Where’s the beef?? Are grain-free diets causing heart disease in dogs and cats?

Last month’s hot-button media headline was no doubt the report from the FDA investigation into the potential link between grain-free diets and dilated cardiomyopathy (DCM) in dogs and cats. The following link is the latest report on the FDA’s findings since they launched their investigation in 2018:

June 27, 2019: FDA investigates possible grain-free diet and DCM link

The FDA investigation began after a large group of veterinary cardiologists had alerted the FDA to an increase in cases of DCM in dog breeds not genetically predisposed. The common thread in these cases was that the affected patients were eating boutique, exotic protein and grain-free (BEG) diets. The FDA investigation updates have stirred up a frenzy of online discussions and outrage from BEG diet supporters. Unsurprisingly, an onslaught of social media comments was unleashed, directing disdain at and mistrust of veterinary diets and veterinary nutrition knowledge. In light of this latest surge in online misinformation and confusion, I decided to write an article summarizing what we know as a veterinary/scientific community about the issue.

First, a word about dilated cardiomyopathy (DCM). DCM is a type of heart disease where the heart muscle cells become progressively destroyed or lose their function. This causes the heart's pumping chambers (ventricles and subsequently atria) to become thin and dilated and progressively weaker. There are multiple known causes and types of DCM: taurine deficiency in cats and dogs, genetic mutations within some breeds (Dobermans, Boxers, Irish Wolfhounds, Great Danes), drug related (chemotherapy drug doxorubicin), and viral induced (parvovirus).

A diagnosis of DCM is devastating for any pet owner. It can lead to abnormal heart rhythms, congestive heart failure, and even sudden death. My own Boxer, Ralphie, (also know as Ralphageddon, Ralphalfa-sprout, Ralphie-Roo, Poo-face) was recently diagnosed with arrhythmogenic right ventricular cardiomyopathy ("Boxer Cardiomyopathy"). He will need regular cardiac ultrasounds to see if he is among the small percentage of Boxers who will go on to develop DCM.

Let’s go back to the importance of taurine. Taurine is an amino acid that is crucial to myocardial health. In 1987, it was discovered that DCM in cats was associated with insufficient taurine in diets, and that the disease could be reversed if affected cats were supplemented with taurine. After that landmark study was published, taurine was required to be added to feline diet formulations. It is now rare to see taurine-deficiency DCM in cats, except those fed home-made preparations or commercial diets that are based on inadequate nutritional expertise or poor quality control.

Veterinary research suggests that although Golden Retrievers and Cocker Spaniels are not genetically predisposed to DCM like their Doberman counterparts, they may be genetically predisposed to taurine-deficiency. An additional dietary factor (grain-free and legume-containing diets) was recently discovered in Golden Retrievers diagnosed with DCM and low taurine blood levels. These dogs showed significant improvement in their cardiac ultrasound results and blood taurine levels after a change in diet and taurine supplementation. Most of the patients improved clinically and half of the patients were able to discontinue some medication. This means that unlike DCM in genetically predisposed dogs, the DCM in diet-associated cases can sometimes be reversed. What is puzzling to researchers and FDA investigators is that the blood taurine levels in other affected breeds (including mixed breeds) appear to be normal. In some of these dogs, a change in diet (with or without taurine supplementation) results in a reversal of the DCM. Possible causes for these non-taurine, diet-associated DCM cases are currently being investigated.

The FDA document summarizes some interesting findings from the recently reported DCM cases:

Most products fed were classified as grain-free, or containing peas and/or lentils or potato/sweet potato. No one animal protein source was predominant.
Most reports were for dry dog food formulations, but other types (raw, semi-moist and wet foods) were also represented.
The report published a list of the most commonly reported pet food brands that were named in the DCM cases. The top three brands include: Acana, Zignature and Taste of the Wild.
The FDA is working closely with the pet food industry to determine if changes in diet formulations, ingredient sourcing, or processing may be contributing to the spike in reported cases of DCM.

So why have grain-free pet diets become all the rage in the past ten years? A question like this opens a nutritional can of worms that even I don't have the stomach for. Suffice to say, pet food fads often follow human diet fads and humans are easily influenced by suave marketing techniques. Clever marketing + Dunning-Kruger effect + social media access = massive shifts in consumer ideology. The Dunning-Kruger effect is alluded to nicely by Charles Darwin in The Descent of Man, where he writes, “Ignorance more frequently begets confidence than does knowledge”. The following link describes this psychological theory in detail:

What is the Dunning-Kruger effect?

Current veterinary nutritionists report that most dogs and cats are very good at digesting and extracting the nutrients from whole grains. Whole grains provide important sources of protein, minerals, vitamins, essential fatty acids and fiber in diets, while keeping the fat and calorie content low. There is no current scientific research demonstrating that grain-free diets are healthier than diets containing grains. Some dogs may be allergic to specific grains (eg. wheat), however, these specific grain allergies are less common than allergies to animal proteins such as chicken, beef, dairy, and egg. In fact, food allergies are much less common than other types of allergies such as environmental and flea allergies. Gluten allergies are very rare in dogs, and have only been documented in some Irish Setters and Border Terriers. There are no documented cases of gluten allergy in cats. The following article provides an in depth look at the grain-free pet food craze:

How Americans decided dogs can’t eat grains

Back to my original question. Do grain-free diets cause heart disease in dogs and cats? Despite the concerning associations between grain-free diets and DCM, we have not yet established a cause and effect relationship. The number of diet-associated DCM cases remains very small. Between January 2018 and April 2019, 524 new cases of DCM were reported to the FDA (515 canine, 9 feline), some of which involved more than one animal per household. The American Veterinary Medical Association estimates that Americans own 77 million dogs and 58 million cats. As a veterinarian and pet owner, I stand by my belief that there is no one food type or even brand that is best for all pets. I can’t say that I ever jumped onto the grain-free bandwagon for myself (I don’t have celiac disease), and I don’t believe that owners need to be feeding grain-free diets to their cats and dogs. I will continue to support pet food brands that value quality control, thoroughly researched diet formulations, and knowledgeable technical support teams.

As the FDA continues its investigation, it is imperative that veterinarians obtain complete diet histories from their patients (cats and dogs) diagnosed with heart disease. If a patient is diagnosed with DCM and is on a BEG, vegetarian, vegan or home-prepared diet, veterinarians should be testing plasma and/or whole blood taurine levels. In addition, other dogs in the household that are eating the same diet should be screened for DCM. Possible diet-associated DCM cases should be reported to the FDA. If the patient is a Golden Retriever, the veterinarian or owner can also report the case to the Josh Stern Cardiac Genetics Laboratory. All dogs with possible diet-associated DCM should be supplemented with taurine, and a follow up cardiac ultrasound performed in 3-6 months.

Owners are advised to watch their pets carefully for clinical signs of heart disease: weakness, slowing down, exercise intolerance, rapid and shallow breathing, coughing, and fainting. Any of these symptoms warrant a prompt visit to a family veterinarian (where it is important to bring a list of everything the pet eats). Owners of possible diet-associated DCM pets are encouraged to save and submit all dietary components they are currently feeding (main food, treats, chews, supplements) and corresponding product labels. These owners are also advised to change their pet’s diet to one made by a well established manufacturer that contains standard ingredients (eg. chicken, beef, rice, corn wheat).

Sources:

Cherry K. What is the Dunning-Kruger effect? Verywellmind.com. June 14, 2019

Cummings Veterinary Medical Center at Tufts: Clinical Nutrition Service and Petfoodology website: www.vetnutrition.tufts.edu/petfoodology/

Freeman LM, Stern JA, Fries R, Adin DB, Rush JE. Diet-associated dilated cardiomyopathy in dogs: what do we know? Journal of the American Veterinary Medical Association
December 1, 2018, Vol. 253, No. 11, Pages 1390-1394

Kaplan JL, Stern JA, Fascetti AJ, Larsen JA, Skolnik H, et al. (2018) Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets. PLOS ONE. December 31, 2018, 13(12): e0210233

Mull A. How Americans decided dogs can't eat grains. The Atlantic. July 2, 2019

U.S. Food and Drug Administration website: www.fda.gov