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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.


  1. Sure there's benefits to grain-free - no mycotoxins, aflatoxins, vomitoxins, melamine...also I've never seen a grain-free dog food use BHA, BHT or ethoxyquin as preservatives (the safety of them is highly debatable, and many anecdotal stories abound of seizures on foods with these ingredients. Plus grain-free foods don't use dyes, typically don't use unnamed animal sources (pentobarbital anyone?) and most grain-free use a higher meat % than grain-inclusive, which is where you find the taurine, carnitine etc. Corn and other grains spike glucose levels, cause ulcers in horses and cows, and don't contain as complete an amino acid profile as meat does. So yes, there are scientific benefits to grain-free.

    1. Hey Anon!

      Mycotoxins (including both aflatoxins and vomitoxins) are a risk in any commercial dog food, and are more likely to be present in grain-inclusive formulas ( but a responsible and reputable manufacturer will have quality control measures in place to reduce or eliminate the presence of such contaminants in their feed. As you can see in the linked piece, not all grain formulas have a presence of mycotoxins, and those that do fall below the accepted levels. An important principle in toxicology is that "the dose makes the poison." Many substances that are essential for life (such as Vitamin A) are also highly toxic at certain doses. However, the existence of an acutely toxic dose should not always lead one to conclude there are adverse effects associated with chronic, low dose exposure.

      In the case of these mycotoxins, we simply don't know if there are adverse effects to chronic exposure, and what those adverse effects, if any, may be. That is absolutely an area for research, but as it stands right now, the increased risk of low level mycotoxin exposure in grain-inclusive diets does not necessarily indicate a "scientific benefit" to grain free diets.

      It does serve as an example of why consumers should be discerning in selecting their pet food manufacturer, particularly in regards to quality control measures.

      BHA, BHT, and ethoxyquin are safe preservatives for dog foods. This is not up for debate, if we are talking about "scientific" benefits. That said, their absence is not an inherent trait of a "grain free" diet. Grain-inclusive diets can also utilize alternative preservatives.

      The presence or absence of dyes is not an issue of GI vs GF. Nor is the use of unnamed animal sources.

      If you have a source validating comparative meat percentages in GI and GF foods, as well as a supplemental source validating health benefits observed in dogs that eat a diet with a higher percentage of meat present within it, please do so.

      Dogs are not horses or cows, and this thread is not the place to get into explaining comparative physiology. The effect of corn and other grains on glucose levels is dependent upon the complete profile of the diet in question, as there are no commercial pet foods that consist solely of corn or another grain.

      Additionally, no one single ingredient holds a complete amino acid profile. Part of formulating a dog food is combining ingredients to create a complete and diverse amino acid profile, along with other essential nutrients, like dietary fatty acids.

      Again, there are no documented scientific benefits that a grain-free diet is necessary for dogs or superior for maintaining canine health. There are, however, prominent documented risks associated with feeding grain-free diets, particularly those high in pulse legumes. This likely boils down less to the lack of grains and more to the lack of research and expert input into these foods, but nonetheless, the diets do not appear safe for dogs as it stands right now.

    2. For consumers adamant on avoiding grains in their dogs foods, as well as some of the other concerns you've highlighted that are not intrinsically linked to grain-inclusive foods, they can still mitigate the risk of DCM by choosing a grain-free wet food from a reputable manufacturer, and checking to be sure that the food is free of pulse legumes and potatoes.

      For those insistent on a grain-free dry food, they are probably safest utilizing a grain-free food low in whole pulse legumes and from a reputable manufacturer, though it's still an unnecessary risk.

  2. Hey Anon!
    I'm sorry you feel that way. The group I linked is operated by several veterinarians and multiple other pet professionals. Additionally, there are a multitude of boarded veterinary nutritionists and veterinary cardiologists that contribute to the group! This includes advising the admin team and providing content for the evidence-based learning units within the group. Furthermore, this group has compiled data on case reports very similar to the limited release offered by the FDA. All cases within the group has been confirmed by review of veterinary records. As it serves as an invaluable resource for those looking to learn more about this very concerning, developing issue, I've provided a link.

    If you'd like to discuss any of the actual content of the article,I'm happy to amend any mistakes or clarify anything that doesn't quite make sense.

    Thanks again for taking the time to read and comment!



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