Grain Free Diets for Dogs: Myths and Medical Issues

In recent years “grain-free” foods have taken over an increasing market share in the pet food industry, and many pet food companies have jumped on the marketing bandwagon implying that grain-free foods are somehow healthier for dogs.  The marketing is convincing but the science is not, and now there are concerns in the veterinary community that grain-free diets are related to an increase in one type of heart disease in dogs.

Dogs are not obligate carnivores.  Yes, they probably descended from wild meat-eating canine species such as wolves, but over the tens of thousands of years that dogs have lived among humans and become domesticated, their digestion and metabolism has adapted to an omnivorous diet, meaning they can eat both plant-based and meat-based foods.  Grains such as wheat, corn, rice and oats can be a part of a nutritious diet for dogs. We often hear from pet owners that they feed grain-free foods for allergies, but the science shows that dogs are much more likely to be allergic to animal-based proteins such as meat, fish, dairy or egg products.

The grain-free trend seemed to start after the 2007 pet food recall scare, where it was discovered that a toxic chemical called melamine was contaminating many brands of pet foods, causing kidney failure in hundreds of dogs and cats.  Melamine was illegally added by foreign suppliers to wheat gluten, which was used as a dietary protein source, to make it appear to be higher quality when tested. At that time the problem was discovered by veterinarians who noticed an increase in unexplained cases of kidney failure, many of which involved several animals in the same household eating the same diet. This led to huge industry-wide food recalls and an overhaul of quality control procedures for many of the large pet food companies.

Melamine contamination is no longer a problem, but somehow wheat and other grains have become an issue in the opinions of consumers.  There is certainly a trend in human nutrition towards gluten free and “Paleo” diets which exclude most grains, and the pet food companies are following that trend with products and marketing that follow consumer demand.

But this nutritional trend appears to have a downside for dogs.  In the past 2 years, once again veterinarians have noticed a potential diet-related problem: an increase in cases of a type of heart disease called DCM, or Dilated Cardiomyopathy.  DCM weakens the heart muscle, resulting in abnormal rhythm, heart failure and potentially death.  It is known to be inherited in several breeds including Doberman Pinschers, Great Danes, and Irish Wolfhounds, but now unexpected cases are being seen in dogs of many breeds, some very young.  Case reports often involve several affected animals in the same household eating the same diet.   The common thread appears to be grain free, exotic ingredient dog food made by small “boutique″ pet food companies.  Most of these foods include peas, chick peas, lentils, and potatoes as a carbohydrate source. A deficiency of taurine, (an amino acid found in meat products), is also known to cause DCM, but many of the dogs affected have had normal taurine levels.  The exact cause of this condition is still a mystery, but studies are underway to connect the dots.

In June 2019 the FDA issued an updated warning to consumers regarding the link between diet and heart disease in dogs, but no food recalls have occurred.  The FDA website lists the brands and flavors of foods most frequently associated, and there is a list of all the individual cases reported including breed, age, and diet fed to each dog.

The best way to diagnose DCM is imaging of the heart with ultrasound, especially if symptoms of lethargy, increased coughing, labored breathing, or fainting spells are seen, or if a heart murmur is detected by your veterinarian.  Affected dogs can often be managed with medications and some cases have resolved with a diet change.

If you are concerned: Don’t panic! There are probably hundreds of thousands of dogs consuming these types of diets and the reported cases of diet related DCM are relatively infrequent. Talk to your vet about diet recommendations for your dog to reduce the risk, and avoid marketing and social media trends when choosing a dog food for your companion.


For more information, contact your veterinarian, or go to:

Tufts Veterinary School Nutrition Service “Petfoodlogy” blog:  https://vetnutrition.tufts.edu/petfoodology/

Or visit the FDA website for data and updates on diet-related DCM: https://www.fda.gov/animal-veterinary/news-events/fda-investigation-potential-link-between-certain-diets-and-canine-dilated-cardiomyopathy