Evidence review

The Pulse Question

Name: Hearth & Hounds
Rating: 5

Grain-free diets and canine dilated cardiomyopathy: what the FDA investigation was, what eight years of research established, who funded each study, and what remains unresolved.

2026-08-26 · 13 sources · Hearth & Hounds HTX

Last reviewed 2026-08-26 · By Kourtenay Dolmos · Founder, Hearth & Hounds · LIMA-Informed · Houston, TX

I came to nutrition before I came to training. That was 2018, which happens to be the same year the FDA opened the investigation everybody still quotes at me, and it is why I have been reading this particular argument for as long as it has existed.

I wrote this because clients keep arriving frightened, holding advice they were given in good faith, and I could not point them at anything that laid out the whole picture instead of half of it. Every source is here, and so is the name of whoever funded it.

I am not a veterinarian and this is not medical advice. What I can do is show you the evidence as it actually stands, so the conversation you have with your vet is a better one.

Settled

Grains were never the issue

Both sides now agree, including the researcher whose work raised the alarm. A grain-inclusive food built on peas draws the same suspicion as a grain-free one. The word on the bag was never the thing to watch.

Settled

The taurine theory was wrong

It was the entire explanation in 2018. The prospective study that followed it up found no taurine deficiency in any enrolled dog, and those dogs still improved when the food changed.

Real, and rare

Something happens to a few dogs eating a lot of peas and lentils

Individual dogs got sick, changed food, and measurably recovered. That is difficult to explain away. What nobody can explain is why it reaches those dogs and not the millions of others.

Never shown

It was never demonstrated as a widespread danger

Grain-free sales grew five-fold. At the hospitals that diagnose heart disease, the rate of diagnosis did not move.

The FDA file, and why it proves nothing

A complaint box. Anyone could file a report, three quarters of the dogs were breeds that get heart disease anyway, and the reports arrived whenever the press covered it.

The file holds voluntary adverse event reports submitted through the FDA’s public reporting portal. It has no control group, no randomization, no verification requirement and no denominator. It was not built to establish causation, and the agency never claimed it had.

The FDA closed public updates on 23 December 2022. The total stood at 1,382 dogs across roughly nine years, and only 255 of those arrived after July 2020.

"While adverse event numbers can be a potential signal of an issue with an FDA regulated product, by themselves, they do not supply sufficient data to establish a causal relationship with reported product(s)."

FDA Center for Veterinary Medicine, final update, December 2022

Four properties that limit what the file can show4 points

01
Three quarters were breeds already predisposed
Of 305 reports with a breed recorded, 223 were Goldens, Great Danes, Dobermans, Boxers, Cockers or Bulldogs. A sample weighted toward predisposed breeds cannot isolate a dietary effect from a genetic one.
02
The FDA acknowledged breed reporting bias
Golden Retriever social media communities were urging owners and veterinarians to file, which concentrated submissions in a single breed.
03
The report curve follows the press
Reports climbed after the July 2018 announcement and again after the June 2019 brand list, then fell away. Pharmacovigilance has a name for the pattern: the Weber effect.
04
The undercount correlates with the exposure
The FDA states cases go unreported because diagnostic testing and treatment can be complex and costly to owners. Those owners are also the ones not buying premium food, so the gap in the data lines up with the diet under investigation.

The June 2019 brand list ranked sixteen brands by raw report count with no correction for units sold. Uncorrected for market share, such a count ranks sales volume.

Timeline, 2018 to 20267 entries

01
July 2018: FDA opens the investigation
Announces it is examining DCM reports in dogs eating diets high in peas, lentils, other legume seeds and potatoes. Reporting volume climbs immediately.
02
December 2018: Kaplan publishes the first substantial case series
Twenty-four taurine-deficient Golden Retrievers, 23 of them eating grain-free or legume-rich food. Twenty-three improved after a diet change plus taurine.
03
June 2019: the brand list is published
Sixteen brands named by raw report count. Consumer coverage peaks here, and so does the reporting curve.
04
2020 to 2022: the taurine hypothesis fails
Prospective work finds DCM in dogs eating suspect diets whose taurine is entirely normal. Their hearts still improve on a diet change.
05
December 2022: FDA ends public updates
No causal relationship established, and nothing further promised until meaningful new science exists. Four and a half years after the announcement that moved the market.
06
October 2024: a mechanism candidate is identified
Fifty-three dogs. Urinary di-22:6-BMP, a phospholipidosis biomarker, runs higher in dogs eating high-pulse diets and rises with the pulse load of the food.
07
June 2026: the position consolidates around pulses
More than thirty published studies. Grains excluded, taurine excluded, pulses implicated, mechanism still unidentified.

Who funded each study

Seven of the eight significant studies were paid for by a dog food company or a consultancy serving them. The exception is the one that started the concern.

Industry funding is the norm in veterinary nutrition, because feeding trials have no other funding source, and a well-designed study stays well-designed whoever paid for it. The practical consequence is narrow: "a study found" carries no weight here on its own, in either direction.

The funding ledger8 studies

Study	Funding and affiliations	Finding	Direction
Prospective DCM study, nontraditional vs traditional dietsFreeman, JVIM 2022, n=76	Nestlé Purina PetCareAnd the Barkley Fund. Authors disclose Purina, Hill’s and Royal Canin relationships.	Systolic function improved over nine months after a change off pulse-rich food. No dog was taurine deficient.	Diet effect
Labrador 30-day legume feeding trialWaltham, BMC Vet Res 2022, n=11	Mars PetcareAll authors were Mars employees at the time of the work.	At 60% legume inclusion, red cells fell 7.7%, phosphate rose 41.8%, urinary taurine fell 77% within thirty days.	Diet effect
Taurine deficiency and DCM in Golden RetrieversKaplan, PLoS ONE 2018, n=24	No specific fundingThe authors state they received no specific funding for this work. One disclosure: an author directs the fee-for-service amino acid laboratory at UC Davis. The only study here with no commercial sponsor.	23 of 24 dogs improved after a diet change plus taurine. Nine of eleven in heart failure resolved their congestion.	Diet effect
DCM incidence vs grain-free sales, 2000 to 2019Frontiers Anim Sci 2022, n=68,297	BSM Partners LLCFour authors employed there. BSM consults for grain-free and grain-inclusive manufacturers alike.	Sales rose from $900M to $5.4B. DCM diagnosis rate across 14 referral centers showed no trend (P=0.98).	No effect
18-month carbohydrate source trialJ Anim Sci 2025, n=60	Hill’s Pet NutritionAll authors current or former Hill’s employees.	Four balanced diets including grain-free with 16.4% peas. No cardiac biomarker change, no DCM, taurine unaffected.	No effect
Whole pulse inclusion up to 45%Singh, J Nutr 2023, n=28	University of Guelph, with Champion Petfoods co-authorsThree authors employed by Champion Petfoods, which makes Orijen and Acana, two of the sixteen brands on the FDA list. One author from Protein Industries Canada.	Pulses at 0, 15, 30 and 45% over 20 weeks produced no difference in echocardiography, NT-proBNP or troponin I.	No effect
Review of canine DCM in the wake of diet-associated concernsMcCauley, J Anim Sci 2020	BSM Partners LLCConflict disclosure was absent on publication and added by corrigendum after readers questioned it.	Concluded the evidence did not establish a link and the mechanism remained unknown. Widely cited by grain-free brands.	No effect
Urinary phospholipidosis biomarkerFreeman, AJVR 2024, n=53	Tufts groupSame lead author as the 2022 Purina-funded study and the 2026 position update. Received the AKC Canine Health Foundation’s first Health Discovery Award.	Dogs eating high-pulse diets had elevated urinary di-22:6-BMP, rising with the pulse load of the food (r=0.52).	Diet effect

Reading the table

Funding does not divide along the conclusion

The available account is that grain-inclusive manufacturers funded a scare to damage a competing category. The ledger does not support it. Hill’s, a large grain-inclusive manufacturer, funded a study finding no cardiac effect. Purina and Mars funded work supporting a diet effect. BSM Partners, which found no link twice, consults for manufacturers on both sides.

The sharpest conflict runs the other way. The study reporting that 45% pulse inclusion has no cardiac effect carries three co-authors employed by the manufacturer of two brands named on the FDA list.

Each funder’s interest sits in the framing rather than the result. The Hill’s finding supports a position that formulation expertise determines the outcome, which serves Hill’s whichever way the cardiac data falls.

One further concentration is worth seeing. Three of the four entries pointing to a diet effect share a lead author, and the 2026 statement of the mainstream position is hers as well. That is a small evidence base resting on one laboratory.

The case on each side

A measurable effect appears in a small number of dogs eating high pulse loads, and no population-level effect has ever been demonstrated. Both hold, and every claim below carries its own weakness.

Column A, 5 claims

Evidence for a diet effect

Cardiac function recovers after a diet change

Freeman 2022, JVIM. 60 DCM dogs, 16 subclinical, prospective

Fractional shortening improved significantly across nine months in dogs moved off nontraditional diets. Dogs carrying only subclinical abnormalities improved as well, which puts the effect within reach before end-stage disease.

LimitationsNine dogs in the comparison group, of which three completed. Echocardiographic readings were unblinded. The survival difference between groups, 611 days against 161, did not reach significance (P=.21). Purina funded.

The reversals are within-dog

Kaplan 2018, PLoS ONE. 24 Golden Retrievers, case series

Twenty-three of twenty-four improved on echocardiography. Of the eleven in congestive heart failure, nine cleared their congestion, five came off diuretics entirely and four halved the dose. Each dog serves as its own control, which strips out most of the confounding a population study carries. None of the implicated diets had passed AAFCO feeding trials.

LimitationsAll Golden Retrievers, all taurine deficient, all given taurine alongside the diet change, so the two interventions cannot be separated. The breed carries a known taurine-handling predisposition.

Thirty days of heavy legumes alters blood chemistry

Waltham 2022, BMC Vet Res. 11 Labradors, controlled feeding trial

At 60% legume inclusion, red cell count fell 7.7%, haematocrit 8.3% and phosphate rose 41.8%. Urinary taurine excretion dropped 77% while blood taurine still read normal. The authors then matched that signature against 420 clinical DCM records and found it mirrored.

LimitationsEleven dogs over thirty days, at a legume load above most commercial food. No cardiac changes were observed at all. Mars funded.

A mechanism candidate exists

Freeman 2024, AJVR. 53 dogs, biomarker study

Urinary di-22:6-BMP, an established marker of phospholipidosis, ran higher in dogs eating high-pulse diets and rose with the pulse load of the food. Electron microscopy showed lysosomal phospholipid accumulation resembling drug-induced phospholipidosis. After six years of no mechanism, this is a testable one.

LimitationsA correlation of 0.52 across 53 dogs, only four of them DCM cases on low-pulse diets. A biomarker is not a disease process, and the finding awaits independent replication.

Survival is longer when the diet is changed

Freid 2021, JVIM. 71 dogs, retrospective

Dogs taken off nontraditional diets reached a median survival of 337 days against 215 for those left on them (P=.002), alongside larger reductions in systolic left ventricular dimension and left atrial to aortic ratio. Walker 2022 found the same direction, with reduced furosemide and pimobendan dosages over time.

LimitationsRetrospective. Owners who change a dog’s food are plausibly the owners managing everything else well, and the response varied widely between individual dogs.

Column B, 6 claims

Evidence against a population effect

Exposure rose five-fold and diagnosis rates did not move

Frontiers 2022. 68,297 cardiology patients, 14 referral centers, 2000 to 2019

Grain-free sales went from $900 million in 2011 to $5.4 billion in 2019, and market share from 21.5% to 29%. Across twenty years of records at the institutions that diagnose DCM, the rate held at 3.90% of cardiology caseload with no trend in either direction (P=0.98). No account of a population-level effect has yet explained this.

LimitationsFourteen of 88 invited centers took part, breed identification was by appearance, and no individual diet histories were available. BSM funded.

Eighteen months on grain-free produced no cardiac change

J Anim Sci 2025. 60 dogs, double-blind randomized

Four balanced diets, one of them grain-free with 16.4% peas and 16.4% potatoes, followed for eighteen months with echocardiography, troponin I and NT-BNP. No dog developed DCM, no clinically significant biomarker change appeared, taurine held steady. This is the study design the FDA investigation lacked.

LimitationsSixty dogs cannot detect an event with a prevalence near 0.5%, no power analysis was run, and 16.4% peas sits well below the inclusion levels in the products that raised concern. Hill’s funded, Hill’s employees.

Pulses at 45% produced no cardiac effect

Singh 2023, J Nutr. 28 Siberian Huskies, 20 weeks, dose-response

Whole pulse inclusion tested at 0, 15, 30 and 45% in a complete and balanced diet with chicken meal and pea starch. Echocardiographic parameters, NT-proBNP and cardiac troponin I showed no difference among treatments or across time.

LimitationsOne breed, a well-formulated test diet, and three co-authors employed by Champion Petfoods. It asks whether pulses are inherently cardiotoxic, a different question from whether badly formulated pulse-heavy food harms a susceptible dog.

The reported dogs were predominantly predisposed breeds

FDA case data. 305 reports with breed recorded

223 of 305, or 73%, were Goldens, Great Danes, Dobermans, Boxers, Cockers or Bulldogs. Doberman DCM alone carries a cumulative prevalence near 40% in North America and close to 60% in Europe, with identified PDK4 and titin variants behind it.

LimitationsDiet-associated cases do also turn up in breeds with no predisposition, which is one of the observations that prompted the investigation in the first place.

Diagnosis and premium food sit behind the same paywall

FDA case data. Echocardiography $500 to $1,200 at referral

Diagnosing DCM requires echocardiography by a cardiologist, roughly $500 to $1,200 at a referral hospital, with a full outpatient cardiac evaluation running $700 to $1,000. Boutique and grain-free diets carry a price premium. Both track the owner’s disposable income, so the diet and the diagnosis share a cause: money. A dog eating an economy diet that dies suddenly is recorded as a death, never as a DCM case, and never enters the file. The FDA named the cost barrier as a driver of underreporting without addressing that it lines up with the diet under investigation.

ScopeThis reaches the FDA report pile alone. It leaves the referral-center incidence study intact, since numerator and denominator there are drawn from the same owners who already cleared the cost barrier, and it does not touch the within-dog reversals in Column A.

The investigation generated its own reports

FDA reporting curve, 2018 to 2022

Reports climbed after the 2018 announcement and the 2019 brand list, then fell to 255 across the final two and a half years. Voluntary reporting systems track publicity. The FDA separately acknowledged that breed-specific owner communities were organizing submissions.

LimitationsPublicity raising the report volume does not establish that the underlying events were unreal. It establishes that the count cannot be interpreted.

Where the science stands in 2026

The mainstream position has moved a long way from what the public was told, and it has moved toward a claim that leaves the original advice poorly aimed.

Lisa Freeman at Tufts is the most prominent proponent of a diet link and the author of the 2018 work that established the subject. She discloses funding from Hill’s, Purina and Royal Canin.

Her June 2026 update, drawing on more than thirty published studies, states that the disease does not appear to be caused by a lack of grains, and that nutritional deficiencies do not appear to play a major role.

What remains implicated is pulses at high inclusion, in grain-free and grain-inclusive food alike. The mechanism is still unidentified, with phospholipidosis the leading candidate.

The strongest advocate for a diet link and the strongest skeptics agree on one point: the grain-free designation was a label correlated with a formulation style, and never the operative variable.

Tufts Petfoodology, June 2026

That carries a practical consequence. Plenty of grain-inclusive food is pulse-heavy, so an owner who switched from a grain-free bag to a grain-inclusive one with peas and lentils high in the ingredient list changed the label and left the exposure where it was.

What can and cannot be claimed1 paragraph

Diet-associated DCM appears to be a real but uncommon phenomenon reaching a small number of dogs, likely through high pulse inclusion and an individual susceptibility nobody can currently predict, by a mechanism nobody has identified. In some dogs it reverses when the food changes, which is the strongest evidence in the file. It has never been demonstrated at population scale, and the surveillance data that prompted the investigation was incapable of demonstrating it. Both statements hold at once.

Unresolved questions

These are the gaps that let both sides overclaim.

01
Why only some dogs
Millions ate these diets without incident. No susceptibility marker has been found, so no individual dog’s risk can be assessed.
02
What the dose is
45% inclusion did nothing to Huskies over 20 weeks. 60% altered Labrador blood chemistry within thirty days. 16.4% did nothing over eighteen months. No threshold has been established, and no label discloses a pulse percentage anyway.
03
Whether the variable is the pulses or the manufacturer
Kaplan noted that none of the implicated diets had passed AAFCO feeding trials. Pulse-heavy formulation and small-manufacturer formulation were confounded in the original signal and largely remain so.
04
Whether phospholipidosis is cause, effect or coincidence
The 2024 biomarker finding is the strongest lead available and remains a correlation across 53 dogs awaiting independent replication.
05
What the incidence is
Unestablished in either direction. Passive reporting undercounts heavily, so a low report count demonstrates safety no better than it demonstrated harm.

Questions worth asking about any food

"Is grain-free dangerous" cannot be answered for an individual dog. These five track manufacturing quality, which is what the evidence actually implicates.

01
Does the manufacturer employ a qualified nutritionist full time?
A PhD in animal nutrition or a board-certified veterinary nutritionist, on staff rather than on retainer.
02
Do they run AAFCO feeding trials, or formulate to a profile on paper?
The distinction Kaplan flagged in 2018. It has aged better than the grain-free framing did.
03
Do they own and control their manufacturing?
Co-packing is not disqualifying. The answer shows how much of the process the brand governs directly.
04
Will they provide a full nutrient analysis on request?
The complete profile, not the guaranteed analysis printed on the bag.
05
Where do pulses sit in the ingredient list?
The question that matches the 2026 evidence, and it applies to grain-inclusive food just as much.

Scope

These questions do not require contradicting a veterinarian

None of them concerns grain content. A large established manufacturer with staff nutritionists and completed feeding trials answers all five well, with or without grain in the formula, so the underlying veterinary caution is satisfied without the diet category entering the conversation.

For a Golden Retriever, Doberman, Boxer, Great Dane or Cocker Spaniel, cardiac screening is indicated on genetic grounds independent of diet, and it is a concrete action to take back to the treating veterinarian.

Sources

FDA, Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy Final update 23 December 2022.
Kaplan JL, Stern JA, Fascetti AJ, et al. Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets PLoS ONE, 2018;13(12):e0209112. No specific funding.
Freeman LM, Rush JE, Adin D, et al. Prospective study of dilated cardiomyopathy in dogs eating nontraditional or traditional diets and in dogs with subclinical cardiac abnormalities JVIM, 2022;36(2):451. Funded by Nestlé Purina PetCare and the Barkley Fund.
Freid KJ, Freeman LM, Rush JE, et al. Retrospective study of dilated cardiomyopathy in dogs JVIM, 2021;35(1):58.
Walker AL, DeFrancesco TC, Bonagura JD, et al. Association of diet with clinical outcomes in dogs with dilated cardiomyopathy and congestive heart failure J Vet Cardiol, 2022;40:99 to 109.
Responses in randomized groups of healthy adult Labrador retrievers fed grain-free diets with high legume inclusion for 30 days display commonalities with dogs with suspected dilated cardiomyopathy BMC Vet Res, 2022. Funded by Mars Petcare; correction issued May 2022.
Incidence of Canine Dilated Cardiomyopathy Diagnosed at Referral Institutes and Grain-Free Pet Food Store Sales: A Retrospective Survey Frontiers in Animal Science, 2022. Funded by BSM Partners LLC.
Different carbohydrate sources in dog foods supported overall health and cardiac function: an 18-month prospective study in healthy adult dogs J Anim Sci, 2025. Funded by Hill’s Pet Nutrition.
Singh P, Banton S, Raheb S, et al. The Pulse of It: Dietary Inclusion of Up to 45% Whole Pulse Ingredients Does Not Affect Cardiac Function, Fasted Sulfur Amino Acid Status, or Other Gross Measures of Health in Adult Dogs J Nutr, 2023. PMID 36972833. Co-authors affiliated with Champion Petfoods and Protein Industries Canada.
McCauley SR, et al. Review of canine dilated cardiomyopathy in the wake of diet-associated concerns J Anim Sci, 2020;98(6). Corrigendum adding conflict-of-interest disclosure, 2020;98(7).
Freeman LM, Rush JE, Berridge BR, et al. Dogs with diet-associated dilated cardiomyopathy have higher urine di-docosahexaenoyl (22:6)-bis(monoacylglycerol)phosphate, a biomarker of phospholipidosis Am J Vet Res, 2024. doi:10.2460/ajvr.24.07.0211.
Freeman LM. Update on Diet-Associated Dilated Cardiomyopathy Tufts Petfoodology, 22 June 2026.
Mansilla WD, et al. Special topic: The association between pulse ingredients and canine dilated cardiomyopathy: addressing the knowledge gaps before establishing causation J Anim Sci, 2019;97(3):983.