For the past several years, dog owners have been warned about a possible connection between grain-free dog food and dilated cardiomyopathy (DCM), a potentially serious disease in which the heart becomes enlarged and weakened.

The concern began receiving widespread attention in 2018, when the U.S. Food and Drug Administration (FDA) announced that it was investigating reports of DCM in dogs eating certain diets—many of which were marketed as grain-free and contained substantial amounts of peas, lentils, other legumes, or potatoes. In the FDA’s early case data, more than 90% of reported foods were labeled grain-free, while 93% contained peas and/or lentils.

That association led many veterinarians and dog owners to a simple conclusion:

Grain-free food causes DCM.

But nutritional science rarely turns out to be that simple.

A major new study published September 16, 2026, using data from the Dog Aging Project, adds an important piece to the puzzle. Researchers followed tens of thousands of dogs and found that feeding a grain-free diet was not associated with an increased likelihood of developing a new cardiac diagnosis during the study period.

The finding does not mean every grain-free food is automatically safe. Instead, it supports an increasingly important distinction:

The absence of grains may not be the problem. The formulation replacing those grains may matter far more.

The New Dog Aging Project Study

The 2026 study, led by researchers from Virginia Tech and Texas A&M University, analyzed data from the Dog Aging Project, one of the largest ongoing studies of canine health and longevity.

A total of 47,444 dogs were included in the analysis. More than 26,000 completed at least one annual follow-up survey, and end-of-life surveys were available for 7,786 dogs. Researchers examined whether dogs reported as eating grain-free diets were more likely to develop new cardiac conditions.

After adjusting for factors such as breed status, sex, neuter status, body size, and year of participation, researchers calculated an odds ratio of 1.05 for new cardiac diagnoses among grain-free-fed dogs, with a 95% confidence interval of 0.91–1.21 and a p-value of 0.52.

In plain English, the researchers found no statistically significant increase in cardiac diagnoses associated with grain-free feeding.

Their unadjusted analysis reached essentially the same conclusion, producing an odds ratio of 0.98. Multiple statistical modeling approaches yielded similar results.

For dog owners who have been told that simply removing grain from a dog’s diet creates a heart-disease risk, this is an important finding.

Something Else the Researchers Discovered: Owners Often Don’t Know Whether Their Food Is Grain-Free

One of the most fascinating findings had nothing directly to do with heart disease.

Researchers compared what owners thought they were feeding with the actual ingredient lists of those foods.

Among 13,049 diets that could be evaluated, owners correctly identified foods they believed to be grain-free only 49% of the time. By comparison, owners who said their dog’s food contained grain were correct approximately 92% of the time. Overall classification accuracy was 77%.

In other words, among owners who reported feeding grain-free food, more than half were wrong about the grain status of the diet.

That finding demonstrates one of the major problems researchers face when studying nutrition: front-of-bag terminology does not necessarily tell us very much about what a dog is actually eating.

And it raises an even larger issue with the entire DCM debate.

“Grain-free” describes what isn’t in a food. It tells us almost nothing about what replaced it.

Grain-Free Is Not an Ingredient

Removing rice, corn, wheat, barley, or another grain does not automatically make a food nutritionally superior—or nutritionally dangerous.

The more relevant question may be:

What ingredients replaced those grains, and in what quantities?

That distinction has been present in the FDA data from the beginning. Although more than 90% of the diets reported in the FDA’s early DCM cases were grain-free, 93% contained peas and/or lentils. Potatoes were also present in some diets. The FDA’s nutrient testing did not identify obvious differences in average protein, fat, taurine, cystine, or methionine concentrations between the grain-free and grain-containing products it tested.

This has led researchers to investigate whether particular ingredients, combinations of ingredients, fiber characteristics, amino-acid availability, bile-acid metabolism, or other aspects of formulation could influence cardiac health.

A 2023 controlled feeding study illustrates why this distinction matters. Researchers fed Beagles diets based on rice, lentils, or wrinkled peas. After 28 days, dogs receiving the high-pea diet developed several subclinical cardiac changes, including increased left ventricular systolic diameter, reduced stroke volume, and increased NT-proBNP. Yet the lentil-based grain-free diet did not produce the same DCM-associated changes, and plasma taurine remained unchanged.

That study did not demonstrate clinical DCM, and some of the experimental diets had nutritional limitations that prevent extrapolating the findings directly to commercial foods. But it reinforced an important point:

Two foods can both be called “grain-free” while having very different physiological effects.

What About the Studies That Found Improvement After Changing Diets?

There is legitimate research on the other side of the discussion as well.

In a 2022 prospective study of dogs with DCM, researchers evaluated dogs eating what they termed “nontraditional” versus traditional diets. Dogs previously consuming nontraditional diets showed modest but statistically significant improvements in certain cardiac measurements after their diets were changed. Interestingly, none of the dogs in the study had low plasma or whole-blood taurine concentrations when they entered the study.

Another small 2022 study followed 20 dogs with subclinical cardiac abnormalities. Ten dogs had been eating grain-free diets and ten grain-inclusive diets. After dietary changes, the grain-free group showed greater improvements in certain cardiac measurements and biomarkers.

Those findings cannot simply be dismissed.

But they also do not establish that the absence of grain itself caused the abnormalities. A grain-free kibble containing large quantities of pea protein, pea starch, lentils, chickpeas, or potatoes is nutritionally very different from a grain-free food made predominantly from meat, organs, fish, and eggs.

That distinction is precisely what the new Dog Aging Project study could not investigate. The authors specifically identified this as an important limitation: their longitudinal dataset did not contain sufficiently detailed ingredient information to determine whether individual ingredients within grain-free foods might influence cardiac health.

DCM Is Also a Multifactorial Disease

Another reason the debate is difficult is that DCM is not one single nutritional disease.

Some breeds—including Doberman Pinschers and other large or giant breeds—have well-recognized genetic predispositions to DCM. Taurine deficiency can contribute to DCM in certain dogs, with Golden Retrievers receiving particular attention in the scientific literature. Other cases can involve nutritional factors that remain poorly understood.

The 2026 Dog Aging Project study also found that variables such as breed status, body size, neuter status, and study year were more strongly associated with reported cardiac diagnoses than grain-free status itself. The authors emphasized that these potential confounding variables deserve careful consideration in future nutrition studies.

This matters because association is not necessarily causation.

If a particular population of owners disproportionately feeds certain diets to particular breeds, ages, or types of dogs, simply comparing “grain-free” and “grain-containing” groups can produce misleading results unless those differences are accounted for.

What This Means for Lincoln Naturals

Lincoln Naturals is grain-free, but that description tells only a small part of the story.

Unlike many conventional grain-free kibbles, Lincoln Naturals does not remove grains and replace them with large quantities of peas, lentils, chickpeas, legumes, potatoes, or other starches.

Our recipes are built primarily around animal-derived foods.

The USDA Chicken recipe contains chicken, chicken liver, salmon, and egg followed by modest quantities of broccoli, carrots, berries, mushrooms, herbs, and spices. It contains a maximum of approximately 3.2% carbohydrate. The USDA Beef recipe similarly centers on beef, beef liver, salmon, and egg and contains a maximum of approximately 2% carbohydrate.

Lincoln Naturals contains 96% animal-derived ingredients, with no corn, rice, starches, soy, or potatoes.

That makes Lincoln Naturals fundamentally different from the category of extruded grain-free foods in which grains are removed primarily so that large quantities of concentrated pulse or potato ingredients can take their place.

What Should Dog Owners Look For?

Rather than choosing or rejecting food based upon one marketing term, dog owners should consider the entire ingredient and nutrient profile.

1. Look beyond the words “grain-free.” Determine what replaced the grain. A meat-dominant food and a pea-starch-dominant food should not be treated as nutritionally equivalent simply because both lack wheat or rice.
2. Pay attention to heavy pulse inclusion. Peas, lentils, chickpeas, beans, and related ingredients remain an active area of DCM research, particularly when they appear prominently or repeatedly in a formulation.
3. Prioritize high-quality animal protein. Animal-derived ingredients supply highly bioavailable amino acids and other nutrients important to normal cardiac and metabolic function.
4. Choose nutritionally complete foods. Whether a diet contains grain is less meaningful than whether the complete formulation supplies the nutrients a dog requires in appropriate amounts and forms.
5. Talk with your veterinarian when individual risk is high. Dogs from breeds predisposed to DCM, dogs with murmurs or arrhythmias, or dogs showing exercise intolerance, weakness, coughing, rapid breathing, or fainting may warrant a veterinary examination and, when appropriate, cardiac testing.

The Bigger Lesson From the DCM Debate

Nutrition science advances by becoming more specific, not less.

The original FDA investigation identified a genuine signal that deserved scientific attention. Certain diets appeared disproportionately in reports involving DCM, and researchers were right to investigate them.

But “grain-free” may ultimately prove to have been too broad a category.

The newest Dog Aging Project research involving more than 47,000 dogs found no statistically significant association between grain-free feeding and new cardiac diagnoses overall. At the same time, other research suggests that particular formulations—especially those relying heavily on certain pulses such as peas—deserve continued investigation.

The emerging message is therefore considerably more nuanced than the headlines of several years ago:

Grain-free is not a nutritional formulation. It is a label.

What matters is what is actually inside the food.

At Lincoln Naturals, our goal has never been simply to remove grain. We formulate our freeze-dried recipes around real muscle meat, organ meat, salmon, eggs, and small amounts of whole fruits and vegetables, without relying on grains, legumes, potatoes, or concentrated starches to build the food.

As canine nutrition research continues to evolve, that ingredient-level distinction matters more than ever.

Works Cited

O’Brien, Janice, et al. “Multiple Modelling Methods Suggest That Grain-Free Diets Are Not Predictive of New Owner-Reported Cardiac Diagnoses Over Two Years in the Dog Aging Project, Despite Owner Misclassification of Diet.” Veterinary Medicine and Science, vol. 12, no. 5, 2026, e71213. doi:10.1002/vms3.71213.

U.S. Food and Drug Administration. “FDA Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy.” Center for Veterinary Medicine, updated December 23, 2022.

Freeman, Lisa M., et al. “Prospective Study of Dilated Cardiomyopathy in Dogs Eating Nontraditional or Traditional Diets and in Dogs With Subclinical Cardiac Abnormalities.” Journal of Veterinary Internal Medicine, vol. 36, no. 2, 2022, pp. 451–463.

Haimovitz, Dana, et al. “Effect of Diet Change in Healthy Dogs With Subclinical Cardiac Biomarker or Echocardiographic Abnormalities.” Journal of Veterinary Internal Medicine, vol. 36, no. 3, 2022, pp. 1057–1065.

Quilliam, Chloe, et al. “Effects of a 28-Day Feeding Trial of Grain-Containing Versus Pulse-Based Diets on Cardiac Function, Taurine Levels and Digestibility in Domestic Dogs.” PLOS ONE, vol. 18, no. 5, 2023, e0285381.

Morris, Elizabeth M., et al. “Different Carbohydrate Sources in Dog Foods Supported Overall Health and Cardiac Function: An 18-Mo Prospective Study in Healthy Adult Dogs.” Journal of Animal Science, vol. 103, 2025, skaf225.

Mornard, Léa, Anna Carolina Massara Brasileiro, and Mário Marcondes-Santos. “Role of Diet as a Predisposing Factor for Dilated Cardiomyopathy in Dogs: A Narrative Review.” Veterinary Sciences, vol. 12, no. 11, 2025, p. 1106.