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Tuesday, December 10, 2019

Should I Switch Diets? Grain-Free, DCM, and the FDA.

   For many pet owners, it isn't news anymore-- in June 2019, the FDA released on update on their investigation into canine dilated cardiomyopathy and grain-free diets, including the names of implicated brands. This press release quickly made national news and has been covered on virtually every major pet blog and news site. The issue still leave more questions than answers though, and concerned dog owners are asking themselves, their friends, and their vets... "Do I really need to switch diets?"

     The answer ultimately boils down to a cost-benefit risk analysis. Unfortunately, we do not have controlled, scientific studies validating everything. Science is a process, and our knowledge is ever evolving. Especially in a medical context, we often have to make these risk assessments with limited and incomplete evidence. There are some people out there, owners and pet professionals alike, that are refusing to recognize the risk of an otherwise unexplained development of dilated cardiomyopathy in dogs eating certain diets. While it's true that an exact etiology has not been identified for the arising cases of DCM, it is also true that there is substantial evidence to indicate a risk associated with certain diet types, as of the FDA's June update:

  • Of the dogs reported to the FDA so far (there are likely many more affected), 91% were eating grain-free diets (far greater than the proportion of dogs in the US eating grain-free diets, holding less than 50% of the market share), and 93% were eating diets that contain peas, other legumes, or lentils. Such a strong correlation rarely arises through chance, and as of yet these correlations remain the single greatest common denominator among all affected patients. 
  • Of the cases reported to the FDA, ~11% used kangaroo as a protein source, despite kangaroo representing less than 1% of the total market share.
  • While a confounding variable like age, breed, or regional differences could be at play, the cases reported to the FDA do not suggest that to be the case. Dogs of all ages, from less than a year to 16 years, have been reported. The range of weight is from 4 lbs to over 200 lbs. Over 50 breeds are represented in the complaints submitted as of June, when including "mixed" as a single breed. It's also worth note that "mixed" breeds are the second most common breed reported, despite being the least likely to share a common genetic predisposition.   
  • Cardiologists and owners are reporting improvement with diet change, perhaps the most compelling line of evidence that diet is at the root of this issue. While many of the dogs being treated receive taurine supplements, their initial blood work (taken prior to supplementation) often returns normal, or even high, taurine levels. Taurine is also not known to reverse DCM in dogs with a genetic breed predisposition. Many of the dogs treated also receive heart medications to support the function of their heart. These medications do not reverse heart disease. Generally, they slow the progression of heart disease, and patients remain on them for the rest of their lives. In cases of suspected diet-associated DCM, patients on a new diet are eventually able to wean off of medications as their heart function returns to normal. This is completely unheard of in genetic cases of DCM. 
For more owner stories and information on the issue of diet-associated DCM as it develops, consider joining the largest Facebook group dedicated to working with professionals and disseminating evidence-based information on the topic.   

    To return to risk analysis... If one finds themselves questioning whether or not to heed potential risks associated with certain diets, and switch even before a definitive causative mechanism is identified, they need only ask themselves what benefit they believe that the diet they're on holds in the first place. There is zero scientific evidence demonstrating grain-free diets to be superior or associated with improved health outcomes, a fact nutritionists have been pointing out for years.
     While allergies are cited as a common reason for the switch, less than 10% of dogs with  reported allergies have true food allergies, or about  0.2% of all dogs. Of those, allergies to grains are even more rare. Some owners are led to believe that their pet has an allergy to certain ingredients based on blood, saliva, or fur tests for dietary allergies. However, these tests are unreliable and inaccurate. One study even submitted fake samples (tap water, fake fur) and still received a positive allergy report.
     Ingredients such as corn, wheat, and soy are demonized as being "filler" ingredients, but they all contribute protein, fiber, and other dietary essential nutrients to a balanced diet. Corn is a potent source of linoleic acid. Soy, in particular, is comparably digestible to meat ingredients when processed appropriately, and boasts a diverse amino acid profile. Most grain-free diets do not avoid using similar plant-based ingredients (in the form of lentils, peas, and other legumes). However, the latter are poorly researched for inclusion in canine diets, and are now implicated in the development of the present DCM issue.

     The bottom line? There is enough evidence of risk associated with grain free diets to warrant concern, considering that if the risk is actualized, disease may go unnoticed until late stages, and the consequence is death. In the absence of any benefit from accepting that risk, yes, it is worth switching. 

The following resources may be helpful in selecting a new diet:

Infograph - Selecting a Pet Food

World Small Animal Veterinary Association Global Nutrition Committee Recommendations on Selecting a Pet Food


The Savvy Dog Owner's Guide to Nutrition on the Internet

Please leave your thoughts, questions, and concerns in the comments! Thanks for reading.