Dilated cardiomyopathy (DCM) is a disease characterized by an enlarged heart as a result of compromised function of the heart muscles. The etiology (manner of causation) of the disease is not fully understood yet and, in many cases, the cause of the disease phenotype cannot be identified. A number of studies have been conducted in which a variety of etiologies have been noted. The most commonly attributed cause of DCM is genetics, with specific genetic mutations being identified in Doberman Pinschers, German Shorthaired Pointers and Boxers. Other breeds in which inherited DCM has been recognized are Great Danes, Newfoundlands, Irish Wolfhounds, Saint Bernards, Cocker Spaniels, Golden Retrievers, Bulldogs, Airedale Terriers and Scottish Deerhounds. More research is required to identify specific genetic mutations associated with DCM in these breeds.
Peer reviewed, published scientific studies have identified non-genetic causes of DCM including myocarditis (inflammation of the heart muscle due to infection), hypothyroid disease, tachycardia (rapid heart rate) and nutrient deficiencies or nutrient imbalances.
An attempt has been made to associate certain categories of diets and diets with certain characteristics to canine dilated cardiomyopathy. The fact is that there is a much more complicated relationship between food and DCM. A broad category like grain free or boutique cannot be linked specifically to any health condition simply because there is so much variety within categories like this. Even characteristics of a food such as containing legumes or exotic proteins is much too broad of a characteristic to be able to make causative conclusions.
Nutrient imbalance and deficiency
Taurine and carnitine have both been linked specifically to dilated cardiomyopathy. These are both non-essential nutrients for dogs because they can be manufactured endogenously in the liver. The synthesis processes can be disrupted when dogs are fed diets that are low in total protein content or low in essential amino acids. Diets high in fiber can limit protein digestion and absorption which in turn can lead to deficiencies of essential amino acids, which affects production of taurine and carnitine. Other nutrients involved in the synthesis include iron, selenium, zinc and niacin; these nutrients have yet to be investigated for potential links to disease development.
Nutrients that could potentially affect development of canine DCM, but require further investigation, include vitamin E, potassium, choline, thiamine and copper.
In some studies, improvement was observed after a diet change, but other treatments were also administered, including taurine and/or carnitine supplementation and drugs such as inotropic agents, diuretics, ACE inhibitors and calcium channel blockers. It is impossible to determine causation or even correlation with so many confounding variables.
One of the only research projects done in a controlled environment with proper experimental methods is a peer-reviewed, published study done by the university of Illinois. Dogs were fed either a diet containing 45% legumes, or a diet composed mostly of animal protein. Over 90 days, there was no significant difference when comparing amino acid and taurine status of the two groups. More detailed investigation is still required in order to make concrete conclusions.
Current FDA reports include sampling bias, small sample size, incomplete information about the sample population, confounding variables, lack of standardized measurements and conflicting information. It is not a scientific study, rather a collection of information submitted by pet owners.
The FDA sample population includes an over-representation of specific breeds such as Golden Retrievers representing 19% of all dogs in the report. Of all the dogs included with breeds named, 40% are breeds with a known genetic predisposition to developing DCM so it is not likely these cases are related to nutritional deficiencies, at least not exclusively.
Many of the reports were incomplete, missing the dog’s breed, age, weight, and not including complete diet history and medical records. The majority of reports included no analysis for taurine deficiency or any other nutritional deficiency. Some reports did not even include a diagnosis of DCM.
There was no control for confounding variables like treats, medication, supplements or other health conditions. In fact, the FDA Vet-LIRN report stated that 44% of the 202 dogs who were diagnosed with DCM via echocardiogram, also had documented concurrent medical conditions.
The FDA report states that boutique foods made by small manufacturers increase risk, but nearly half of the dogs in the report were consuming foods from the 6 largest pet food manufacturers in North America. It is also suggested that diets containing exotic proteins could be contributing, yet 76% of the diets named included typical pet food proteins such as chicken, lamb, salmon, whitefish, turkey, beef and pork. It is stated that grain free diets and diets containing legumes are related to DCM because the majority of the dogs in the report were eating this type of food, but this is what was specifically asked for, and no control data was collected to compare it to.
Based on the current scientific evidence available, there does not appear to be a link between “BEG” diets and dilated cardiomyopathy. More controlled research is required in order to obtain a better understanding of the disease and how it is related to genetics, metabolism and nutrition.
Without definitive conclusions from research, the best recommendation we can make is to provide variety in the diet of dogs. Any potential negative effect of a diet is compounded when the same diet is fed every day for every meal for an extended period of time. Rotational and combination feeding can mitigate the risk of continuous nutrient deficiency or adverse effects of specific nutrients or nutrient balances.
Click the link below to read a previous blog about combination feeding.
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