Grains Are Not The Solution To Dilated Cardiomyopathy In Dogs

Dog owners are often concerned with what to feed their dog due to the concerns of DCM. There are many factors to consider when selecting an appropriate diet. Fresh food diets are often villainized because many do not include grains. However, recent studies provide data to guide dog guardians in making the best choice when feeding their dog.

The following topics are important in the discussion of DCM:

DCM in dogs is a medical condition where the heart becomes enlarged. It becomes more difficult for the heart to pump as it enlarges, and this can lead to congestive heart failure. The vast majority of DCM cases are hereditary and there are certain breeds which are known to be at high risk. However, hereditary DCM can be exacerbated by other factors, and a small percentage of cases may be attributed to non-hereditary factors entirely. The main causes of DCM include:

While DCM is not a new concern, recent reports have reignited interest that there could be a nutritional cause in some cases. In July of 2018, the FDA released a report stating that they were investigating a potential link between non-hereditary DCM and grain-free, boutique or exotic protein diets. The FDA urged pet owners and veterinarians to report cases of DCM in dogs with a suspected link to diet.

Many veterinarians and researchers began recommending that pet owners avoid grain-free, boutique, or novel protein pet foods despite no definitive evidence to support this switch.

The wording of this request by the FDA created a significant sampling bias. In studies or surveys, a biased sample occurs when the sample data is not random and therefore does not properly represent the larger population. The wording of the FDA’s report meant that potential non-hereditary DCM cases on grain-free or novel protein diets were more likely to be reported than any potential non-hereditary DCM cases on a grain-inclusive diet. This could have been prevented by requesting all reports of DCM within a certain time period regardless of the suspected cause, and without mentioning why the reports were being collected. 

The data submitted to the FDA thus far is rife with confounding factors such as concurrent diseases, incomplete diet history, age of the sample population, and unreported duration of the diet being fed. A majority of the reports include dogs breeds that are predisposed to heart conditions or of unknown mixed breed background. The FDA has stated that they are unable to investigate every report to verify or confirm the reported information and diagnosis.

There are several instances of conflicting information within the FDA data. While small boutique pet food brands were originally implicated in the first report, a breakdown of the data show that a large portion are from the 6 largest pet food manufacturers in North America. Additionally, the top seven proteins reported are chicken, lamb, salmon, whitefish, kangaroo, turkey, and beef which are not exotic proteins, except for kangaroo, as originally implicated. Currently, the FDA has received reports for both grain-free and grain-inclusive pet foods. 

In reviewing a set of data reports from the FDA for cases of DCM on a raw diet, very little is revealed. At first glance, several reports include “Instinct ‘the raw brand’”. However, this can be misleading as the actual product being fed is the dry food line. In several reports including premade raw brands, dry food was also being fed or the dog’s breed was well known for genetic heart conditions. There was one report including homemade raw food which was a schnauzer that also tested as a carrier for DCM. There were two dogs on the list that were switched to raw food after the diagnosis of DCM. One dog showed immediate improvement while the other did not provide an update.  

In addition to the FDA data, much of the recent research on nutritional DCM in dogs also contains sampling biases, confounding variables, inconsistencies in sampling parameters, known genetic predisposition in certain breeds, and lack of complete data for case studies. An in depth research review was published here in the Journal of Animal Sciences. 

As of December 2022, the FDA has stated that they will be discontinuing public reports on DCM until there is meaningful scientific information to share. They also state “while adverse event numbers can be a potential signal of an issue with an FDA regulated product, by themselves, they do not supply sufficient data to establish a causal relationship with reported product(s)”

There are multiple nutrients that play a role in cardiac function and heart health. While a nutritional cause for non-hereditary cases of DCM currently remains unproven, there are certain nutrients of note in relation to the subject of heart health and DCM.

Taurine is an amino acid that is important for cardiovascular health as well as other purposes. Dogs synthesize taurine in the liver from the precursors methionine and cysteine. Therefore, taurine is not currently considered a dietary essential nutrient for dogs like it is for cats. However there are medical conditions and genetic co-factors that can increase a dog’s need for taurine.

Taurine is degraded by heat and oxidation. Therefore, the high heat processing of commercial pet food will reduce taurine concentrations.

Methionine and cysteine are amino acids that are a dietary requirement for dogs in order for them to biosynthesize taurine. If these nutrients are low in the diet, this may affect a dog’s ability to produce enough taurine. Additionally, there is some evidence to suggest that larger breeds of dogs may have a lower biosynthesis rate of taurine than smaller dogs. Therefore, some breeds may have a higher dietary requirement than normal for methionine, cysteine and/or taurine.

Based on the nutritional data available, kangaroo meat is low in the amino acids methionine, cysteine, and threonine. The amount of amino acids is dependent on the subspecies of kangaroo. However, a kangaroo based diet combined with other factors such as genetics, nutrient inhibitors, and excess fiber can present nutritional deficiencies if not properly addressed. 

Combining kangaroo with other protein sources will increase the essential amino acids in home prepared diets. Heart muscle meat from a common protein (such as beef, pork, or lamb) is recommended as the additional ingredient to pair with kangaroo. This is because the heart provides more methionine, cystine, and threonine per gram in comparison to other options.

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Dietary fiber in moderation has multiple benefits. However, excessively high levels of fiber can decrease protein digestibility in the hindgut and have anti-nutritive effects. Since amino acids are proteins, excessive fiber can potentially hinder absorption of the amino acids crucial for heart health as well as other essential nutrients. 

Most commercial dry and canned pet foods are extremely high in fiber due to the high amounts of plant ingredients used, and this issue is not limited to grain-free foods. Grain-inclusive foods typically include just as much fiber as grain-free dry or canned pet foods.

There are several essential nutrients that play a role in heart health, and deficiencies of said nutrients have been associated with myocardial damage. However, it has not yet been determined if these nutrient deficiencies contribute to the development of DCM.

Regardless of the underlying cause, pets diagnosed with DCM or other heart conditions should consume a balanced diet with specific modifications to decrease inflammation and hypertension associated with the disease. It is recommended to work with a certified nutritionist when implementing a therapeutic diet.