Drilling For Dietary Copper

Last month, in “Excessive Copper in Dog Food,” we told you how high copper levels in dog food can cause a serious, potentially lethal, illness called dietary-induced, copper-associated hepatopathy (CAH, also known as copper storage disease). The incidence of CAH is increasing at a rate that’s causing alarm among veterinarians and dog owners, with one study showing 30% of canine liver biopsies revealing evidence of CAH. 

In that article, we stated that currently, the “recommendation” for the amount of copper in a dog food is 7.3 mg/kg (milligrams of copper per kilogram of food). That’s not quite right – but only because the American organization that sets the standards for what constitutes a complete and balanced diet doesn’t publish recommended levels of any nutrient, just minimums and a few maximums. We should have said that the current legal minimum for copper in a non-prescription dog food is 7.3 mg/kg – and owners of dogs who are at risk of developing CAH would be wise to feed only foods with copper levels as close to the minimum as possible.

The European Pet Food Industry Federation (FEDIAF) uses a similar number (a small range, actually) for a minimum copper value in dog diets (7.2 to 8.3 mg/kg) – but it also imposes a maximum value for copper: 28.0 mg/kg. In contrast, the U.S. does not currently impose a maximum allowed value for copper, and it’s easy to find dry dog foods in the U.S. that contain copper levels that far exceed that amount. 

Labrador Retrievers are considered at high risk of CAH, as are Bedlington Terriers, Dalmatians, Doberman Pinschers, and West Highland White Terriers. But CAH has been diagnosed with increasing frequency during the past decade in various pure and mixed-breed dogs that are not typically considered predisposed to pathologic copper accumulation. So this issue should be of concern to everyone who feeds their dog a commercial diet.

WHAT CAN YOU DO ABOUT COPPER IN DOG FOOD? 

To protect your dog, the first step is to learn how much copper is in your dog’s food; the second is to make sure you feed products with lower copper levels. Taking that first step, unfortunately, often means contacting the maker of your dog’s food and asking about its copper content. And to appreciate the answers to these questions, you first need to understand the terms that may be used in those answers. 

Nutritional values may be reported in one of three ways. To compare products, you may have to convert the values reported to you into a different form (or ask the pet food company if they can give you the values in the specific form you need). The three ways that nutrient values may be expressed are:

• As fed. The nutrient levels that are printed on dog food labels are expressed “as fed” – the values given are for the food in its packaged form. For example, Royal Canin’s dry prescription “Hepatic” diet lists its copper content as 7 mg/kg (max) as fed. This means there are a maximum of 7 milligrams of copper per kilogram of the food. 

Note: Some food companies may use “parts per million (PPM)” instead of mg/kg. Mathematically, parts per million is equivalent to milligrams per kilogram; 4 ppm is the same thing as 4 mg/kg.

• Dry matter (DM). These values represent the amount of a nutrient present in the food after all the moisture (water) has been removed. Dry dog foods typically contain about 10% moisture; if the moisture was dehydrated away, the weight of the food would be different enough to increase the milligrams per kilogram numbers by about 10%. To use the Royal Canin Hepatic dry food example again, the dry matter value would be reported as 7.8 mg/kg DM (max).
• Caloric basis (kcals). Some companies report their nutrient values on a caloric basis. Copper would be reported as the number of milligrams of copper per 1,000 calories. Reported this way, the Royal Canin Hepatic dry food contains 1.9 mg/1,000 kcal (max). 

To review: These are three ways of expressing the same amount of copper in a given food. If you ask a pet food maker for a product’s copper content, you need to be able to recognize their answer as an as-fed, DM, or kcal value so you can make apples-to-apples comparisons to other foods. 

CANINE NUTRIENT REQUIREMENTS

The Association of American Feed Control Officials (AAFCO) is the organization responsible for establishing the nutritional standards that legally define “complete and balanced diets” for dogs and cats in the U.S. These standards are comprised of minimum values for each of the nutrients currently known to be required for dogs; they also include maximum values for a few of the nutrients known to be harmful to dogs if fed in excessive amounts. (AAFCO does not publish or attempt to guide pet food makers as to “ideal” or target amounts of any nutrients.)

These standards are published in tables called the AAFCO Dog Food Nutrient Profiles. There are two tables, with the required nutrient values expressed by dry matter in one and by calorie content (kcal) in the other. Each table contains a column with nutrient values for adult dogs (“adult maintenance”) and one for “growth and reproduction” (meaning puppies and pregnant and nursing mothers). 

Here are AAFCO’s minimum requirements for copper, for growth and adult maintenance, expressed on a dry matter and caloric basis: 

LOW COPPER DOG FOOD DIETS

Prescription diets are formulated to help manage a specific health condition. Sometimes this calls for certain nutrients to be included at levels that are above or below the legally required amounts – so much so that the product may not meet the AAFCO requirements. (That’s why they are sold by prescription only; dogs without the condition for which they are formulated could potentially develop a deficiency or excess of the nutrient/ that are out of the legal limits.) 

The treatment for dogs who have been diagnosed with CAH includes a diet that’s especially low in copper, as well as medicines that help the dog’s liver rid itself of its abnormal accumulation of copper. 

To our knowledge, there are only three companies that make low-copper dry food for dogs who have CAH (Just Food For Dogs makes a fresh-cooked Hepatic Support diet). Two of these dry foods are prescription diets that also have very low minimum protein levels (around 14% as fed). The third low-copper diet has a more average amount of protein (26% as fed). These dry diets and their copper values are indicated in the white stripes in the table below. 

We’re not fans of the ingredients generally used in prescription diets (which always contain more plant-sourced proteins, food fractions, and by-products than we like to see). That’s why, in our opinion, the best dietary option for a dog who has CAH – or is a predisposed breed – would be a home-prepared diet that is made complete and balanced with a veterinary-formulated supplement called “Balance IT Canine -cu” (“cu” is chemistry’s abbreviation for copper, and the minus sign indicates that it contains no copper). Particularly cool: Balanceit.com features a recipe-generating tool that owners can use to create their own complete and balanced home-prepared diets. 

CHECK YOUR DOG’S DIET

Sadly, we can’t count on many pet food manufacturers – not even those who make copper-restricted dog foods! – to be immediately transparent about the amount of copper in their foods. Even the companies that make copper-restricted diets often fail to publish their products’ copper levels on their websites! Fortunately, they do respond to inquiries. 

We checked the websites of all the companies whose products are presently on our “Approved Dry Dog Foods” list. Just 19 of them (a little less than one-third of the companies on our 2022 list) provide nutrient analyses that include copper values for their foods on their websites. We’ve listed a few random sample products and their copper values in the table below.

Ask the makers of your dog’s food about the copper content in their products, especially if your dog is at higher risk of CAH. If his food contains more copper than the FEDIAF maximum (28 mg/kg), we recommend changing foods to one with less copper. And regardless of breed, switching to a food with a copper content that’s closer to the minimum allowed seems wise.

Copper content in a random sample of dry dog foods (products in orange rows are low-copper foods)