Grain-Free Dog Food and Heart Disease: What the Science Actually Says

For several years, dog owners have been hearing some pretty strong statements about grain-free food.

“Grain-free causes heart disease.”

“Never feed grain-free.”

“Dogs need grains.”

Sometimes those statements are delivered with such certainty that you would think the science had already settled the question.

It hasn't.

That does not mean the concerns surrounding diet and dilated cardiomyopathy, or DCM, should be dismissed. They shouldn't.

But it also doesn't mean we should stop asking questions when new evidence becomes available.

And some very interesting new evidence just arrived.

On September 16, 2026, researchers published a large study using data from the Dog Aging Project examining grain-free feeding and new cardiac diagnoses in dogs.

The study included data from 47,444 dogs.

Its conclusion deserves our attention.

So do its limitations.

Because if we are going to say that we follow the science, we have to be willing to follow all of it.

The September 2026 Study

The study was published in Veterinary Medicine and Science:

“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.”

Read the full September 16, 2026 study here

Researchers examined whether grain-free diet status was associated with new owner-reported cardiac diagnoses.

After adjusting for potential confounding variables, the odds ratio for a new cardiac diagnosis associated with grain-free feeding was 1.05, with a 95% confidence interval of 0.91 to 1.21 and a p-value of 0.52.

In practical terms, the researchers did not find a statistically significant association between grain-free diet status and new cardiac diagnoses overall.

Their conclusion was that the potential effect of grain-free feeding on new diagnoses of cardiac disease as a whole within this dataset was likely minimal or absent.

That is important.

But before anybody turns that sentence into a victory lap for grain-free food, keep reading.

This Study Does Not Prove Every Grain-Free Food Is Safe

This is where I believe nutrition discussions often go wrong.

We find a study supporting what we already believe, grab the headline, and stop reading.

I won't do that.

This study does not prove that every grain-free food is safe.

It does not prove that diet-associated DCM doesn't exist.

It does not prove that peas, lentils, potatoes, or other ingredients can never be involved in diet-related cardiac problems.

It does not tell us that every formulation carrying the words “grain-free” should be considered nutritionally equivalent.

And importantly, this study was not designed to answer the narrow question of whether grain-free diets cause or do not cause DCM specifically.

The cardiac diagnoses included murmurs, congestive heart failure, valve disease, arrhythmias, cardiomyopathy, hypertension, and other conditions.

Only 54 dogs in the relevant dataset were reported with cardiomyopathy.

The researchers themselves state that their study likely was not sensitive enough to determine the effect of grain-free feeding on the incidence of individual cardiac diseases.

That distinction is critical.

The study is reassuring.

It is not the final word.

Those are two very different statements.

There Was Another Interesting Finding

The researchers also discovered something that should make all of us think a little harder about nutrition surveys.

A lot of owners didn't actually know whether their dogs were eating grain-free food.

Among more than 13,000 dogs for whom researchers could compare owner reports with actual ingredient information, owners who said their dogs ate grain-free food were correct only about 49 percent of the time.

Think about that for a moment.

Something as seemingly simple as asking, “Does your dog's food contain grain?” produced substantial misclassification.

The researchers specifically analyzed whether that error could have distorted their results. Their simulations suggested that this type of misclassification would tend to weaken a real association rather than manufacture a false one.

To me, there is a larger lesson here.

The front of the bag is not the formulation.

And sometimes even the person feeding the food doesn't know exactly what is in it.

Turn the package over.

How Did We Get Here?

In 2018, the FDA announced that it was investigating reports of DCM in dogs eating certain diets.

Many of the reported foods were labeled grain-free and contained high proportions of peas, lentils, other pulses, or potatoes.

The reports deserved investigation.

Some involved breeds that were not traditionally considered genetically predisposed to DCM.

That was worth paying attention to then, and it remains worth studying today.

But there is an important distinction between identifying a signal and establishing causation.

The FDA has explicitly stated that adverse-event reports can signal a potential problem, but those reports by themselves do not provide sufficient evidence to establish a causal relationship between a product and DCM.

There is another fact that sometimes disappears from this discussion:

DCM reports also included dogs eating grain-containing diets.

That doesn't prove grain-inclusive food causes DCM.

Of course it doesn't.

But that is exactly the point.

The presence or absence of grain alone may not tell us nearly as much as people have been led to believe.

What About the Studies That Found a Diet Connection?

We shouldn't ignore those either.

A prospective 2022 study followed dogs with DCM or subclinical cardiac abnormalities that had been eating what researchers classified as nontraditional diets.

After diet changes, and with taurine supplementation in many of the dogs, researchers found small but statistically significant improvements in some echocardiographic measurements.

That matters.

It is evidence that deserves to be considered.

It is also worth understanding exactly what was studied.

“Nontraditional” is not synonymous with “grain-free,” and multiple interventions occurred in some of these dogs. These studies help build the evidence base, but they do not establish that removing grain itself is the mechanism responsible for DCM.

That question remains much more complicated.

For transparency, that 2022 study reported funding from Nestlé Purina PetCare and the Barkley Fund.

And since I believe transparency should apply equally, the new 2026 Dog Aging Project paper also contains disclosures. One author reported grants and lecture honoraria from the Morris Animal Foundation and Purina Institute, while another reported grants from several veterinary foundations. The remaining authors declared no conflicts of interest.

A disclosure does not automatically invalidate research.

It is information.

Read the methods. Read the results. Read the limitations. Read the funding and conflicts disclosures.

Then evaluate the evidence.

That's how this should work.

Grain-Free Is a Category, Not a Formulation

This may be the biggest problem I have with the entire grain-free debate.

We keep talking about “grain-free food” as though it were one food.

It isn't.

Take two bags off a shelf.

Both can say grain-free across the front and contain completely different protein sources, different amounts and types of legumes, different fibers, different amino acid profiles, different fat levels, different mineral concentrations, and completely different formulations.

The only thing we know from the words “grain-free” is what isn't supposed to be there.

That tells us remarkably little about what is there.

The same reasoning applies in the other direction.

Putting rice, oats, barley, or another grain into a food doesn't automatically make the formulation superior.

There are well-formulated grain-inclusive foods.

There are poorly formulated grain-inclusive foods.

There are well-formulated grain-free foods.

And there can be poorly formulated grain-free foods.

Formulation matters more than the marketing category on the front of the bag.

The Whole Dog Matters Too

Nutrition doesn't happen in a vacuum.

Neither does heart disease.

Genetics matter.

Certain breeds have recognized hereditary or familial predispositions to DCM. That has been known long before the current grain-free discussion began.

Age matters.

Underlying health conditions matter.

Body condition matters to overall health.

Appropriate physical activity matters to overall health.

And nutrition certainly matters.

But acknowledging that diet matters is very different from pretending that one characteristic of a diet explains every case of a complicated disease.

Interestingly, the September study adjusted its primary analysis for several potential confounding variables, including breed status, sex, neuter status, size, and survey year as a proxy for age.

Some of those variables were associated with new cardiac diagnoses.

Grain-free diet status was not.

Again, that doesn't close the case on diet-associated DCM.

It simply tells us that biology is more complicated than a slogan.

Here's Where I Stand

I think transparency matters, so I'll give you mine.

I sell both grain-inclusive and grain-free foods.

I feed my own dogs grain-free food.

I have fed grain-free foods for many years, and based on the evidence available to me today and the formulations I choose, I am comfortable continuing to do so.

But please understand something important:

My dogs are not a scientific study.

My personal experience does not prove grain-free food is safe for every dog.

And my personal preference doesn't mean grain-inclusive food is bad.

I would never tell somebody that simply because I choose one approach, every dog should eat the same way.

Different dogs have different needs.

My job as a nutrition professional isn't to defend a team.

It is to keep learning.

I Don't Need Grain-Free to “Win”

This is probably the most important thing I can tell you about my position.

I don't need grain-free food to win this argument.

I don't need grain-inclusive food to lose.

There shouldn't even be teams.

If credible evidence eventually demonstrates that something I believe today is wrong, I want to see that evidence.

If the evidence is strong enough, I will change my mind.

That isn't weakness.

That's science.

Science isn't supposed to protect our beliefs.

It's supposed to test them.

Be Careful With Certainty

Whenever someone speaks with absolute certainty about an unsettled scientific question, I become interested in the evidence behind that certainty.

Not the title.

Not the profession.

Not the logo on the building.

Not the logo on the bag.

The evidence.

If someone tells you grain-free food causes DCM, ask to see the research.

If someone tells you grain-free food could never contribute to DCM, ask them for the research too.

If somebody says “studies show,” ask which studies.

Then read them.

• How many dogs were studied?
• What diets were actually fed?
• How was dietary exposure determined?
• Were individual ingredients evaluated?
• Was the outcome specifically DCM, or were multiple heart conditions grouped together?
• Was it observational research or a controlled feeding trial?
• Were other variables considered?
• Who funded the research?
• What conflicts were disclosed?
• What did the researchers themselves say their study could not prove?

That last question can save you from a lot of bad science communication.

Don't Borrow Someone Else's Certainty

Dog owners are surrounded by opinions.

Food companies have opinions.

Retailers have opinions.

Veterinarians have opinions.

Nutritionists have opinions.

Social media certainly has opinions.

Credentials matter. Expertise matters. Clinical experience matters.

But none of those things should make a scientific question off-limits to examination.

You should be able to ask:

What is the evidence?

And you should be able to ask that question without being made to feel foolish for asking it.

I want people who walk through my door to think.

I don't want them simply replacing somebody else's opinion with mine.

Read.

Question.

Learn.

Then make the best decision you can for the animal standing in front of you.

So What Does the September 2026 Study Actually Change?

It adds an important piece of evidence.

In a dataset involving 47,444 dogs, researchers using multiple statistical approaches did not find a significant association between grain-free diet status and new owner-reported cardiac diagnoses overall.

That deserves to be discussed.

It does not prove every grain-free formulation is safe.

It does not disprove diet-associated DCM.

It does not tell us that ingredients don't matter.

It does not erase earlier research.

And it does not give anyone permission to stop investigating.

In fact, the authors point toward the possibility that the safety question may ultimately be formulation-specific rather than determined simply by whether a food contains grain.

Now that is an interesting question.

Maybe we have spent too much time asking:

“Is it grain-free?”

And not enough time asking:

“How is it formulated?”

Follow the Evidence Wherever It Goes

I don't know what the next major DCM study will find.

Nobody does.

Maybe future research will identify specific ingredients, inclusion levels, nutrient interactions, processing effects, genetic susceptibilities, or combinations of factors that explain some of the cases we've seen.

Maybe some of our current assumptions will hold up.

Maybe some won't.

That's why we keep studying it.

For now, I am going to continue doing exactly what I believe anyone discussing animal nutrition should do.

Read the research.

Read beyond the abstract.

Understand the limitations.

Look for conflicts.

Question absolutes.

Be willing to change.

And never become so attached to a position that new evidence becomes an inconvenience.

I sell grain-free food.

I sell grain-inclusive food.

I feed my own dogs grain-free.

None of those facts determines what the science says.

The evidence does.

And right now, the evidence tells me that the relationship between diet and canine heart disease is considerably more complicated than four words:

“Grain-free causes heart disease.”

Our dogs deserve a better conversation than that.

They deserve one built on evidence, curiosity, humility, and the willingness to keep learning.

Sources and Further Reading

O'Brien J, Bishop M, Dog Aging Project Consortium, Tolbert MK, Ruple A. (2026).
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. Published September 16, 2026.

Read the September 16, 2026 Dog Aging Project study

Freeman LM, Rush JE, Adin DB, et al. (2022).
Prospective study of dilated cardiomyopathy in dogs eating nontraditional or traditional diets and in dogs with subclinical cardiac abnormalities.
Journal of Veterinary Internal Medicine. 36(2):451-463.

Read the 2022 prospective DCM study

U.S. Food and Drug Administration.
FDA Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy.

Read the FDA investigation into diet and canine DCM