Grain in Pet Food and the Heart Disease Question

In the space of about a decade, pet food made without grain went from a niche product to one of the biggest categories in the pet aisle. The pitch was simple and appealing: dogs descend from wolves, wolves don't eat corn or wheat, and a more "ancestral" diet must be healthier. Then, in 2018, a cardiology question turned the trend into one of the most closely watched stories in veterinary nutrition. The evidence on both sides is more modest than the marketing or the headlines suggested.

The case that was made for dropping grain

The wolf argument is the weakest part. Dogs split from wolves thousands of years ago and changed in ways that matter for diet. A 2013 study published in Nature found that dogs carry extra copies of a gene for amylase, the enzyme that breaks down starch, which suggests they adapted to living alongside farming people. In practice dogs are omnivores, and they digest cooked grains such as rice and oats well.

Cats are a different case. They are obligate carnivores and need nutrients found in animal tissue, such as taurine. That doesn't make grain harmful to them, but it does mean the quality of the protein in a cat food matters far more than whether it contains rice.

A second assumption was that leaving out grain means fewer carbohydrates. It usually doesn't. Dry kibble needs starch to hold its shape, so grain is replaced with potatoes, sweet potatoes, tapioca, peas, lentils or chickpeas. Some of these recipes contain as much carbohydrate as the versions with grain, or more.

The third was allergy. True grain allergies are uncommon. When vets track down a food allergy, the cause is usually a protein. In dogs the most frequently reported culprits are beef, dairy, chicken and wheat. In cats they are beef, fish and chicken. Wheat appears on the dog list, but corn and rice rarely cause trouble.

2018: the FDA starts asking questions

In July 2018 the US Food and Drug Administration announced it was investigating reports of dilated cardiomyopathy, or DCM, in dogs. DCM is a disease of the heart muscle in which the heart enlarges and pumps weakly. It has a known genetic link in some large breeds, such as Dobermans and Great Danes, but the new reports involved breeds not normally prone to it, including golden retrievers, Labradors and mixed breeds.

The pattern that caught attention was diet. A large share of the reported dogs had been eating foods without grain, or foods with peas, lentils, other legumes or potatoes high on the ingredient list. Some of those dogs improved after their food was changed, which is unusual for DCM.

2019: brand names, and a backlash

In June 2019 the FDA published an update that named the brands most often mentioned in the reports. Sales of recipes without grain dipped, and manufacturers pushed back, arguing that the agency had linked their products to a disease without establishing cause. Veterinary cardiologists, meanwhile, continued to report cases and to study the dogs that recovered.

2022 and since: still unresolved

In December 2022 the FDA said it did not have enough data to establish a causal link between any particular diet and DCM, and that it would not issue further updates until there was meaningful new scientific information. Research has continued, looking at legumes, how ingredients and cooking affect taurine and other nutrients, and how individual foods are formulated. The fair summary today is that no one has proved that these diets cause heart disease, and no one has shown that leaving out grain offers health benefits for typical pets either.

Who might reasonably avoid grain

A dog or cat with a confirmed allergy to a specific grain can sensibly eat food without it. The only reliable way to confirm a food allergy is an elimination trial: feeding a diet with a single new or hydrolyzed protein for eight weeks or more under a vet's guidance, and then reintroducing ingredients one at a time. Some pets with particular digestive conditions also do better on recipes their vet recommends. In both cases, the reason is a diagnosis, not a label.

What to read on the bag instead

The most useful line on any pet food is the nutritional adequacy statement. Look for wording saying the food is "complete and balanced" for your pet's life stage according to AAFCO standards, ideally backed by feeding trials rather than formulation alone. The World Small Animal Veterinary Association also suggests asking whether the company employs a qualified nutritionist and runs its own quality control.

If your dog already eats a diet without grain and seems well, there is no need to panic. Raise it at the next checkup, especially for breeds at higher risk of heart disease, and ask whether a change makes sense. If you do switch, mix the new food in gradually over a week or so to avoid an upset stomach.