Diet, Dogs, and DCM

Food reviews have been a standard feature of WDJ for 22 years, so it’s not a surprise we are asked for dog food recommendations. The inquiries multiply whenever there is any bad news about dog food – and the ongoing mystery about a possible connection between dog diets and a serious heart disease, canine dilated cardiomyopathy (DCM), is definitely bad news.

Depending upon which news outlets you follow, you may be worried about feeding your dog a food that is grain-free, one that contains peas or other legumes, or one that is “boutique” or made with “exotic” ingredients.

If you haven’t been following any of the news, you can catch up by reading our in-depth article by nutrition writer Linda P. Case in the September 2018 issue (“The Heart of the Matter”) and the blog posts on August 2, 2018 (“Please Don’t Panic About the Grain-Free Thing”), August 9, 2018 (“Choosing Dog Foods After The Grain-Free Scare”) and July 16, 2019 (“Update on grain-free diets and DCM cases in dogs”). Suffice to say here that in July 2018, the United States Food & Drug Administration (FDA) announced that it was looking into reports of a possible link between DCM in breeds of dogs that are not considered at genetic risk of the disease and diets containing “peas, lentils, other legume seeds, or potatoes as main ingredients.”

A year later, the FDA published an update to its original announcement, which included detailed data about the cases they were investigating but still offered no guidance regarding how owners could feed their dogs in order to protect them from developing DCM.

We have been analyzing the data that has been released about the diets that were named in the 515 reports being investigated by the FDA. From this analysis, we have developed recommendations that can help you make feeding choices that we believe could protect your dogs from this disease. In the online version of this article, we have included links that will take you to more detailed explanations, should you wish to know more about how we came to our conclusions.

Before we go on, though, please note: Anything you read, including here and in articles written by veterinary nutritionists, is conjecture. No one knows for sure what might explain a link between certain types of diets and DCM in some dogs – or whether there even is a link – although we believe there is.

Is Your Dog at Risk?

It’s important to keep in mind that the vast majority of dogs who are fed the diets named in the FDA’s reports do not develop DCM! On the other hand, we know that there are more cases of DCM than those that have been reported (or even diagnosed). So how concerned should you be?

The risk of diet-related DCM is not the same for all dogs. Certain breeds of dogs (or lines within breeds) are susceptible to DCM due to taurine insufficiency, where the amount of taurine (or its precursors, methionine and cysteine) in the diet is enough for most dogs, but not for them. These breeds include the American Cocker Spaniel, English Setter, Golden Retriever, Labrador Retriever, Newfoundland, and Saint Bernard. If your dog belongs to one of these breeds, then you should be more concerned about what you’re feeding than the average pet owner.

Focus on Taurine

Taurine is considered an essential amino acid for cats, meaning that they require certain amounts in their diet to remain healthy. Taurine is not considered an essential amino acid for dogs because they are capable of making taurine out of two other amino acids that are considered essential in dogs: methionine and cysteine (also referred to as cystine). A series of studies that began in 1997, however, determined that taurine appears to be conditionally essential for some breeds of dogs, and some lines of dogs within certain breeds. In addition to the breeds named in our article, other breeds suspected of developing DCM associated with low blood taurine levels include the Dalmatian, Boxer, Portuguese Water Dog, Alaskan Malamute, Scottish Terrier, Irish Wolfhound.

For this reason, we were disappointed when the latest NRC guidelines were published in 2006 without adding a requirement for taurine. AAFCO finally updated their own guidelines in 2016 based on the NRC revisions, and also failed to require taurine in dog foods.

The European Pet Food Industry Federation (FEDIAF) has guidelines similar to those produced by the Association of American Feed Control Officials (AAFCO). FEDIAF standards for taurine’s precursors, methionine and cysteine, in adult dog foods are higher than AAFCO uses. European guidelines also have a separate category for dogs whose average daily energy intake is less than that expected by AAFCO (in other words, dogs who eat less food for their size need higher nutrient levels in that food). In our experience, most dogs eat less than what AAFCO assumes.

  • Adult dog guidelines for combined Methionine+Cysteine, expressed in grams per 1,000 kcal:
    • AAFCO: 1.63 grams
    • FEDIAF: 1.91-2.21 grams
  • Adult dog guidelines for combined Methionine+Cysteine, expressed in dry matter percentages:
    • AAFCO: 0.65%
    • FEDIAF: 0.76-0.88%

Because some dogs have problems creating enough taurine from its precursors, we would like to see taurine added to all foods. We appreciate the companies that are doing so and believe it to be one criterion you can use to identify responsible companies.

Other breeds are genetically prone to DCM that is not linked to taurine deficiency, including Boxers, Doberman Pinschers, Great Danes, and Irish Wolfhounds. These dogs may be at no greater risk of diet-related DCM, but since we don’t know for sure, owners may want to be more cautious with these breeds than with others.

Large and giant breed dogs are more susceptible to DCM than smaller dogs are. If you have a large dog, you should be more concerned about what you feed than those with small dogs. One of the factors that drew the attention of veterinary cardiologists, however, was seeing DCM in some smaller dogs as well, so even people with small to medium dogs may want to take precautions. Dogs who eat less than would be expected for their size (older or inactive dogs, or those who get too many calories from treats) also may be at increased risk of dietary insufficiencies, including taurine, which might help explain why some small dogs are affected.

Another risk factor is dogs who eat the same food for long periods of time. The initial FDA report stated, “Early reports from the veterinary cardiology community indicate that the dogs consistently ate these foods as their primary source of nutrition for time periods ranging from months to years [emphasis ours].”

The longer you feed the same food, the more likely your dog is to be affected by any nutritional deficiencies or excesses it contains. Those who rotate foods regularly, particularly those who rotate between different brands of foods with different primary ingredients, have less cause for concern than those who always feed the same food to their dogs.

Focus on Taurine

All of our recommendations are based on the assumption that the issue linking diet and DCM is related to taurine deficiency. There are two very good reasons for this. The first is the link between taurine and DCM in cats that was discovered in the 1980s. The second is the link between taurine and DCM in certain dogs being fed lamb and rice diets that first came to light in the 1990s. Because we know that a lack of sufficient taurine or its precursors can cause DCM in otherwise healthy dogs of all breeds and mixed breeds, it appears to be the most likely culprit in this current situation.

Some of the affected dogs in the FDA reports were found to have low blood taurine levels; however, the majority have normal blood taurine levels. Despite this, most dogs diagnosed with what is suspected to be diet-related DCM are given taurine supplementation, regardless of their taurine blood levels, as well as being switched to a different diet and prescribed heart medications. Some dogs improve, others do not. At this time, it’s impossible to know which factors lead to improvement and which are unnecessary.

Until we know more, our recommendations center on avoiding taurine deficiency by increasing the bioavailability of taurine and its precursors, even for dogs who do not appear to be taurine-deficient.

In general, we recommend avoiding the potential at-risk food categories identified below, or at least limiting them to less than half of your dog’s total diet (if you feed more than two types of food). If you cannot avoid these food categories, then we recommend that you look for foods with added taurine, and/or consider supplementing your dog with taurine yourself (see Supplementing Taurine, below), particularly if your dog is at higher risk of developing DCM, as described above.

SIDEBAR: Switching Dog Foods

Food Categories of Concern

We identified 293 different foods in the 515 reports being investigated by the FDA. We looked at the ingredients and guaranteed analysis of each of these foods, and, just as the FDA’s researchers were no doubt doing, looked for patterns or categories of products to study separately.

This Involves More Than Just “Grain-Free” Diets

We know that much of what you have read or heard before concerned “grain-free” diets, and we aren’t specifically making recommendations about this category of foods. Why? Because almost all of the reported grain-free diets fall into one or more of the categories of concern that we identified. Only eight out of 272 reported categorizable diets involved grain-free foods that did not meet any of the criteria we discuss in this article. Three of those were high in flaxseed, which is high in protein and fiber similar to legumes, and so might possibly lead to similar issues, though there are too few data to draw conclusions.

There is nothing about grains themselves that would protect against DCM. Grains are not a source of taurine, which is found only in animal products. While nothing is known for certain yet, we would bet our shirts that any issue with DCM has nothing to do with the absence of grains. We believe that the inclusion of legumes rather than the exclusion of grains is a more likely cause of a link between diet and DCM.

Adding grains to a grain-free diet won’t help to prevent DCM and could actually make the situation worse. Since taurine and its precursors come primarily from animal sources, replacing part of a complete diet with grains will decrease the amount of these amino acids in the overall diet. If you want to add foods to a commercial diet, always look to add animal proteins, such as meat, fish, and eggs.

We have long argued that there is no need to avoid grains in your dog’s diet unless your dog has a problem with a specific grain (food allergy or intolerance leading to itching and scratching or digestive upset). Our dogs eat rice, oatmeal, quinoa, barley, and other grains. We do avoid corn and wheat in non-human-grade dog foods, as feed-grade corn and wheat are more likely to be contaminated with molds and their toxins, which are not destroyed during the processing used to create pet food.

We identified four categories of products that might be linked to DCM in at least some dogs. All four start with the letter “L,” which can help to remember them.

Legumes. The FDA reported that 93% of all products involved in the reports they were investigating contained peas and/or lentils. Our analysis confirmed that 89% of the reported foods appeared to contain significant amounts of these ingredients (generally appearing before the first fat or in multiple combinations, sometimes with other legumes).

Lamb. Lamb-based diets are a known risk factor for taurine-deficient DCM. Our analysis found that more than 20% of the foods named in the FDA’s reports were lamb-based.

Limited-ingredient. We were a little surprised to find that limited-ingredient diets were also overrepresented in these reports and we therefore consider them another potential risk factor.

Low-protein. Diets with low protein levels are a known risk factor for DCM. Normal-protein diets that rely on plant proteins, such as from legumes, also appear to pose a higher risk.

Let’s look at each of these “L” food categories of concern.

Legume-rich diets

The FDA found that the vast majority of reported products (93%) contained peas and/or lentils. It seems likely that something about peas and lentils is impacting the availability of taurine or its precursors in the body. This could be due to incomplete plant proteins replacing animal proteins, or fiber from peas and lentils blocking absorption of nutrients, or some other anti-nutritional factors we don’t fully understand.

SIDEBAR: The Most Frequently Named Foods in FDA Reports

Peas are a relatively new ingredient whose popularity has exploded in the last 10 years. The fact that so many foods today contain significant amounts of peas (and other legumes) and the increase in the number of dogs that are reportedly developing DCM (especially those in categories not typically associated with this disease) seems significant. Remember, however, that correlation does not equal causation; again, we are speculating, as no one knows the cause at this time.

Legumes are defined as plants whose fruit (seeds) is enclosed in a pod. Legumes found in dog food include peas, lentils, beans (e.g., pinto beans, navy beans, kidney beans, lima beans, fava beans) and chickpeas (garbanzo beans). Pulses, another term commonly used, are the dry, edible seeds of plants in the legume family, including dried peas, beans, lentils and chickpeas. All pulses are legumes but not all legumes are pulses. Because dog foods may contain fresh peas as well as dried, we use “legumes” rather than “pulses” to define this category.

Fiber?

Note there is little correlation between the maximum crude fiber shown in the guaranteed analysis and the amount of dietary fiber in foods.

Pulses are high in protein and fiber and low in fat. High-fat legumes such as soybeans and peanuts do not appear to be involved in the DCM issue.

Bottom line on legumes: We recommend avoiding diets with legumes listed high in the ingredient list (before the first fat or oil) or that include several legumes, even if they appear lower in the ingredient list. If you do feed such a diet, it should not have any of the other “L” traits (be lamb-based, limited-ingredient, or contain less than about 30% protein on a dry matter basis [27% as fed, per the guaranteed analysis, for dry foods]). If you feed high-legume foods as a major part of your dog’s diet, look for foods with added taurine, or consider supplementing with taurine yourself.

Who Can You Trust?

Just because a company produces foods that were named in the reports being investigated by the FDA – even many reports – does not mean that company cannot be trusted. The FDA’s investigation found that nearly all the reported products were nutritionally complete based on current guidelines. Whatever is going on is not something that any company could have been reasonably expected to predict. We are far less interested in what has happened in the past than in how companies respond to the information that certain diets may be causing DCM in some dogs.

One of the things we expect responsible companies to begin doing right away is to add taurine to all of their high-legume diets. This is something that can be done quickly, safely, and with relatively little expense. The best companies will add taurine not only to high-legume foods, but also to diets that fall into other at-risk categories, including lamb-based diets, limited-ingredient diets, and diets that are relatively low in protein. ALL companies should already add taurine to their lamb and rice diets; not doing so is a red flag that the company is either unaware of the risk of taurine deficiency for some dogs eating these diets, or doesn’t care.

Pay attention to how companies respond to this issue. One of the ways to do so is to look for added taurine in the ingredient lists of their foods. Note that more than half the Purina foods reported to the FDA were lamb and rice diets without added taurine.

Another important factor that should help to determine how much you can trust a company is how they respond to your inquiries. Don’t put your trust in any company that does not respond to an inquiry, is unable to answer your questions, or refuses to provide the information you requested, especially when asking for nutritional information other than the guaranteed analysis. The best companies will be open and honest, and will make sure your questions are addressed properly, including referring them to the right person to respond when needed.

Lamb-based diets

Nutritionists have known for more than 20 years that certain breeds of dogs were prone to developing DCM when fed lamb and rice diets. Studies indicate this likely has to do with low bioavailability of taurine’s precursors, methionine and cysteine, in lamb meal. Responsible companies began adding taurine to their lamb and rice diets long ago.

Our analysis of foods named in the FDA reports found that more than 20% of these reports involved diets where lamb was the primary meat source; this included several of the foods with the most reports. The FDA’s analysis found lamb was the second-most common animal protein in reported foods (after chicken). Both of these appear to indicate that lamb is overrepresented in the named foods.

We expect that reliable companies already add taurine to their lamb and rice diets. We also would expect that by now they are in the process of adding taurine to their lamb-based diets that also contain legumes.

Bottom line on lamb: We advise avoiding lamb-based diets without added taurine. If you do feed a lamb-based diet, it should not be high in legumes, limited-ingredient, or low in protein. In addition, we would avoid all foods from any company that sells a lamb and rice diet without added taurine (if they hadn’t already been getting that right, we just wouldn’t trust them at all).

Note: We found several diets where lamb meal was listed second in the ingredient list, following a fresh protein such as beef or bison, which was usually the name used on the label. Because dry lamb meal weighs less than fresh meats, these foods contain more lamb than whatever was named first and would be considered lamb-based diets. Pay attention to ingredient lists, not just the name on the package!

Limited-ingredient diets

The first response from a veterinary nutritionist to the initial FDA report about a possible link between diet and DCM warned against “exotic” ingredients, but her list included both lamb and peas, neither of which would be considered exotic these days (see “We Won’t BEG, below). Instead, what we found was an overrepresentation of limited-ingredient diets, many of which contained no ingredients that most people consider exotic. Almost 40% of all reports received by the FDA involved limited-ingredient diets.

Supplementing Taurine

Not everyone can follow the dietary guidelines we offer. Dogs with severe food allergies or intolerances causing serious skin or digestive issues, and those with health conditions that require a specialized diet, may need to stay on their current diet, even if it is a limited-ingredient, lamb-based, high-legume, and/or low-protein food.

In these cases, we recommend supplementing your dog with taurine, a safe and inexpensive way to address at least one suspected cause of DCM. Typical dosages used for dogs known to have low taurine levels are 250 mg twice a day for small dogs (less than 25 lbs); 500 mg twice a day for medium-sized dogs (25-50 lbs), and 1,000 mg twice a day for dogs over 50 lbs. These amounts are safe to give to dogs with normal taurine levels as well.

It is unclear whether supplementing with taurine will help dogs who do not have low blood taurine levels or who remain on a high-legume diet, but it might help and should not cause harm. Because we don’t know for sure that it helps, however, taurine supplementation should not be used as a substitute for rotating through different foods for normal, healthy dogs.

Taurine can also be provided by adding fresh foods to the diet you feed your dogs. Note that taurine is found only in animal, not plant, products. Heart (e.g., beef heart, chicken hearts) has much more taurine than muscle meat or other organs. Dark poultry meat has 10 times more taurine than white meat, with beef, lamb, pork, and fish falling in between. Eggs are high in methionine and cysteine (taurine’s precursors) but have little taurine.

Both cooking and freezing decrease the amount of taurine in foods. The longer a food is cooked or frozen, the more taurine is lost.

Never feed more than about 20% of your dog’s daily calories in fresh foods without also adding supplements needed to make sure the diet remains complete and balanced.

The great majority of these diets included peas and/or lentils, but since that was true for all foods, not just limited-ingredient diets, it doesn’t explain why limited-ingredient diets were named in such a large percentage of reports.

We do not recommend feeding limited-ingredient diets to most dogs, as we believe feeding a variety of ingredients is more likely to meet your dog’s nutritional needs. If you feed a limited-ingredient diet due to your dog’s severe food allergies or digestive issues, avoid foods high in legumes or that are lamb-based or relatively low in protein.

As a general rule we also recommend that you avoid feeding most exotic proteins, anything other than beef, chicken, turkey, lamb, and maybe fish. Exotic proteins (such as kangaroo, venison, duck, bison, rabbit, and so on) should be reserved for potential food allergy testing and/or treatment in the future.

Bottom line on limited-ingredient foods: Until we know more, we feel that companies that make limited-ingredient diets should start adding taurine to these foods. If you feel you must feed a limited-ingredient diet that does not include added taurine, we would suggest supplementing your dog with taurine.

One additional note: Kangaroo was the protein used in the single food reported most often to the FDA – Zignature Kangaroo Formula. This food had twice the number of reports (44) as the next food, Acana Singles Lamb & Apple Formula (both limited-ingredient diets). While no research has been done that we’re aware of, it would appear that kangaroo, like lamb, may be associated with low taurine bioavailability.

Low-protein diets

Insufficient dietary protein is a known risk factor for canine DCM. Protein is needed to build lean muscle, and since the heart is a muscle, insufficient protein can also affect the heart.

We found only a small number of reports of very low-protein diets linked to DCM, but most had no other risk factors (no peas or lentils, not lamb-based or limited-ingredient). Several low-protein urinary care and renal prescription diets were reported to the FDA as being possibly linked to DCM. These diets range from 10.9% to 18.1% protein on a dry matter basis (10 to 16% as-fed).

In our opinion, these prescription diets are often fed unnecessarily. In particular, we do not recommend feeding low-protein diets such as Hill’s Prescription Diet u/d to most dogs prone to forming urinary stones, or feeding diets designed for dogs with late-stage kidney disease who are not expected to live very long to dogs with early-stage kidney disease, who may live for years.

We Won’t BEG

Even before the FDA’s first announcement was made public, veterinary nutritionist Lisa Freeman of Cummings School of Veterinary Medicine at Tufts University had posted an article online with her take on the issue, which was summarized right there in the title: “A Broken Heart: Risk of heart disease in boutique or grain-free diets and exotic ingredients.”

Dr. Freeman characterized diets with certain attributes as particularly risky: those that are “boutique, grain-free, or exotic ingredient diets,” or BEG for short – an acronym that quickly became popular and continues to be in wide use today.

There are several problems with this acronym. First, only the “grain-free” part is clear – and yet, grain-containing foods have also been named in some of the canine DCM reports that the FDA is investigating.

Dr. Freeman’s definition of “exotic ingredients” includes lamb, peas, and other grain substitutes. Even other veterinary nutritionists are confused by this category, describing it as “non-traditional protein sources.” While kangaroo, venison, and other exotic proteins appear in the table entitled “Animal Proteins in Diets Reported to FDA” in the FDA’s 2019 report, chicken, turkey, beef, and many other animal proteins commonly found in pet food also appear in the table.

Dr. Freeman uses the term “boutique” to target small pet food manufacturers, saying they “might be better at marketing than at nutrition and quality control.”

While we agree that some small pet food companies fit that description, there are others with more than adequate knowledge of nutrition and manufacturing to make great food. Also, there is nothing about the size of a company nor the length of its track record that automatically keeps consumers safe. The recent spate of recalls for Hill’s regular and prescription diets that were causing vitamin D toxicity – products that harmed and even killed dogs – proved this point.

Dr. Freeman and others have suggested that dog owners should buy food only from companies that conduct feeding trials – another way of recommending products from large companies, because feeding trials are so expensive that only the largest companies tend to have the money to pay for them. But feeding trials last just six months, not long enough for a diet to cause symptoms of DCM, and no testing for DCM or any other form of heart disease is done in feeding trials.

The FDA’s investigation has not identified any nutritional deficiencies in reported foods, so this issue cannot be blamed on a lack of nutritional knowledge or quality control.

The longer a low-protein diet is fed, the more harm it is likely to do. See the section entitled, “The Side Effects of Low-Protein Diets” in “Cast in Stone” (WDJ June 2010), and “When to Say No to Low-Protein” (“A Low-Protein “kidney diet” Is Not Always the Answer,” May 2005) for more information.

In addition, when we looked at all the named diets that did not include peas or lentils, we found a higher percentage of lower-protein diets, and some with mid-level protein but also with plant proteins in the ingredients, such as corn and wheat gluten meals, pea protein, and potato protein.

Plant proteins may be used to replace animal proteins, providing less taurine and its precursors and more fiber and other factors that may interfere with taurine absorption. Avoid foods that contain corn gluten meal or wheat gluten meal; these are poor-quality, incomplete plant proteins primarily found in lower-quality foods. Pea and potato protein may be acceptable if far down in the ingredient list, but we don’t believe they offer much if any nutritional benefit (we’d prefer to see added taurine instead).

Bottom line on low-protein: In general, we advise looking for foods with at least 23% protein DM (21% on the label, also expressed “as fed,” for dry foods), and preferably more. If you feed a diet that contains a significant amount of legumes, or that includes beet pulp or plant proteins, increase this minimum amount of protein to about 30% dry matter (27% as fed for dry foods). If you feel you must feed a diet with less protein than this, we advise supplementing your dog with taurine.

Additional recommendations

Beet pulp is known to interfere with taurine absorption. A 2016 study published in the Journal of Animal Science and Technology found that beet pulp may contribute to a decrease in taurine levels in dogs, both because it reduces protein digestibility (and thus the availability of the sulfur amino acids methionine and cysteine, taurine’s precursors) and because it increases fecal excretion of taurine.

Beet pulp is commonly used in dog foods as a source of fiber, but because of its effect on taurine, it would be safest to avoid this ingredient in diets with any of our “L’s” of concern (Lamb-based, Legume-rich, Low-protein, or Limited-ingredient).

The FDA also named potatoes and sweet potatoes as suspect ingredients, but we have our doubts about their potential contribution to diet-related DCM. Both of these ingredients have been used in pet food for much longer than peas and other legumes, and neither is used as an alternative to or replacement source of animal protein.

Our analysis supports this hypothesis: All of the reported grain-free dry foods with significant amounts of potatoes or sweet potatoes also fell into one or more of the other at-risk categories. If these ingredients were truly a risk factor, we would have expected to see many foods reported that contained potatoes or sweet potatoes but did not contain legumes and were not lamb-based, limited-ingredient, or low in protein. At this point we do not feel that the data support avoiding foods that contain potatoes or sweet potatoes.

One ingredient in this category concerns us, however: potato protein. We don’t like to see incomplete plant proteins used to replace better quality, pricier animal proteins, or to inflate the protein percentage on the label.

Remember the four “L’s”

Again, remember that we don’t know for sure if following our guidelines will help your dogs avoid developing DCM, but we believe they are your best option until more is known.

Four types of diets – those rich in legumes (peas, lentils, beans, chickpeas); limited-ingredient diets (especially those that use kangaroo); lamb-based diets; and diets that are low in protein or that rely too much on plant proteins – may be associated with low taurine bioavailability that could lead to DCM, particularly in certain breeds, large dogs, and those who eat less than expected for their size. We believe that limiting how much you feed of these types of diets, and/or supplementing your dogs with taurine, should help keep them safe.

FDA Updates

References

Veterinary articles on the recent investigation into diet and DCM in dogs

Taurine

Truth About Pet Food

WSAVA, Feeding Trials

Pet Food Industry

Hill’s Recalls

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