Peas, lentils, and the heart disease that follows
Doges Editorial · 2026-06-26 · 6 min read
For the past eight years, veterinary cardiologists have been tracking a form of heart disease tied not to genetics but to what dogs eat. A June 2026 update from Tufts University adds a new piece to the puzzle — and reminds owners that grain-free is no longer the whole story.
The cough starts quietly. It might sound like a hairball, or a minor respiratory thing, or nothing in particular. Weakness on walks. A reluctance to do the stairs. Fainting, sometimes, or an episode that looked almost like fainting. Or — and this is the harder version — no symptoms at all, just a routine vet visit that catches something wrong with the heart.
This is dilated cardiomyopathy: the second most common heart disease in dogs, a condition in which the heart muscle weakens and enlarges until it can no longer pump efficiently. In some dogs, it's genetic — Doberman Pinschers and Great Danes carry particular susceptibility, and for those dogs, the disease tends to run in families, worsen over time, and resist treatment. But in 2018, veterinary cardiologists began noticing something else: dogs without the genetic predisposition were developing DCM too. And the cases clustered around a specific type of diet.
The 2018 alert, and what happened next
In July 2018, the FDA issued an alert about a possible link between grain-free dog foods and an unusual rise in DCM cases. Grain-free diets had become enormously popular — marketed as more natural, more ancestral, better for digestion. The alert set off years of investigation, debate, and research. For a while, the leading hypothesis was taurine: dogs eating grain-free food might be deficient in this amino acid, and the deficiency might be harming their hearts.
That hypothesis has largely been set aside. According to Dr. Lisa M. Freeman, DVM, PhD, a board-certified veterinary nutritionist at Tufts University's Cummings School of Veterinary Medicine, the research now points somewhere else — and somewhere more specific.
The ingredient at the center
The thread connecting the affected dogs is not the absence of grains. It is the presence of pulses: peas, lentils, chickpeas, and dry beans. These ingredients have become common thickeners and protein sources across the pet food industry — in grain-free foods, but also in grain-inclusive foods that happen to be high in legumes. A bag that includes whole grains but is loaded with pea protein is just as much a concern as one that markets itself as grain-free.
This distinction matters. Many dog owners switched away from grain-free foods after the 2018 alert and assumed they had solved the problem. The Tufts team's ongoing research suggests the ingredient to watch is in the label, not in the marketing category.
What the Tufts team just found
In research published in January 2025 in the American Journal of Veterinary Research, Freeman's team studied 53 dogs — 25 with DCM eating high-pulse diets, plus 4 with DCM on low-pulse diets and 24 healthy controls — and identified a potential cellular mechanism for the disease: elevated levels of a urine biomarker consistent with phospholipidosis, a condition in which a specific class of fat accumulates abnormally inside cells and can disrupt organ function. The biomarker concentration correlated with diet pulse score at r = 0.52 across the sample. In December 2025, the study earned Freeman the AKC Canine Health Foundation's inaugural Canine Health Discovery of the Year Award. It is the first specific biological pathway identified in the eight-year investigation.
Our team identified a potential mechanism for diet-associated DCM — higher levels of a urine biomarker in dogs with diet-associated DCM suggesting phospholipidosis, an abnormal metabolism of a type of fat. This is just one of more than 30 scientific studies that have been published on diet-associated DCM, adding important pieces to the puzzle for the cause of negative effects of high-pulse diets on dogs' hearts.
— Dr. Lisa M. Freeman, DVM, PhD, DACVIM, Tufts Cummings School of Veterinary Medicine
More than 30 studies over eight years represents genuine scientific momentum. The picture is still incomplete — not every dog on a pulse-heavy diet develops DCM, and the specific trigger has not been confirmed. But the direction the research points is consistent, and the biological clue is now measurable.
What to watch for
The disease is particularly difficult to catch because it can be silent. Freeman's guidance to owners is direct on this point:
Possible symptoms of diet-associated DCM include coughing, difficulty breathing, weakness, and fainting, although dogs can also be symptom-free and may not have heart murmurs.
— Dr. Lisa M. Freeman, DVM, PhD, DACVIM, Tufts Cummings School of Veterinary Medicine
The risk can show up before symptoms do. In a 2024 analysis of 67 dogs, those eating legume-rich diets had premature ventricular contractions — irregular electrical misfires in the heart muscle — at a rate of 17 percent, compared to just 2 percent in the low-legume group. Those are the kinds of changes an electrocardiogram catches while a dog still runs happily around the yard.
"Symptom-free" is the hardest part. A dog who is quietly tiring faster on walks, who is a little less willing to keep pace, who seems slightly less interested in the full morning loop — these can be early signs of cardiac changes that a stethoscope and an echocardiogram would catch. They can also be nothing. The distinction is hard to make at home, which is part of why routine vet visits matter for dogs on high-pulse diets.
The good news in the research
Research has shown diet-associated DCM can slowly improve if diet is changed (especially if caught early). Nonetheless, it remains a potentially deadly disease.
— Dr. Lisa M. Freeman, DVM, PhD, DACVIM, Tufts Cummings School of Veterinary Medicine
This is the meaningful news embedded in the Tufts update: unlike genetic DCM, which tends to worsen regardless of intervention, the diet-associated form can reverse with a food change — provided it's caught before the damage is too advanced. The heart muscle, when the offending ingredient is removed, has shown capacity to recover. The key is finding out before the disease progresses.
What to look at on the label
The practical question for any dog owner is this: does the current food list peas, lentils, chickpeas, or dry beans among its first several ingredients? Ingredient lists are ordered by weight before cooking, so an ingredient in the first five or six positions is present in significant quantity. A bag where "pea protein" or "lentils" appear in the first third of the ingredient list may be worth discussing with a veterinarian — regardless of what the front of the bag says about grains.
This is not a call to panic about every bowl of kibble. Most dogs on pulse-containing diets are fine, and researchers are still working out why some dogs appear more susceptible than others. What it is, instead, is the kind of information that is easy to act on: read the label, ask your vet at the next visit, pay attention to any subtle changes in what your dog is willing to do on a walk. The thing to watch is not what the marketing says. It is what is actually in the bag.