Grain-free diets: Fabulous, fad, or folly?

Finding the perfect diet for health, longevity, and fitness has long been an obsession of Americans. Paleo, gluten-free, and “clean eating” are just a few of the more recent trends to hit the billion-dollar diet industry, with entire aisles of the grocery store devoted to certain types of foods that are purported to have almost miraculous powers of healing and regeneration. Inevitably, these trends spill over into the pet food industry. About 10 years ago, dog and cat foods labeled “grain-free” began showing up on the shelves of pet food stores. In 2017, 43% of pet specialty foods were grain-free. After all, if it is supposed to be good for us, it must be good for our dogs and cats, right?

Not so fast. There are major differences in the nutritional requirements of dogs, cats, and humans. There are a lot of foods that are good for humans that are actually not nutritious or even toxic for our pets. Some of these foods are showing up in grain-free, exotic protein diets. Additionally, the starchy carbohydrate substitutes for “grain” that are being added to these diets can be difficult for our pets to digest, leading to chronic diarrhea. In cats, replacing traditional grains such as corn or rice with starches such as potatoes can potentially lead to weight gain and a higher risk of diabetes. Many cat owners equate “grain free” with “low carbohydrate,” but some of the grain free diets have as many if not more carbohydrates that the more traditional diets.

The most troubling association that has arisen recently in regard to grain-free foods is a link to an increase in the incidence of a heart disease called Dilated Cardiomyopathy, or DCM. DCM is a disease where the heart becomes enlarged due to weakening of the heart muscle, making it unable to pump blood efficiently. Dogs with DCM often tire quickly, cough, or have rapid or labored breathing. The condition can also cause sudden weakness, fainting, collapse, and death. It is best diagnosed with an echocardiogram, which is an ultrasound examination of the heart.  

DCM is known to occur at higher rates in certain breeds of dogs, and in dogs and cats whose diet is deficient in taurine. Mainstream pet food companies have been adding taurine to their recipes for over half a century. It is unknown at this time what it is about the grain free exotic diets that may be contributing to DCM. What is known is that as of late August, the FDA had received reports of about 200 cases of dogs with heart disease potentially related to diet. The diets were those that listed potatoes or multiple legumes such as peas and lentils early in their ingredients. These are ingredients that are commonly used in foods labeled as “grain-free.”

Although the FDA has not yet recommended any recalls or advised any dietary changes for healthy pets, their investigation is in its early stages. Multiple brands are involved in the suspect cases. Not all grain-free diets are represented in the affected dogs. Researchers say that identifying grain-free diets as the source of the problem may be too specific. Dr. Lisa Freeman of Tufts University coined the term “BEG” diet, for boutique, exotic, and/or grain-free. This includes diets that have uncommon meats such as kangaroo, alligator, venison, bison, and rabbit. “We don’t know much about the nutritional value of these other protein sources like we do chicken and beef,” said Dr. Darcy Adin, a veterinary cardiologist at North Carolina State University who is part of a team that is investigating this issue. Adin notes that affected dogs could have a predisposition to developing heart disease on particular diets. Another possibility is that a relatively high content of legumes somehow interferes with digestion of other nutrients like taurine, which then leads to heart disease.

Many pet owners have been led to believe that grains such as corn or wheat are bad for their dogs. In reality, dogs can digest grains and starch 28 times better than their ancestor, the wolf. Whole grains have vitamins and minerals that are good for dogs. Many owners blame grains for their pets’ allergic skin disease. Food allergy is actually much less common in dogs and cats than environmental allergens such as fleas, mites, and pollen. Studies of dogs and cats with skin allergies have identified food as being a component in only about 10% of the cases. The most common sources of diet-based allergies were beef, dairy, and chicken, not corn or other grains. Additionally, if you suspect your pet has a food-based skin condition or gastrointestinal sensitivity to certain foods, the best course of action is to do a minimum two-month food trial with a hydrolyzed protein diet under the guidance of your veterinarian rather than experiment with exotic proteins and starches. Hydrolyzed protein diets take the guesswork out of a food trial, since the proteins have been broken down into small chain peptides that won’t elicit an immune response from the body, regardless of the source. These diets are nutritionally complete and safe to feed exclusively to your pet.

So, what is a concerned pet owner to do? Most veterinarians recommend choosing a food that contains high-quality ingredients, is made by a manufacturer with nutritional expertise and a track record of good quality control (few recalls) and has the appropriate nutritional profile for the individual pet. Click Here for more information about deciphering pet food labels and choosing a food. Until more research is available, it would be prudent to not choose diets containing exotic proteins such as alligator and kangaroo, whose benefits compared to chicken and beef have not been adequately evaluated. Avoid diets heavily based on legumes such as lentils and peas as well. Unless your pet has a proven adverse reaction to chicken, beef, or grains, it is not necessary and may even be harmful to feed foods that do not include these components. If you suspect your pet does have an allergy or other sensitivity to food, the best and safest course of action is to consult with your veterinarian about doing a food trial, where your pet is fed a hydrolyzed protein diet exclusively for a period of time and observe if the adverse reaction is alleviated. 

The veterinarians at Animal Hospital of North Asheville will be monitoring this situation as it evolves. As new information emerges regarding boutique, exotic and/or grain-free diets we will be sure to share it with our clients so that our pets can benefit from quality science-based nutritional information.


This is a helpful piece. I just recently spent almost 30 minutes at PetCo looking for a dogfood that was for "sensitive" and did not have legumes or potato in it as our Rotty had diarrhea that didn't clear with the vet's treatments. It was practically impossible to find as nearly all were grain free. I was stunned given the recent newsflash about the legumes and heart problems. We finally found one - Natural Balance-- lamb and rice (do I have to worry about arsenic now?) -- diarrhea is gone.