Grain-Free Diets and Heart Health

Few dog food topics cause as much worry as grain-free diets and heart disease. Owners ask us about it often. The honest answer is that scientists have learned a lot since 2018, but the full story is still not settled. Here is where things stand.

What is DCM?

Dilated cardiomyopathy (DCM) is a disease of the heart muscle. The heart enlarges and pumps weakly, which can lead to congestive heart failure or dangerous heart rhythms.

Some breeds are genetically prone to DCM, including Doberman Pinschers, Great Danes and other large breeds. What caught veterinarians’ attention around 2018 was DCM showing up in dogs and breeds that are not normally at risk, many of them eating similar kinds of food.

The FDA investigation

In July 2018 the U.S. Food and Drug Administration announced it was looking into reports of DCM in dogs eating certain diets, many labelled “grain-free”, that contained a lot of peas, lentils, other pulses and/or potatoes. In its 2019 update, the FDA said about 91% of the reported diets were grain-free and 93% contained peas and/or lentils.

In December 2022, the FDA posted what has so far been its last update. It said:

• It had received 1,382 reports of DCM in dogs between January 2014 and November 2022. These reports are voluntary and unverified.
• Report numbers alone “do not supply sufficient data to establish a causal relationship” with any product.
• It would not release further public updates “until there is meaningful new scientific information to share.”

The FDA has not asked for recalls and says it has no definitive information that these diets are unsafe. It also notes that reports involved both grain-free and grain-containing foods, and that most had peas, lentils or other pulses high on the ingredient list. Its advice is to work with your veterinarian before changing your dog’s diet.

Some people read the 2022 update as “case closed”. That is not what it said. The FDA stepped back from public updates, while research continued.

What research since then shows

More than 30 studies have now looked at the question. They do not all agree, and some are funded by pet food companies or pulse growers, so it helps to look at them together.

Evidence that diet matters:

• A 2022 study led by Tufts veterinary researchers followed dogs with DCM after a diet change. Dogs that had been eating “nontraditional” diets (mostly grain-free and high in pulses) showed small but measurable improvements in heart function after switching.
• A small 2023 trial in eight beagles (PLoS One, funded largely by Canadian pulse grower groups) found that a diet very high in wrinkled peas produced some DCM-like changes in heart measurements over 28 days. A lentil diet did not. The test diets were far higher in pulses than typical store-bought food.
• In a June 2026 review, Dr. Lisa Freeman of Tufts’ Cummings School of Veterinary Medicine wrote that diet-associated DCM “appears to be associated with diets high in pulses (peas, lentils, chickpeas, beans)”. She stressed that this includes grain-inclusive diets too, and that it “does not appear to be caused by a lack of grains”. Nor does it appear to be caused by a taurine deficiency, which was an early theory. The exact cause has not been identified, and researchers are looking at a possible problem with how the body handles certain fats.

Evidence that pulse-containing diets can be fine:

• A 2023 University of Guelph study fed 28 healthy Siberian huskies diets containing up to 45% whole pulses, with no grains, for 20 weeks. No heart problems were found. The study was funded by a pet food company.
• An 18-month study published in 2025 by researchers at another pet food company fed 60 healthy dogs grain-free and grain-inclusive diets with or without peas. All dogs were judged clinically normal for DCM at the end. One pea-containing group did show some changes in heart measurements, which the authors linked to more dogs in that group developing an unrelated valve condition.

How to read all this: healthy dogs on carefully made pulse-containing foods did fine in the company-funded trials, while veterinary cardiologists keep seeing affected dogs in the clinic, and the specific trigger is still unknown. Both things can be true. A disease that affects only some dogs, on some formulations, over long periods, is hard to reproduce in short trials.

What this means for your dog

Grain-free is not the issue on its own. The concern centres on diets with a lot of peas, lentils, chickpeas or beans, whether or not they contain grain. Check where pulses fall on the ingredient list. Several near the top, or split into forms like “pea protein”, “pea fibre” and “peas”, means they make up a large share.

Most dogs do not need a grain-free diet. If your dog is on a grain-free or pulse-heavy food for no particular medical reason, it is reasonable to ask your vet whether a different food makes sense.

Breed matters. If you have a Doberman, Great Dane or another breed with genetic DCM risk, talk to your vet about heart screening no matter what you feed.

Do not panic or switch abruptly. Change foods gradually, and get your vet’s input first. The FDA and Tufts both recommend involving your veterinarian, and a board-certified veterinary nutritionist if needed.

Signs to watch for

Tufts lists these possible signs of DCM:

• Coughing
• Difficulty breathing or fast breathing at rest
• Weakness or tiring easily
• Fainting or collapse

Some dogs show no signs at all, and some do not have a heart murmur. If you notice any of these, see your veterinarian promptly. If your dog is struggling to breathe or collapses, go to an emergency clinic right away.

The hopeful part: diet-associated DCM can slowly improve when the diet is changed, especially when it is caught early. It is still a potentially fatal disease, which is why early checks matter.

The short version

The link between some diets and DCM is real enough that veterinary cardiologists take it seriously, but it is not proven to be caused by any single ingredient, and “grain-free” is a poor shorthand for the concern. If your dog eats a pulse-heavy diet, belongs to an at-risk breed, or shows any of the signs above, book a conversation with your vet.

This guide is general information, not veterinary advice. Talk to your veterinarian about your own dog.