The association between taurine deficiency and dilated cardiomyopathy (DCM) has been a recognized problem for cats since the 1980s and for dogs since the 1990s. Taurine is an amino acid that is believed to play an important role in heart health including contractility of the heart and stabilization of cell membranes.
Taurine deficiency can occur for many reasons including a lack of dietary intake, low bioavailability, derangements in metabolism, or poor absorption from the GI tract. Animal muscle has the highest amounts of taurine compared to other components of commercial pet foods, however certain protein sources have higher levels of taurine compared to others. Plants have little to no taurine, and plant-based diets that include legumes have intrinsic factors that can result in depletion of taurine in dogs and cats.
Taurine-deficient DCM can develop in any dog breed, however certain breeds appear to be at greater risk than others including the Golden Retriever, Newfoundland, American Cocker Spaniel, English Setter, Labrador Retriever, among others.
A study of the Golden Retriever breed was recently published in which the authors sought to examine associations between specific diets, taurine deficiency and congestive heart failure.
Study Methods:
The methods for this multi-center, prospective, observational study included obtaining diet and medical histories, physical examination and echocardiographic data, as well as measuring taurine levels in whole blood, plasma, and serum.
A diagnosis of congestive heart failure was made if thoracic radiographs demonstrated evidence of cardiogenic pulmonary edema, or if there was evidence of pleural or peritoneal effusion on an ultrasound with concurrent evidence of DCM on echocardiography.
A low taurine level for the Golden Retrievers in this study was defined as:
The investigators compiled detailed information regarding the diets that these dogs had been consuming including the manufacturer, ingredients, caloric content, nutritional adequacy claims and method of substantiation for the claims. They evaluated whether or not the diet was touted as "grain-free," and whether legumes (pea, lentils, beans, chickpeas) were in the first five ingredients listed on the diet label.
The examiners also calculated the resting (RER) and maintenance (MER) energy requirements for each dog and determined whether the amount of food fed met those requirements.
Study Findings:
There were 24 dogs that met inclusion requirements for this study and a diagnosis of DCM based on their initial echocardiogram. Their mean age was 6 years + 3 years (range: 1-11 years), and the majority of dogs in this study had an ideal body condition score of 4 or 5 on a 9-point scale.
Twenty-three of the 24 dogs with taurine deficiency and DCM had been fed diets that were grain-free, legume-rich, or a combination of these factors. There were a total of 13 different diets documented. None of the diets were feeding trial tested for nutritional adequacy nor met WSAVA Global Nutrition Committee guidelines, however all were formulated to meet AAFCO guidelines. All diets were uncommon protein based, grain-free and 11 of the 13 diets were legume-rich. Brand and diets fed along with numbers of dogs diagnosed with DCM & low taurine levels included:
The length of time that dogs had consumed these diets prior to diagnosis was known for 22 of the dogs with a median of 814.5 days (range of approximately 6 months to nearly 10 years). When daily nutrition requirements were evaluated it was determined that all but for one dog was consuming less than their calculated MER.
Management of affected patients was not standardized and was at the discretion of the treating clinician. After the diagnosis of taurine deficiency and DCM, 21 of the 24 dogs were changed to a new diet. Seventeen dogs switched to a diet that included grain and 4 dogs switched to a different grain-free diet.
The mean body weight of dogs in this study was 32.4 kg + 4.7 kg (range, 22.9 kg - 45.3 kg). Taurine was supplemented at a median dose of 1500 mg BID (daily total dose ranged from 2000-4500 mg). Thirteen dogs were also prescribed L-carnitine supplementation at a median dose of 2000 mg/day (range, 500-6000 mg). Other medications that had been prescribed for some of the dogs included pimobendan (n=13), enalapril (n=7), benazepril (n=4), spironolactone (n=6), and diltiazem (n=2).
At the beginning of the study (baseline), 11 of the 24 dogs diagnosed with congestive heart failure were prescribed a diuretic (furosemide). The other 13 dogs were not prescribed a diuretic as they were considered to have occult DCM. By the end of the study (after diet change / taurine supplementation), of the 11 dogs that had been originally prescribed a diuretic: 5 dogs had discontinued the furosemide; 4 dogs had a reduction in the furosemide dose by 50-56%; 1 dog died from congestive heart failure and another was lost to follow-up.
Conclusions:
In this study, by 8 months follow-up, the vast majority showed significant echocardiographic improvement. Diet change and supplementation with taurine (with or without L-carnitine) resulted in significant improvement of echocardiographic parameters and normalization in whole blood taurine levels in all except for one dog.
Nine dogs had resolution of their congestive heart failure and 5 dogs no longer needed diuretic therapy. One dog in this study remained in congestive heart failure and this could have been attributed to a lack of diet change, owner compliance in administering medication, and/or response to therapy. As such, findings of this study are consistent with past studies that have demonstrated that taurine-deficient DCM may carry a good prognosis and that cardiac changes may be reversible.
Some dog breeds have a higher predisposition or risk for diet-associated DCM as compared to others. There may be genetic or metabolic reasons (or both) for this phenomenon.
Conclusions stated by authors of this study:
“Although a cause and effect relationship cannot be proven, the associations are concerning and warrant caution as well as future prospective studies. Assessment of taurine status of golden retrievers consuming similar diets may be indicated; however, adequate blood concentrations of taurine may be higher than previously recognized for some dogs. This data also underscores the immense value of obtaining complete diet histories in canine patients with cardiac disease.
Future, controlled, prospective studies of larger sample size are needed to determine if the clear associations identified in this manuscript represent a cause-and-effect relationship between DCM, taurine-deficiency, specific ingredients, and grain-free food varieties in general. Without such studies we cannot conclusively define which dietary characteristics are involved with the pathogenesis of this condition.“
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