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Linking Diet to Dilated Cardiomyopathy (DCM)
By Vivian Ojeda
Angell Cardiology Service
In July of 2018, the US Food and Drug Administration (USFDA) began investigating the potential link between certain diets and canine dilated cardiomyopathy (DCM), a cardiac disease characterized by decreased pumping function and increased heart size. Veterinary professionals are seeing an increased rate of DCM reported in dogs and cats eating diets with main ingredients such as exotic meats (kangaroo, pork, lamb), legumes (lentils, peas, beans), or potatoes, the main ingredients often found in diets marketed as grain-free.
DCM is an acquired type of heart disease, which means a patient is born with a normal heart, but develops heart disease later in life. The word “dilated” indicates that one or more of the four chambers of the heart are abnormally enlarged. The word “cardiomyopathy” indicates an abnormality of the heart muscle. In DCM, the heart enlarges and the walls of the heart become thin, resulting in a heart muscle incapable of pumping blood forward as strongly as it should. In addition, the electrical conduction system in the heart is often affected, sometimes resulting in life-threatening arrhythmias (abnormalities in cardiac rhythm). If left untreated, DCM can result in the development of congestive heart failure (fluid in the lungs, around the lungs, and in the belly) or sudden death.
Historically, DCM was linked to nutritional deficiencies and certain viral infections; with advancing medical skills and knowledge, these types of DCM have become relatively rare. Genetic transmission remains common in certain large and giant breeds (Doberman Pinschers, Irish Wolfhounds), and these breeds tend to display clinical signs in young adulthood or middle age. Starting in 2017, the veterinary cardiology community noted a distinct uptick in the number of DCM cases, and interestingly, these included breeds not previously reported. Included among the patients identified were mixed breed dogs, Golden retrievers, beagles, small breed dogs (Papillons, Bichon Frise, etc.), and cats.
Your Pet’s Diet
Cooperation between veterinary cardiologists, nutritionists, and the USFDA has confirmed that the increase in canine and feline DCM is linked to grain-free diets. The dogs and cats affected are often being fed boutique diets that contain exotic meats and are grain-free. On the ingredient list, the first 5 items listed are often non-traditional proteins (anything other than chicken or beef), potatoes or sweet potatoes, and legumes such as lentils or peas. Over twenty food brands have been identified, including home-cooked meals. While a small number of patients may require grain-free diets for management of chronic illness, most dogs and cats are being fed these diets as the result of heavy marketing and the misconception that grains cause illness.
While the link between DCM and grain-free diets has been confirmed, the exact cause is still under investigation. These diets may be deficient in an amino acid called taurine, or the components of the diet may not allow for appropriate taurine metabolism. This is of concern, as taurine is necessary not only for cardiac health, but also normal eye and brain function. Taurine levels in many patients are very low; however, only some patients improve with taurine supplementation. Other theories include a thus far unidentified toxin or lack of other essential nutrients.
Steps to Take
Many patients that develop diet-related DCM experience an initial period during which there are no outward signs of disease. This period may last for months or even years. Although symptoms are absent, cardiac testing performed during this time may reveal heart enlargement, pumping dysfunction, or the presence of arrhythmias. In moderate to severe disease, symptoms may include lethargy, exercise intolerance, coughing, labored breathing, and shortness of breath.
The initial tests utilized to diagnose diet-related DCM include chest x-rays and an echocardiogram (an ultrasound of the heart). This allows the cardiologist to assess the heart and determine if your pet’s diet is affecting cardiac performance. Next, blood work can be submitted to evaluate whether or not your pet is taurine deficient. From here, the best course of action and any necessary medications can be assessed to alleviate your pet’s symptoms. At home, begin to reconsider your pet’s diet. If your dog or cat does not have a specific medical reason for being on an alternative diet, then switching to a well-researched, quality controlled diet may be indicated. Diet change should always be discussed with your pet’s primary care provider. Your pet may be prescribed taurine supplementation; taurine supplement can be purchased over-the-counter, but dosing should be discussed with your veterinarian. In patients with confirmed diet-related DCM and/or taurine deficiency, cardiac follow-up is often required long-term. While some patients do improve with diet change, taurine supplement, and cardiac medications, others experience progressive disease.