FDA study on Dilated Cardiomyopathy in dogs

In July 2018, the FDA announced that it was investigating links between Dilated Cardiomyopathy in dogs and certain pet foods. This simply meant the FDA was interested in the links between non-hereditary dog heart disease and pet food. The focus was on “grain-free” pet foods although it wasn’t clear why the FDA did not include information on grain diets to make it a complete study.

Since then, pet parents on grain-free diets are understandably scared about whether what they are feeding will cause their dog to have heart disease.

However, the truth is that there was a lot more unsaid about the FDA investigation to dilated cardiomyopathy in dogs, which has caused panic. We’ll break down what DCM in dogs is and then provide some tips on how you could proceed.

What is dilated cardiomyopathy in dogs?

The College of Vet Medicine at Cornell University defines Canine Dilated Cardiomyopathy (DCM) as “a primary disease of cardiac muscle that results in a decreased ability of the heart to generate pressure to pump blood through the vascular system.”¹

Basically, the heart gets larger and the walls thinner so that pressure needed to pump blood elsewhere is reduced.

This means that dogs will likely have symptoms of lethargy, weakness or could collapse.

Other symptoms of canine DCM or dog heart disease could include “congestion of blood in the lungs (coughing, increased respiratory rate and/or effort, abdominal distention)”

Note that DCM is one of the more common heart diseases in dogs.

KNOWN facts about Canine Dilated Cardiomyopathy (DCM)¹

1. The definitive cause of canine DCM is UNKNOWN.
2. Dilated Cardiomyopathy in dogs MAY BE due to nutrition, genetic predisposition, infections or a combination of these.
3. Some dog breeds are more predisposed to DCM. If you have a Doberman Pinscher, Great Dane, Boxer, Cocker Spaniel there may be a higher likelihood of DCM. UC-Davis is looking into DCM related issues for the Golden Retriever.
4. Male dogs are more prone to DCM.
5. Vets use an echo cardiogram to definitively diagnose DCM.
6. Other tests that may help include X-Rays, which may show heart enlargement and electrocardiograms, which may be used to characterize heart rhythm.

DCM is usually an irreversible condition except for nutritional-deficiency DCM, which may improve with taurine supplementation.

Why aren’t we talking about DCM with cats?

Dilated cardiomyopathy (DCM) for cats is more rare today.² In the 1980s, thousands of pet cats were dying each year due to DCM.³ It wasn’t until 1987 that there was a link made between the nutritional deficiency of the amino acid taurine and these cat deaths. Basically, taurine is now considered an essential amino acid for cats as they cannot synthesize their own and has a requirement in AAFCO Nutrient profiles. DCM in cats now is uncommon since pet food manufacturers routinely add synthetic taurine to cat food.  

However, it is important to note that studying DCM in cats, dogs and other mammals is not new and has been happening for over 30 years!

“Before these observations, the dilated form of cardiomyopathy in cats, dogs, and other mammals was regarded by most investigators as a relentlessly progressive disorder resulting from inborn metabolic errors or a variety of pathologic processes, including viral myocarditis, immune-mediated myocardial injury, microvascular coronary artery spasm, or toxic insult to the myocardium.”⁴

Basically, our understanding of DCM is changing but we are not there yet.

Sources of Taurine for dogs and cats

“Taurine is found in large amounts in the brain, retina, heart, and blood cells called platelets. The best food sources are meat and fish.”

High amounts of taurine can be found in shellfish such as mussels, clams and scallops. You can also find high taurine amounts in dark meat of turkey and chicken.

What does the Association of American Feed Control Officials (AAFCO) say about taurine in pet food?

The AAFCO Nutrient Profiles is held as the ‘gold’ standard for how pet food should be made. If things do not meet AAFCO standards, pet foods are generally not considered complete or balanced. As such, both grain pet foods and grain-free pet foods formulate their foods to this standard and then have labs test them to certify they meet this standard.

The AAFCO dog food nutrient profiles establish no minimum requirement for taurine since taurine isn’t considered an essential amino acid for dogs,

What was the FDA Investigation into dilated cardiomyopathy in dogs or canine DCM?

The FDA announced in July 2018 that there may be a link between grain-free diets/ ingredients and DCM.

The FDA defined “grain-free,’ as pet foods “which contained a high proportion of peas, lentils, other legume seeds (pulses), and/or potatoes in various forms (whole, flour, protein, etc.) as main ingredients (listed within the first 10 ingredients in the ingredient list, before vitamins and minerals).”⁵

This definition would include dry kibble, raw pet food, semi-moist food and wet foods or canned food.

Based on that, the FDA aggregated the data and found the following grain-free pet food brands had the most frequently reported cases of DCM. Below is the list of which grain free dog foods are linked to heart disease.

3 alarming things to know about the FDA study on grain-free dog food & canine dilated cardiomyopathy

Alarming Point #1

The announcement triggered only pet owners feeding grain-free diets to report to the FDA. “The vast majority of the reports were submitted after the agency notified the public about the potential DCM/diet issue in July 2018.”⁵

• This limited the study and is a disservice to pet owners as it should have asked for ALL pet foods i.e. grain and grain-free diets.

• Grain-free diets constitute approximately 8% of all pet food sales i.e. take 2019 stats for US dry pet food sales of over $35 billion USD ^6&7 and divided by $2.9 billon USD ⁸. [Note that this is not exactly an apple to apple comparison. I could only find readily available stats for US dry pet food sales not total US pet food sales and the grain-free diet total was a Year to date till September 2019].

• By omitting pet food diets with grain, which constitute most of the market (92% of pet food sales) from the announcement was the FDA saying that grain diets are not linked to DCM?

Alarming Point #2

“The average percent protein, fat, total taurine, total cystine, total methionine, total methionine-cystine, and resistant starch content on a dry matter basis (in other words, after removing all moisture content) were similar for both grain-free labeled and grain-containing products.”⁵

• This means that in 2018, the FDA knew that all pet foods both grain and grain-free tested the same for amino acids.

Alarming Point #3

 “The FDA is continuing to investigate and gather more information in an effort to identify whether there is a specific dietary link to development of DCM.”⁵

Basically, correlation is not the same as causation. The FDA doesn’t know what the cause is of DCM in this case regardless of whether it is grain-free or not.

• A paper titled “Diet-associated dilated cardiomyopathy in dogs: what do we know?” mentions that multiple factors could be the reason that grain-free diets are being apparently linked to DCM. “Or, the apparent association may be spurious.”¹³

Note that prior to 2014, the FDA had only received reports of 21 sick dogs and an implication that kangaroo as a protein might be a problem for DCM. ” The FDA never told the public in July 2018 the Agency had only received reports of 21 sick dogs over 4 years .”

So far, we know that at best the FDA is working with a very weird limited scope. Is there a worst-case scenario? Yes. Blaming DCM on a type of pet food without having evidence just a hypothesis is shoddy.

What is the best way to classify canine DCM if your dog is diagnosed?

Let’s split the canine DCM cases up into 4 types based on the information we have so far.

Category 1: Dogs with a predisposition to DCM by breed.

Typically, DCM is known to affect larger dogs with a higher incidence of the disease in breeds such as the Doberman Pinscher, Great Dane and Boxer. Other breeds known to be susceptible to DCM include Irish Wolfhounds, Saint Bernards and Dalmatians.

“Occasionally, German Shepherd Dogs and some medium-sized breeds such as Cocker Spaniels, English Springer Spaniels, and Portuguese Water Dogs are also affected.”⁹

“However, specific genetic evidence for majority of cases is still lacking.”¹⁰ These are therefore inherited diseases based on in-breeding to attain certain breed standards or in some cases, mixing with breeds that already had a disposition to DCM. An example is the Irish Wolfhound. “Great Danes, Scottish deerhounds, Borzoi, and Mastiffs were crossed with the few remaining Irish Wolfhounds.”¹¹

Category 2: Dogs with DCM from a toxin/ infection.

This does not seem to be common. Some plants can supposedly trigger DCM and the other known toxin is the drug “doxorubicin (Adriamycin), an anti-cancer drug used to treat various cancers in dogs.”¹²

Category 3: Dogs with low plasma or whole blood taurine concentrations improving with Taurine supplementation

“Some breeds, such as American Cocker Spaniels and Golden Retrievers, may have a predisposition to taurine-deficiency, possibly through defects in metabolizing taurine. Many, but not all, cases that are supplemented with taurine will improve.”¹² It is not clear if other breeds may have this taurine deficiency or if it is caused by pet food.

Category 4: Dogs with normal taurine levels but still DCM

“On the other hand, some dogs that did not have low plasma or whole blood taurine concentrations also improved with a diet change and taurine supplementation.”¹³

A dog may fall into 1 or more of these categories. “Even dogs of breeds that have previously been found to be genetically predisposed to developing DCM, such as Doberman Pinschers and Boxers, should be tested because taurine concentrations have been found to be low in some of these dogs also.”¹³

What the FDA study seems to be trying to pinpoint is the cause of Category 3 and 4 as the amino acid profiles of all the pet foods including grain-free diets met the minimum AAFCO requirements for formulating dog food.

What is known about Taurine deficiencies in dogs?

It is no coincidence that of the Dog food formulations presented, the majority was from dry food. See FDA chart below.

High temperatures in cooking affect Lysine, an amino acid which is critical “for the synthesis of all proteins.”

High temperatures can result in Taurine deficiency that was fatal for thousands of cats in the 1980s and may be causing heart issues (dilated cardiomyopathy or DCM) in both cats and dogs. 

If you review our blog on how kibble is made, you will notice that high temperatures are required in the extrusion process needed to make dog or cat kibble.

In addition, there may be a possible link to DCM from the ingredients utilized in the manufacturing of kibble.

Nutritional deficiencies in taurine and carnitine have been known to cause diet-related DCM.

“The reasons for taurine deficiency in dogs are not completely understood but could be related to reduced synthesis of taurine resulting from an absolute dietary deficiency of the taurine precursors methionine and cystine; reduced bioavailability of taurine, methionine, or cystine in the diet; abnormal enterohepatic recycling of bile acids because of fiber content of the diet; increased urinary loss of taurine; or altered metabolism of taurine in the intestine as a result of interactions between certain dietary components and intestinal microbes.”¹³

Does raw pet food cause DCM?

There were 9 identified dog cases out of 515 dog cases of a potential link between DCM.

Looking at FDA granular data on raw pet food where it is the main food eaten, we’ll summarize the owner’s or vet’s comments provided to the FDA..

The list is arranged for ALL incidences we could find for both dog and cat and by:

PAGE # in FDA DATA – FOOD EATEN – DOG/ CAT- AGE (if known) – OWNER/ VET NOTES

Our notes are in blue where we can comment

1. Pg 22 Main food was Petcurean dry food. Boxer dog. Some Stella & Chewy on the side. DCM got better with taurine improvements. Not enough information to tell whether this falls under breed-specific or category 3 or 4.
2. Pg 23 NRG dehydrated raw food – mixed dog 8 years. Sudden decompensation of dog’s heart. Euthanized at the end. Not enough information to tell whether this falls under breed-specific or category 3 or 4.
3. Pg 26 Instinct the raw brand- domestic medium hair cat 8 years. Taurine supplementation helping. Possible cause rabbit protein. This may fall under category 3 or 4 and here an exotic protein is implicated.
4. Pg 27 Instinct the raw brand- Retriever Lab 3 years. Vet suspects nutritional DCM despite potential Breed links. Despite the dog being mixed with a retriever, there isn’t enough info provided.
5. Pg 31 Natural instinct specialty raw pet food Chicken- Sphynx cat 20 weeks. Not doing well after castration. DCM indicated. Really young. Not enough information presented. Although Sphynx are known to be at risk for a different cardiomyopathy.
6. pg 38 Primal Raw – King Charles Cavalier 1 year. Potential early DCM with vet guessing DCM from grain free diets. Not enough information
7. Pg 59 Instinct Original Grain Free Recipe- Irish Wheaten 9 years, female. Owner was advised to move off raw and given a sample of Science Diet d/d, which is grain-free but has not been implicated to date in diet-associated DCM. DCM may not be due to grain-free but something else in specific grain-free diets
8. Pg 59 Homemade raw diet – Schnauzer. Dog worsened despite cardioprotective drugs and passed away while running outside. Dog was a carrier for gene mutation associated with DCM, but carriers should not develop disease according to vet notes. Not enough information
9. Pg 75 Several Freeze-dried raw and dehydrated food – Whippet 3 years- Blood taurine levels are normal. Whippet is not known to get DCM. Switched to vegetarian plus homecooked. Not enough info on results.

There were 2 interesting cases on Pg 47 and on Pg 78, where pet owners decide to transition from a dry pet food to a raw diet. On page 47, the owner switches to raw dog food with fish oil and taurine supplementation. “At his most recent visit on January 25th, 2018 our cardiologist noticed a significant reduction in the size of his heart and an increase in the output of his heart -all great news.” https://www.fda.gov/media/128303/download

Pg 78, an owner transitions to raw diet for yorkie after finding DCM and is consulting with their vet for next steps.

Which grain-free dog foods were not affected by the FDA announcement on canine DCM potential link?

A lot of pet foods implicated i.e. grain-free diets promptly released 3^rd party studies or statements that showed that the taurine uptake from their foods met and surpassed the AAFCO standards.

We will only assess the grain-free foods that we would recommend as whole-foods based and meet/surpass AAFCO standards. We do not carry much kibble, so our list is limited to mostly freeze-dried raw dog food and dehydrated dog foods.

Nature’s Logic Dry Dog food kibble– Not implicated in the FDA study. Wholefoods based formulation. They do not use any of the grain-free ingredients/ legumes or potatoes. Here is their statement https://www.natureslogic.com/dcm/

Carna4 Oven baked Dry Food – Not implicated in the FDA study. Wholefoods based dog food with lower temperatures than extrusion. They utilize lots of meat and their legumes are lower in the ingredient list. Here is their statement http://carna4.com/wpress/wp-content/uploads/2019/08/DCM-Grain-free-Taurine-2019-Update.pdf

Primal Pet Foods – Implicated in 1 case. Wholefoods based freeze-dried formulation with exceptional frequency for testing their balanced formulas. You can find their statement here https://primalpetfoods.com/blogs/news/fda-update-to-dcm-investigation-what-we-know.

Steve’s Real Raw Pet Food – Not implicated in the FDA study. Wholefoods based freeze-dried dog food formulation. You can find their statement here https://www.stevesrealfood.com/2019/07/05/20509/

K9 Natural Raw Pet Food – Not implicated in the FDA study. Wholefoods based freeze-dried dog food formulation. You can find their statement here https://www.k9natural.com/dcm/

Stella & Chewy’s Pet Food– Not implicated in the FDA study. However, used as an intermittent freeze-dried dog food in the FDA granular data. We only carry their freeze-dried formulation so can speak to that. See here for their statement. https://www.stellaandchewys.com/blogs/addressing-the-dcm-concern/

Ziwi Peak Pet Food– Not implicated in the FDA study. Pg 53 of the FDA data showed that a dog with diagnosed DCM switched to Ziwi Peak and this resolved the case of diet-related DCM.  See here for their statement. https://www.ziwipets.com/blog/expert-advice/update-canine-dilated-cardiomyopathy-dcm

The Fallout of the FDA announcement on dilated cardiomyopathy in dogs

Unintended or not, the FDA announcement on a hypothesis of DCM linked to grain-free as fact, while knowing that both grain-containing and grain-free dog foods tested well for amino acids benefited ONLY grain-containing pet foods.

“Looking at the brands’ grain-free dry dog food sales from mid-July 2019 through the first week of October, in aggregate they decreased about 10%. At the same time, other dry dog food sales were increasing, rising from a down period in mid-2018 to slightly positive growth by early October 2019.”⁸ In addition, “the data also showed that their grain-free dog food sales had started falling in 2018 and throughout the first part of 2019, following the timeline of FDA’s previous DCM investigation alerts in July 2018 and February 2019.”⁸

What is the cause of your dog’s heart murmur?

“A heart murmur is an abnormal heart sound, usually heard by listening to the heart with a stethoscope.”¹⁴

There are different grades of heart murmurs and types. However, the loudness of the heart murmurs does not always correspond to the severity of the underlying heart condition. For adult cats and dogs, who have clinical symptoms of exercise intolerance, fatigue, pale gums, bluish tongue and/or coughing, have your vet check for a heart murmur.

There are many diseases that can result in your dog or cat’s heart murmur. For a puppy, small dog or cat, see here for more explanation. For a larger dog or the dogs, we discussed as pre-disposed to DCM, it may be a good idea to get regular testing.

Further testing such as chest X-ray, echocardiogram will be needed to have definitive diagnosis of the underlying issue with your pet’s heart.

It would be irresponsible for your dog’s heart murmur to be ONLY linked to diet-DCM without a definitive diagnosis as there are other causes of heart murmurs. This would be the same as having a fever and dry cough and automatically your doctor assuming you have COVID-19. It could be viral pneumonia or influenza. Without a test, your doctor should not be scaring you but rather walking you through possibilities of what could be causing your symptoms.

See a board-certified veterinary cardiologist to get better information on the underlying cause of your dog’s heart murmur condition.

5 Tips to mitigate the risk of your dog getting heart disease/ DCM

The number of dogs with DCM linked to dry dog foods was exceptionally high. The FDA is now following the path of checking whether there is a link between grain-free and DCM instead of all pet food specifically dry pet food and DCM.

DCM is a serious disease and should be taken seriously. However, it is important to know the facts above. Here are our tips to help you in this confusing time.

Breed-related canine DCM tips

1. If your dog falls within the breed categories, we suggest regular testing. It is important to remember that for these dogs, they may also suffer from low taurine concentrations and not just the breed-specific DCM.  

Diet-related tips to hopefully prevent Category 3 (low whole blood taurine concentration) & Category 4 (normal taurine but DCM)

1. Choose a whole foods-based dog food.
   • If you prefer dry dog food, opt for oven baked or in the case of better kibble brands look for pet brands that have a lot of protein as the first few ingredients. (Some pet foods supplement their protein by using legumes instead of good quality and quantity of meat.) Carna4 and Nature’s Logic are great dry food brands if you prefer dry dog food.
   • If you feed raw fresh pet food, opt for brands that use a lot of heart, muscle meat and organs (especially heart and liver). As lamb and duck were implicated. Look for a low-fat option in your raw pet food not only for the proteins we mentioned above as not all pet foods are created equal. Note that too much liver can cause hypervitaminosis A and if the raw food uses loads of liver and you feed your dog exclusively liver treats, you may be unwittingly causing a problem.
2. Rotate your proteins for pet food and if you want switch between pet food brands that meet high standards based on your research. Based on the FDA granular data, some grain-free diets were shown to reverse the diet-DCM e.g. Ziwi Peak so it may not be an issue of grain-free at all.
3. Add seafood to your pet’s meal once a week. An example could be mussels or sardines (don’t get the canned ones in oil). You can use Ziwi Peak or K9 Natural Freeze Dried as a meal topper or supplemental feeding if you don’t want to use it as your regular food due to budget constraints. These dog foods tend to have mussels and seafood in the formulation.
4. Add omega-3 fatty acids or ubiquinol as a preventative measure to your dog’s diet weekly.

If your pet is diagnosed with canine dilated cardiomyopathy or DCM

Your board-certified veterinary cardiologist will likely prescribe medication to help with the condition

The vet will likely supplement with taurine. Other supplements such as L-carnitine, omega-3 fatty acids and ubiquinol could also be part of the treatment protocol.

Send the information whether your pet food is grain-free or grain containing to the FDA to help them put together a better study.

Wishing you all the best!

References

1. Canine Dilated Cardiomyopathy (DCM) by Cornell University College of Veterinary Medicine https://www.vet.cornell.edu/hospitals/companion-animal-hospital/cardiology/canine-dilated-cardiomyopathy-dcm
2. Enlarged Heart (Dilated Cardiomyopathy) in Cats https://www.petmd.com/cat/conditions/cardiovascular/c_ct_cardiomyopathy_dilated?page=2
3. Myocardial failure in cats associated with low plasma taurine: a reversible cardiomyopathy. Pion PD, Kittleson MD, Rogers QR, Morris JG. https://www.ncbi.nlm.nih.gov/pubmed/3616607
4. Plasma Taurine Concentrations and M-mode Echocardiographic Measures in Healthy Cats and in Cats with Dilated Cardiomyopathy by D. David Sisson, DVM, David H. Knight, DVM,Cecelia Helinski, DVM, Philip R. Fox, DVM, MS,Betsy R. Bond, DVM, Neil K. Harpster, DVM,N. Sydney Moise, DVM, Paul M. Kaplan, DVM,John D. Bonagura, DVM, MS, Gail Czarnecki, PhD, and David J. Schaeffer, PhD  https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1939-1676.1991.tb00954.x
5. FDA Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy https://www.fda.gov/animal-veterinary/outbreaks-and-advisories/fda-investigation-potential-link-between-certain-diets-and-canine-dilated-cardiomyopathy
6. U.S. pet food industry – Statistics & Facts  https://www.statista.com/topics/1369/pet-food/#topFacts__wrapper
7. Global pet food sales hit $91 billion in 2018 BY DEBBIE PHILLIPS-DONALDSON 2019 https://www.petfoodindustry.com/articles/7899-global-pet-food-sales-hit-91-billion-in-2018
8. Pet food brands named by FDA in DCM alert see sales loss BY DEBBIE PHILLIPS-DONALDSON 2019 https://www.petfoodindustry.com/articles/8598-pet-food-brands-named-by-fda-in-dcm-alert-see-sales-loss
9. Dilated Cardiomyopathy in Dogs By Ryan Llera, BSc, DVM; Ernest Ward, DVM  https://vcahospitals.com/know-your-pet/dilated-cardiomyopathy-dcm-in-dogs–indepth
10. Dilated Cardiomyopathy in Dogs (DCM) https://vetspecialists.com/dilated-cardiomyopathy-in-dogs-dcm/
11. Genetics of Human and Canine Dilated Cardiomyopathy by Siobhan Simpson, Jennifer Edwards, Thomas F. N. Ferguson-Mignan, Malcolm Cobb, Nigel P. Mongan, and Catrin S. Rutland, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4525455/
12.  Dilated Cardiomyopathy in Dogs and Cats by Robert Prošek, DVM, MS, DACVIM, ECVIM-CA https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4952598
13. Diet-associated dilated cardiomyopathy in dogs: what do we know? By Lisa M. Freeman DVM, PhD; Joshua A. Stern DVM, PhD; Ryan Fries DVM; Darcy B. Adin DVM; John E. Rush DVM, MS https://avmajournals.avma.org/doi/full/10.2460/javma.253.11.1390
14. Heart Murmurs in Dogs by Cheryl Yuill, DVM, MSc, CVH; Updated by Amy Panning, DVM https://vcahospitals.com/know-your-pet/heart-murmurs-in-dogs