Dilated cardiomyopathy, or DCM, is characterized by an increased heart size due to weakened pumping ability of the heart muscle. In many patients, DCM eventually leads to heart failure and death.
Multiple studies have recently revealed a correlation between certain dietary ingredients and the development of DCM in dogs. In particular, an association between DCM and the feeding of grain–free diets is suspected, but not yet definitively proven.
In a recent article in JAVMA, specialists from veterinary colleges throughout the U.S. explained what is currently understood about diet-associated DCM. The FDA Center for Veterinary Medicine and Veterinary Laboratory Investigation and Response Network are also currently working with veterinary cardiologists and nutritionists around the world to identify the complex causes of this condition2.
The Relationship Between Diet & Dilated Cardiomyopathy
In the 1980s, an association between DCM and diet was first identified in cats affected with the condition3. Eventually, researchers discovered that taurine deficiency was the culprit, as cases could be effectively reversed with oral taurine supplementation and dietary modification.
Canine DCM is traditionally considered an inherited condition that predominantly affects certain large and giant dog breeds, such as the Doberman, Great Dane, and Irish Wolfhound. Unlike with DCM due to taurine deficiency, supplementing taurine in the diet is not an effective treatment for genetically caused DCM.
Since the mid–1990s, however, reports have been increasing in unlikely dog breeds, as well as mixed–breed dogs. In a worldwide survey of veterinary cardiologists, Ryan Fries, D.V.M., discovered more than 240 potential cases of diet–associated DCM over a 2–year period1. Most of the affected dogs were mixed–breeds, while frequently affected breeds included the Golden Retriever, Labrador Retriever, German Shepherd Dog and Cocker Spaniel.
“BEG” Diets
Eventually, researchers determined that many of the affected dogs were fed diets containing certain ingredients, often for months to years before developing clinical signs. Collectively, these were termed “BEG” diets, standing for Boutique (i.e., small manufacturer), Exotic protein sources, and/or Grain–free.
BEG and homemade diets have recently gained popularity in the pet trade. Many pet owners switch to BEG diets in the pursuit of wholesome, high–quality ingredients, and some grain–free diets are even marketed specifically for the management of certain health conditions, such as food allergy.
While BEG diets are appealing for well–intended owners, they often lack scientific support. Boutique diets made by small manufacturers are not always tested to meet the Association of American Feed Control Officials (AAFCO) standards or World Small Animal Veterinary Association (WSAVA) guidelines; therefore, they may be missing one or more important nutrients.
Exotic ingredients in diets fed to DCM–affected dogs have included novel meat sources (such as kangaroo, duck, buffalo and venison), flaxseed, fruit, probiotics, and starch and fiber derivatives. Grain–free diets frequently list peas, lentils, legume seeds or potatoes as the main ingredient.
Dr. Fries’ cardiologist survey revealed that many affected dogs had low blood or plasma taurine levels1. It’s important to note that not all dogs with diet–associated DCM were deficient in taurine. Instead, they may have been affected by other, currently unknown dietary factors. The FDA is currently investigating possible causes of diet–associated DCM, such as a deficiency or decreased bioavailability of another nutrient or, alternatively, the presence of a cardiotoxin in the diet2.
DCM In Golden Retrievers
A recent study suggests that Golden Retrievers may be particularly susceptible to diet–associated DCM. In the study, 24 client–owned Golden Retrievers were diagnosed with DCM and taurine deficiency, which the authors defined as <250 nmol/mL of taurine in whole blood4. Eleven of the dogs were severely affected and displayed signs of congestive heart failure that necessitated diuretic therapy.
At the time of diagnosis, all dogs were fed diets that did not meet AAFCO standards or WSAVA guidelines. Out of the 13 identified diets, 12 were advertised as grain–free, and 10 of these instead contained a legume as the main ingredient. After dietary modification and supplemental taurine, nearly all dogs showed significant clinical improvement, and congestive heart failure resolved in 9 of 11 dogs. This encouraging outcome suggests that diet-associated DCM is largely reversible in dogs when the underlying cause is addressed.
What to Do If You Have a Suspect Case
The FDA currently recommends reporting suspected cases of diet–associated DCM. Diagnostic workup should include a review of the brand, product and flavor of the main diet, as well as any treats and supplements. Look for these key factors: 1) BEG ingredients, 2) low protein, 3) high fiber, 4) vegetarian, 5) vegan, or 6) homemade diets.
Whole–blood taurine levels should be measured to examine the patient’s long–term taurine status. However, it is worth noting that Golden Retrievers with diet–associated DCM often maintained whole–blood taurine levels of 200–250 nmol/L, staying within the low end of the reference range for dogs4.
As recent studies suggest, dietary change and supplemental taurine are the mainstays of treatment, though it may take several months to observe patient improvement. Echocardiogram is the most sensitive method for assessing a recovering patient’s cardiac status during followup4.
Conclusions
The FDA and other study groups are still working to fully understand the relationship between dietary ingredients and the development of DCM in canine patients. Until more information is known, dietary assessment and case reporting should be performed for newly diagnosed cases of DCM, particularly for those dogs not belonging to high–risk breeds for genetic DCM. Veterinary practitioners can also help reduce the risk of diet–associated DCM by advising pet owners to only feed diets that meet AAFCO and WSAVA guidelines. +
References
1 Freeman LM, Stern JA, Fries R, Adin DB, Rush JE. Diet-associated dilated cardiomyopathy in dogs: what do we know? JAVMA. 2018; 253(11): 1390-1394.
2 US FDA. FDA investigating potential connections between diet and cases of canine heart disease. July 12, 2018. www.fda.gov/AnimalVeterinary/NewsEvents/CVMUpdates/ ucm613305.htm. (accessed December 13, 2018)
3 Pion PD, Kittleson MD, Rogers QR, Morris JG. Myocardial failure in cats associated with low plasma taurine: a reversible cardiomyopathy. Science. 1987; 237: 764–768.
4 Kaplan JL, Stern JA, Fascetti AJ, Larsen JA, Skolnik H, Peddle GD, Kienle RD, Waxman A, Cocchiaro M, Gunther-Harrington CT, Klose T, LaFauci K, Lefbom B, Machen Lamy M, Malakoff R, Nishimura S, Oldach M, Rosenthal S, Stauthammer C, O’Sullivan L, Visser LC, William R, Ontiveros E. Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets. PLoS ONE. 2018; 13(12): e0209112. https://doi.org/10.1371/journal.pone.0209112
