IS THERE A LINK BETWEEN GRAIN-FREE
DOG FOOD AND DCM?
US FDA launches investigation
In July 2018, the US Federal Drug Administration (FDA) alerted pet owners and veterinarians about reports of Canine Dilated Cardiomyopathy (DCM) in dogs eating pet foods containing peas, lentils, other legume seeds, or potatoes as the top 5 ingredients, and called for cases identified by veterinarians and cardiologists to be reported for investigation.
More than 90% of the reported products were labelled as “grain-free”, and 93% of reported products contained large amounts of “pulses” (e.g., peas, lentils, etc.), high in their ingredient lists. These include products labelled as both “grain-free” and grain-containing formulations.
FDA statistics and case studies:
Between 1 January 2014 and 31 July 2020, the FDA received more than 1100 case reports of diagnosed dilated cardiomyopathy in dogs. Some of these reports involved more than one animal affected by DCM, eating the same diet, from the same household. There were also approximately 20 cat reports, 13 of which died.
It’s not known how commonly dogs develop DCM, but these reports indicate a potential increase in cases of DCM in dogs not genetically predisposed, as many of these case reports included breeds of dogs not previously known to have a genetic predisposition to the disease.
Most dogs in the U.S. have been eating pet food without apparently developing DCM, but it should be considered that many cases of DCM might have been undiagnosed, misdiagnosed, or not reported to the FDA. The FDA states that they suspect cases are underreported because animals are typically treated symptomatically, and diagnostic testing and treatment can be complicated and expensive for owners. Veterinary medicine doesn’t have a widespread surveillance system, like the Centres for Disease Control and Prevention have for human health, and therefore the occurrence of different diseases in dogs and cats is not routinely tracked, and there is no measure of the typical rate of occurrence of disease apart from what is reported to the FDA.
How was Diet-associated DCM discovered?
Diet-associated DCM first came to light in cats in the late 1980s and in dogs in the mid-1990s, and since this time cases have continued to emerge. The link between DCM in cats and taurine deficiency was found in the 1980s and was resolved with the inclusion of taurine supplementation in food. In the mid-1990s, veterinary cardiologists investigating the role of taurine deficiency in dogs with DCM identified certain breeds with a potential genetic predisposition, for example, Golden Retrievers, American Cocker Spaniels, Newfoundlands, English Setters, Saint Bernards, and Irish Wolfhounds. Investigation found that many of the affected dogs were consuming kibble diets containing novel proteins and legumes, and many dogs had low plasma or whole blood taurine concentrations, although many cases did not fit this picture. Thus the link between taurine deficiencies is not as clear-cut as it was in cats, because the majority of dogs with DCM were not found to be taurine deficient.
Currently it seems that cases fall into 3 categories:
1. Dogs with DCM completely unrelated to diet (eg, breed-specific DCM);
2. Dogs with DCM specifically related to taurine deficiency
3. Dogs with DCM associated with separate, but yet unknown, dietary factors.
It is suggested that these dietary factors may include grain free food, but the extent of this issue is not clear, as not all cases have been confirmed to be linked to diet, and a true association has not been proven to exist. Thus, at this stage there is no clear answer to this issue, however the subject is undergoing continued investigation by the US FDA.
Before the July 2018 DCM Update, FDA/Vet-LIRN had tested multiple of the “grain free” products for minerals and metals (calcium, magnesium, phosphorus, iron, cobalt, copper, zinc, selenium, iodine) and amino acids including taurine, cysteine, and methionine. That product testing did not reveal any abnormalities. The average percentage of protein, fat, total taurine, total cysteine, total methionine, total methionine-cysteine, and resistant starch content on a dry matter basis (in other words, after removing all moisture content) were similar for both grain-free labelled and grain-containing products.
Dr Karen Becker and human Cardiologist Dr Steven Gundry filmed an interview with Social Media influencer Rodney Habib about this issue and postulated several theories about why these health problems are occurring with grain-free kibble:
Taurine levels could be depleted and/or become less bioavailable due to the high-starch content of legumes.
The problem might be related to the Maillard reaction between taurine and a carbohydrate during the extrusion process that depletes the digestible taurine level in the food.
The Maillard reaction is a chemical reaction between amino acids and reducing sugars that gives browned food its distinctive flavour. This occurs at temperatures between 140 to 165 °C.
Grain-free kibble is often higher in both whole carbohydrates and purified starches (e.g., pea starch, potato starch and tapioca starch) than grain-based kibble. As Dr Becker emphasises, the higher the starch level in any pet food, the less protein is included.
Grain-free kibble often contains rice bran and/or beet pulp as ingredients. These ingredients prevent bile acid recycling, leading to bile acid binding in the small intestine and then excretion. This causes taurine depletion by interfering with the enterohepatic recycling of taurine-conjugated bile salts and lowers total body taurine levels.
Legumes contain anti-nutrients (e.g., saponins, trypsin inhibitors, phytates and lectins) that may interfere with taurine absorption. .
What is "grain free" pet food?
Dry pet food, or kibble, is generally comprised of highly refined carbohydrates and/or legume meal, with some meat meal (rendered) and bone meal (sometimes, or calcium carbonate) as the main ingredients. Carbohydrates must be included at a high percentage of the kibble in order to form dough, and all ingredients in a kibble pet food need to be finely ground before mixing. The extruder is where the primary cooking phase for dry extruded pet food products occurs. The dough is cooked under high heat and high-pressure as it moves toward the open end of the extruder. At the end of the extruder the dough is forced through a “shaping die” and cut into desired shape. Kibble is dried in an oven until its moisture content is low enough to make it shelf stable. Vitamins, minerals, additives and preservatives are added after the kibble is cooked to provide nutritional benefits and to prevent the ingredients from oxidising and spoiling - often these are sprayed on as a final coating to the kibble.
Kibble that is “grain-free” has been marketed over the last decade or so as a “healthier” alternative to kibble containing grain. This is likely in response to consumer trends seeking dry food that does not contain grain as the carbohydrate component, as this may be linked to food allergies in their dog or may be due to general food trends, which have seen a backlash against high glycaemic grain and its link to obesity, inflammation and disease in human medicine. Thus, in recent years the pet food market has been flooded with dog and cat foods using legumes (or pulses, that is plants with a pod) such as pea, lentils, chickpeas, and/or soy as the main ingredients.
Why are legumes used in pet food for carnivores?
Legumes offer benefits to the pet food manufacturer:
They are cheap to grow and can be readily sourced as these are grown for use in intensive and livestock industries;
They provide a source of protein which is markedly cheaper than animal sources - they provide a cost effective way for manufacturers to boost the total percentage of protein in their formulas;
They contain high amounts of starch and thus can be used to bind the kibble ingredients into pellet form.
Many regard legumes as healthy for human consumption, as they are high in fibre and complex carbohydrates but low in fat. Whilst legumes do offer some health benefits, the down side is that they contain anti-nutrients (e.g., saponins, trypsin inhibitors, phytates and lectins). Phytates, and phytic acid, are antioxidant compounds found in whole grains, legumes, nuts and seeds. Legumes as they are included in kibble (that is, raw and ground into meal) are arguably not a species-appropriate food for carnivores as they lack phytase, the enzyme necessary to process phytic acid. This poses a problem, as phytates bind to certain dietary minerals including iron, zinc, manganese and, to a lesser extent, calcium, and slow their absorption. Ingredients for inclusion in dry food are extruded, the process of which has been reported to reduce the impact of legumes on large intestinal fermentation. However, the extent to which this is remedied is unclear.
Exactly how - or if - digestion of legumes is linked to cardiac disease and/or taurine deficiency is not clear at this stage.
Vegetable Protein vs. Meat Protein:
Vegetable protein provides a low value source of nutrition for carnivores. Unless specific percentages are included in the ingredients panel, a consumer will not know the protein content of their product in terms of animal and vegetable content. Plant protein provides an inferior source of amino acids for dogs and cats. Vegetable protein offers incomplete essential amino acids profiles, in particular taurine, which can only be naturally soured from animal protein. Meat, poultry, eggs provide biologically appropriate sources of amino acids for dogs and cats.
Important factors in assessing the value of protein content are the quality of the protein, protein digestibility and the proportion of amino acids to one another for protein synthesis. Dietary proteins that have ‘high biological value’ are those that contain a high content of essential amino acids and that are highly digestible. For carnivores, proteins with high biological value include muscle meat, organ meats (such as heart, kidney, liver and lung) and fish proteins. Furthermore, the best sources of taurine are animal protein sources, in particular the organs (e.g. heart, kidney, liver).
Recent research about DCM and legumes
A recently published feeding study indicated that feeding 420 healthy adult Labradors a diet containing kangaroo, peas, red and green lentils (60% total legume inclusion) for 30 days caused significant (p < 0.001) decreases in red blood cell counts, haematocrit and total haemoglobin and a 41.8% increase in plasma inorganic phosphate (compared to baseline results). There were also possible implications on taurine status, as indicated by reduced urinary concentrations of taurine. These blood and urine results were compared to 420 dogs diagnosed with DCM, matched for breed, gender and age, which revealed commonalities in these parameters.
What about ZIWI?
Firstly, ZIWI does NOT contain grains, rice or other carbohydrate fillers. All dried and caned recipes contain a minimum 90% meat, organs, bone, and New Zealand Green Mussel, on a dry-matter basis. This provides a diet high in animal protein of high biological value, and naturally contains enough taurine to meet the dietary needs of dogs and cats.
The air-dried recipes do not contain binders. To create a loaf like texture for the canned foods, which contain large amounts of meat, some type of binder is required. For lamb and beef recipes, plasma is used to bind the ingredients. For venison canned foods, a small amount of chickpea is used because venison plasma was unable to be sourced. The inclusion of chickpea is minimal - it has only increased the carbohydrate content by an average of 1.8% on an as-fed basis, and only half of the total carb content is from chickpea (the balance of the carbohydrate is provided by meat and kelp).
Interestingly, the FDA report notes a case in which an owner of a dog who was diagnosed with DCM switched the animal’s diet to ZIWI Peak and it subsequently resolved the heart disease symptoms.
Although the FDA investigation into diet associated DCM in dogs has not been able to draw any firm conclusions, it may be wise to consider recommending diets that contain little or no carbohydrates, particularly those that exclude legumes, lentils and potatoes. Instead, diets containing high quantities of animal protein of high biological value are preferred, and are carnivore appropriate.
 US FDA 2021, “Questions & Answers: FDA’s Work on Potential Causes of Non-Hereditary DCM in Dogs”, <https://www.fda.gov/animal-veterinary/animal-health-literacy/questions-answers-fdas-work-potential-causes-non-hereditary-dcm-dogs>
 Freeman, LM, Stern, JA, Fries, R, Adin, DB, Rush, JE, 2018, ‘Diet-associated dilated cardiomyopathy in dogs: what do we know?’ JAVMA, vol. 253, no. 11, p. 1390
 US FDA, 2019, ‘FDA Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy.’ FDA, Centre for Veterinary Medicine, <https://www.fda.gov/animal-veterinary/news-events/fda-investigation-potential-link-between-certain-diets-and-canine-dilated-cardiomyopathy#diet>
 Becker, K, Gundry, S, Habib, R, 2018, ‘Popular Grain-Free Pet Foods Are Causing Heart Disease.’ Mercola, <https://www.facebook.com/doctor.karen.becker/videos/popular-grain-free-pet-foods-are-causing-heart-disease/10156521657422748/>
 Lynch, G, n.d., ‘Beans – The New Superfood for Nutritional Support and Weight Management.’ Horn Animal Nutrition, < https://www.petfoodinstitute.org/wp-content/uploads/HORN-Animal-Nutrition-Bean-White-Paper-17_0414.pdf>
 Bakke AM, Wood J, Salt C et al. 2022. “Responses in randomised groups of healthy, adult Labrador retrievers fed grain-free diets with high legume inclusion for 30 days display commonalities with dogs with suspected dilated cardiomyopathy”, BMC Veterinary Research, vol. 18(1), pp 157. The study was funded by Mars Petcare and all authors are or were employees of Mars Petcare at the time that the studies were conducted.