis requires liver biopsy by laparoscopy or open surgical methods because needle biopsies are less accurate and aspirates are ineffective. Cost associated with this disorder involve the diagnostic and treatment expense -- each ranging as high as $5,000.  CAH also impacts pets with surgical and anesthetic risks and biopsy-associated discomfort as well as owner emotional distress, says Dr. Center.

AAFCO Regulations Have Caused Dogs to Overdose on Manmade Copper Supplements

So why was the change made in 1997 to a more bioavailable form of copper supplementation?  There is no good answer, according to Dr. Center.   She says that “this change was instituted despite no evidence of copper insufficiency in any pet dog that we know of fed commercial diets.”

Highly Bioavailable Copper Amino Acid Chelate and Copper Sulfate Are Causing Illness In Dogs Natural Copper In Base Diets Is Adequate Nutrition And Safe

Dr. Center reports that the AAFCO regulation replacing copper oxide with highly available copper chelates resulted from only a published abstract of a small scientific study that concluded low bioavailability of copper oxide.  The data from that study was never published as a peer reviewed manuscript.  Moreover, the baseline diet was not distinguished in the abstract.  Underlying diet is important to evaluate, as the way food is processed, and the protein and carbohydrate levels as well as other minerals (e.g. iron, zinc, calcium) in the food can affect copper absorption.

 “Current copper intake clearly exceeds the limit of tolerance for a substantial number of dogs,” says six authoring veterinarians in the JAVMA article.  They are calling upon AAFCO to define an upper tolerability limit.  Interestingly the earlier, repealed limit was based on a study of swine which are particularly resistant to CAH.

Because copper oxide lacks bioavailability, it is probable that base diets  deliver biologically adequate copper intake,” says Dr. Center [emphasis added].  “Change can and should be made without studies to determine minimum copper intake. The FDA and AAFCO need to empower pet food companies to decline copper additives if governing actions are delayed,” she stressed in her FDA presentation.

Whole Food Diets Can Protect Your Dog From Copper Overdose

So what steps can pet parents take today to protect their dogs?  They can look for high-quality commercially available foods that are complete and balanced using 100% whole foods.  These products source copper strictly from natural food sources that the body can easily recognize and regulate.  Goodness Gracious makes four human grade gently cooked whole-food diets for adult maintenance, with 100% natural copper levels that are as low as 1.94 mg/1000 kcal.

Goodness Gracious human grade whole food diets for dogs complete and balanced with natural copper vitamins minerals

Pet parents also can look for foods where the copper levels are close to the current AAFCO minimum and well below the old maximum.  For canine adult maintenance, the AAFCO minimum requirement for copper is 1.83 mg / 1000 kcal and the old maximum was 71 mg/1000 kcal.  Parents may have to contact the manufacturer to obtain this information as copper levels are not usually disclosed on labels.

Dr. Center also reports that copper-restricted diets for dogs with CAH or copper storage disease appear to be fine for healthy dogs -- meaning that healthy dogs on these diets have not developed copper insufficiency problems in her experience.  Be careful with these diets though, as they are often made with poor, livestock feed-grade quality ingredients such as "byproduct meals" and hefty amounts of feed-grade corn and rice.  (Byproduct meals are rendered substances that can come from unslaughtered 4D animals.)  There are better ways to reduce the copper with your favorite brand than opting for a product with these kinds of inedible ingredients.

One way is to cut the portion of your favorite brand by 25% - 50% and substitute the calories with a whole food diet - be it commercially available or homemade. We provide recipes for homemade compete and balanced meals here and a formula for DIY'ers here.

Pet parents are also advised to speak with their veterinarians about nutraceuticals like SAMe, milk thistle and vitamin E that can support liver health and detoxification from copper accumulation, and tests to evaluate their dog’s health. 

Dr. Center told FDA that she and the CAH working group of veterinarians are "available to assist with the mitigation of this avoidable and tragic nutritionally provoked canine illness."


Copper Associated Hepatopathy in Dogs Caused By AAFCO Dietary Regulations A Presentation By Sharon Center DVM To FDA
Watch Dr. Center's Presentation to FDA on YouTube.  Tune in at 1:12 and listen to Dr. Center's eight (8) minute presentation on copper associated hepatopathy to FDA.


AAFCO (Association of American Feed Control Officials). An organization with an “understanding” with FDA to develop the regulations for animal feed (inclusive of pet food). This organization has no enforcement authority.  Enforcement of laws is done at the federal level by the FDA and at the state level by a state’s department of agriculture (or equivalent).

FDA:  If your dog has been diagnosed with copper hepatopathy, please ask your veterinarian to complete the FDA questionnaire at  You are also advised to report your pet’s diagnosis to pet food advocate Susan Thixton at

Additional References:

Is it time to reconsider current guidelines for copper content in commercial dog foods?

EFSA Scientific Opinion on chelated minerals