Misinformation about the causes of DCM in dogs is still being spread at the expense of our patients. In this article, we will examine the current body of evidence for heart-healthy nutritional decision-making.

Over two years ago, veterinarians embarked on a turbulent journey in search of an explanation for the higher incidence of dilated cardiomyopathy (DCM) in dogs. Widespread confusion and assumptions that grain-free diets were the culprit influenced both pet owners and veterinarians. Even cardiology specialists began touting the unproven conclusion that diets with grains are protective and “heart-healthy.” The truth is very different, as we will discover in this article.

Grains are not connected to heart health

Research conducted by Dr. Joshua Stern, DVM, PhD, DACVIM, Chair of the Department of Veterinary Cardiology at UC-Davis, erroneously purported to conclude that grain diets or just adding grain to food is nutritionally protective against DCM in dogs. As a result, misinformation about grains, kibble foods, and raw diets continues to be propagated. While the research was interesting, the conclusions drawn from this limited study are rife with erroneous assumptions.

Pet parents of dogs, both with and without a significant risk of DCM, have changed foods to increase the grain content, believing that the simple addition of grain will prevent any future heart disease. This misguided and simplistic strategy should be discontinued if we value the health of our dogs and are availing ourselves of accurate, informed, nutritional data.

Nutrition education is limited in vet schools

We know that heart disease can be devastatingly life-threatening for a dog, and veterinarians take this very seriously. The sudden onset and swift progression of DCM tragically shortens lifespans and devastates families.

Sadly, veterinary school nutrition education is limited, and once we graduate, most of us work long hours. We don’t have time to do research ourselves, so we rely on the medical research community to provide data to support our arsenal of treatments. When the industry uses limited data research and inaccurate assumptions to create overreaching general recommendations that may not be fully helpful for our patients, we are at risk of doing the same. This seems to be the case in the DCM debacle.

How do we navigate conflicting information? 

Our best approach is to evaluate basic physiology and biology ourselves to find the “grain” of truth in this situation, which can lead us to a better conclusion for our patients and pets. We must focus on what we know, not what we have assumed. We need to allow the genetics, biology, and nature of the canine species to inform our conclusions.

We have access to good information about the pathways of important compounds that help heart function. We have evidence in dogs and other animals regarding possible genetic links, nutrient deficiency issues, microbiome challenges, anti-nutrient damage, and infectious agents that can all be implicated in heart disease. We know metabolic pathways require specific minerals and nutrients to produce important compounds for heart function and health. It is clear that while there is still no research to prove specific ingredients have a direct link to most DCM cases, it is also clear that there is no definitive research proving that nutrition is not a cause of DCM.⁴

Do kibble ingredients and nutrients contribute to DCM?

Biological, ancestral, and physiologic data suggest that feeding a steady diet of highly processed and heated pet foods could create a perfect storm that could contribute to DCM in dogs. But veterinarians are encouraged to believe the opposite is true. Processed foods are still recommended to patients with DCM while fresh foods are maligned.

It’s also worth noting that the grain-free trend in pet food production was likely a response to market demands for lower carbohydrate levels in foods, and not an actual need for the type of grain-free foods that resulted.

Is nutrition relevant in breeds more likely to have DCM? 

Even though some breeds are typically considered at risk for DCM, the relationship between diet and the genetic expression of DCM may still be relevant. It is possible that DCM breeds are more sensitive to the nutritional and other conditions that can create the disease in non-affective breeds.

Because we know the function of taurine in heart health is important, we can focus our attention on that nutrient. We know that, unlike cats, dogs can make their own taurine.

We also know that without enough copper, iron, methionine or cysteine, dogs can’t make taurine. If a dog is missing certain microbiota that make cysteine in the GI tract, he can become deficient in cysteine, which would consequently affect his taurine production. Without the proper natural precursors, can dogs make enough taurine for heart health?

It seems likely that a taurine deficiency in a breed prone to DCM might be doubly devastating to the heart. Perhaps this calls for heightened diligence in feeding fresh nutrient-dense foods to all DCM breeds. There is evidence that increasing levels of taurine and carnitine in the diet provides improvement for many cases of DCM.⁵

Size also matters

Compared to smaller dogs, large breeds synthesize 50% less taurine per unit of metabolic body weight.⁶ Large breed dogs are at higher risk of becoming taurine deficient. Obesity is also associated with lower concentration of taurine in animals.⁷ These physiological factors that increase taurine utilization in some dogs may make the endogenous synthesis of taurine insufficient to meet requirements. Dietary supplementation or fortification may be required, even though there is no minimum dietary taurine concentration according to current AAFCO recommendations.

Do other issues affect the taurine production line?

We know that taurine is lost through bile salt conjugation, especially if the dog is eating a high volume of starchy fibers, like beet pulp or rice bran. Studies show that the newly popular pet food ingredient, beet pulp, is even more closely associated with taurine deficiency than rice bran. The quantity of these fiber ingredients in the food is relevant.  While low fiber amounts can be healthful, too much will overly bind and remove taurine in bile salt conjugation, not allowing it to be recycled. Dogs will have an increased need for taurine if their diet is heavy in fibrous ingredients, especially beet pulp.

Highly processed kibble foods using poor quality meats, plant proteins, and excessive fiber are creating multiple areas of deficiency. However, grain-free kibble food does not categorize all grain-free pet foods. The deleterious cardiac effects of grain-free kibble foods are likely caused by the ingredients included in place of the missing grain and meat protein. This does not support the erroneous claims that just by adding grains, dogs can be protected from DCM. Nor does it support the claim that because fresh raw food diets have no grain, they are also implicated as likely to cause DCM.

In fact, the ingredients in fresh raw foods support healthy heart function and are not likely to contribute to DCM. In the two years since the Stern research, raw foods have not been implicated in increases in DCM. Given the research on relevant nutrients for healthy heart function, we are very lucky that there are more pet food options than just kibble diets, as both grain and grain-free kibble foods have been implicated in DCM cases.

Additional factors that may affect taurine bioavailability

Negative factors:

• Binder ingredients in kibbles, such as lectins, phytic acid, fibers, and polysaccharides, may inhibit taurine absorption, recycling or conversion. Phytic acid is found in beans, grains, nuts and seeds, and reduces the absorption of minerals. Lectins, found in beans, grains, nuts, seeds, potatoes and some dairy, mediate attachment and binding.⁴

• Cassava (tapioca) accumulates cyanide, causing increased demand for sulfur-containing amino acids during its detoxification, limiting the availability of amino acids used in the biosynthesis of taurine and carnitine. Peanuts, soybeans, sweet potatoes, broccoli and other cruciferous vegetables are also implicated.

• Heavy metals can negatively affect heart function.

• Tofu/soy based diets are low in sulfur-containing amino acids and devoid of taurine; they can contribute significantly to taurine deficiency and DCM.

Positive factors:

• Methionine/cysteine are needed for taurine production.

• Choline is used to make homocysteine, a precursor for methionine.

• Carnitine is important; deficiency can cause mitochondrial dysfunction in the heart muscle.

• Copper is needed for taurine creation.

• Vitamin E affects heart function.

• Selenium, not detectable in most kibble foods tested, is important for immune function.

Testing for taurine

Taurine, the nutrient most discussed in relation to DCM, may not be accurately measured using serum samples. Whole blood is likely to be the better measure of taurine levels, as platelets have been shown to contain taurine in measurable amounts. However, even measuring taurine with whole blood samples may not create an accurate picture in terms of the body’s needs.

We do not know how the blood taurine value corresponds to the actual amount of taurine doing its work intracellularly. Measuring intracellular taurine amounts would require biopsy and is unlikely to be popular or practical. Taurine is the most abundant intracellular free amino acid. One would expect most of the body’s taurine to be in the cells, which perhaps explains why in many DCM cases we have found taurine levels in blood to be adequate, when perhaps the cellular levels may be deficient.⁸

To avoid deficiency, it seems sensible to rely on practical diet information based on the nature and biology of the breed. Dogs would naturally obtain a good deal of taurine and its precursors from fresh meat diets. Even though they can make taurine, and AAFCO⁶ does not list it as an essential amino acid, dog food should likely still contain ingredients with taurine to seamlessly maintain cellular concentrations and decrease our concerns about DCM.

Dogs with IBD have low carnitine levels

Animals with IBD have been shown to have low carnitine levels from poor absorption.

When owners choose a grain-free kibble diet high in vegetable protein sources to help treat IBD, they are likely exacerbating an already low carnitine condition as well as creating a taurine deficiency in their dogs, which could contribute to the development of DCM.

Fresh raw food diets or homemade recipes created with a professional formulator are more effective options. They can help reflorinate the microbiota lost in IBD cases, and provide high quality digestible proteins with plenty of the sulfur amino acids, taurine and carnitine (and other nutrients), a low inflammatory carb percentage, moderate fiber, and healthy non-rancid fats.

Fresh, balanced, species-appropriate raw foods very unlikely to cause DCM

The fact that raw foods don’t have grains does not equate them to the DCM-related issues in dry kibble grain-free foods. Don’t focus on choosing between a dry kibble food that either has grains or is grain-free (two bad choices) – choose balance and freshness wherever possible:

• Taurine and carnitine are plentiful in meat-based diets.
• These diets contain copper and iron in appropriate forms for absorption.
• Increased plentiful microbiota are found in fresh raw foods.
• Recipes can vary in terms of Omega-6:3 ratios.
• Very few anti-nutrients will be found in fresh raw foods.
• Fiber and carbs are low in these diets.

Consider homemade diets

The most important decision we can make for our dogs is what we put in their food bowls.

Dog food formulators should have a deep knowledge of processing methodologies and nutrient interactions that go beyond meeting AAFCO nutrient profiles, and should not carelessly follow unsubstantiated market trends.⁹

Make sure your recipes provide nutrition for all aspects of canine health. Not all available recipes are fully balanced and complete, and most will not include nutrient data, especially for taurine and carnitine. Many recipes are general guidelines with room for big mistakes. 

Many people in the pet food industry are recognizing that the future of pet food is moving towards functional nutrition — ingredients designed and combined for optimizing the individual’s health needs. Using software tools like the Animal Diet Formulator™ (ADF) software has helped veterinarians, professionals, and even pet owners find and remedy deficiencies or excesses in recipes to improve pet health. Royal Animal Health University uses the ADF to teach veterinarians and technicians to evaluate and create recipes and diet plans. It is an unusually complete and useful nutrition tool with continually-updated data on nutrients like taurine and many others. 

Veterinarians should not just be looking at minimums; we should also be looking at the research for optimal levels of nutrients to keep up with current health concerns. The ADF performs important calculations to determine Omega ratios, and typical values for basic ingredients; it can even estimate nutrient values for many ingredients.

Creating recipes that accurately evaluate the nutrient levels of a cooked diet can be difficult. Cooking can cause nutrient degradation, loss, or even increases in some cases. The nutritional changes that occur when ingredients are cooked are included in the ADF data. If the final product is to be cooked before feeding, the recipe and nutrient data will reflect those nutrient changes. This may be critical as we consider the fragility of taurine in cooked diets for our DCM cases.

Always remember that food is medicine. While a good diet cannot cure all ills, a poor diet will always create problems. With proper nutrition, there is a strong tendency for health.

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¹July 2018 Report by the Federal Food and Drug Administration (FDA) and research conducted by Dr. Joshua Stern, DVM, PhD, DACVIM, Chair of the Department of Veterinary Cardiology at UC-Davis.

²Royal, B. Worried about grain-free diets & heart disease? Take heart! Innov Vet Care J. 2018;9:1:58-61.

³McCauley SR, Clark SD, Quest BW, Streeter RM, Oxford EM. Review of canine dilated cardiomyopathy in the wake of diet-associated concerns. J Animal Science. 2020; 98:6.

⁴Chelsea Kent, Food Regulation Facts Alliance, Hero’s Pets, Littleton, Colorado.

⁵Bélanger MC, Ouellet M, Queney G, Moreau M.  Taurine-deficient dilated cardiomyopathy in a family of golden retrievers. J. Am. Anim. Hosp. Assoc.2005; 41:284–291.

⁶AAFCO. Association of American feed control officials. Official Publication Association of American Feed Control Inc. 2018.

⁷Merheb M, Daher RT, Nasrallah M, Sabra R, Ziyadeh FN, Barada K.  Taurine intestinal absorption and renal excretion test in diabetic patients: a pilot study. Diabetes Care. 2007.  30:2652–2654.

⁸Huxtable RJ. Physiological actions of taurine. 1992. Physiol. Rev. 72:101–163.

⁹Mansilla WD, Marinangeli C, Ekenstedt KJ,  et al.Special topic: The association between pulse ingredients and canine dilated cardiomyopathy: addressing the knowledge gaps before establishing causation Journal of Animal Science. 2019;97:3:983–997.