"Twenty-three of 24 dogs diagnosed with taurine deficiency and dilated cardiomyopathy were fed diets that were either grain-free, legume-rich, or a combination of these factors. … Twenty-three of 24 dogs had significant improvement in their echocardiographic parameters and normalization of taurine concentrations following diet change and taurine supplementation."
Do grain-free diets cause DCM?
In 2018 the FDA flagged a possible link between grain-free diets and dilated cardiomyopathy (DCM), a serious heart condition. Years later it is still unsettled. Here is the strongest evidence on each side, every study graded for design and funding.
What kind of evidence is this?
Mostly observational
Mostly case series and short feeding trials, with two industry-funded controlled studies and no large, independent randomized trial on either side.
Where the evidence stands today
Real cases exist, but causation has never been proven. Dogs with no genetic risk have developed DCM on grain-free, legume-heavy diets and often improved after switching. Still, no controlled trial shows the cause, and the FDA closed its investigation in 2022 citing insufficient data.
The case for a link
The strongest reasons to take the concern seriously.
"Non-traditional diets, which were typically grain-free and contained legumes in this study, were significantly associated with and have increased relative risk for the identification of taurine deficiency and echocardiographic abnormalities consistent with nutritionally-mediated DCM."
"Dietary-associated DCM occurs with some GF diets and can improve with nutritional management, including diet change."
Across 188 healthy dogs there were no differences in echocardiograms, NT-proBNP, or whole-blood taurine between diet types, while grain-free diets showed a higher median cardiac troponin I, a marker of heart-muscle stress.
Blood metabolite profiles differed between dogs on grain-free and grain-inclusive diets, and the study states the relevance of those differences to cardiac disease remains undetermined.
"Seventeen metabolites differed significantly in dogs with DCM eating NT versus traditional diets (e.g., fatty acids, amino acids, legume biomarkers), suggesting different mechanisms for primary versus diet-associated DCM."
"Mean 2D ejection fraction (EF) was lower for dogs eating nontraditional diets (48.65 ± 7.42%) vs dogs eating traditional diets (56.65 ± 4.63%; P < .001…)."
"Decreased hs-cTnI and LVIDsN in GF dogs after diet change supports reversibility of these subclinical myocardial abnormalities."
"Improvement in fractional shortening over time was significantly associated with previous consumption of a NTD, even after adjustment for other variables (P = .005)."
"Survival time was significantly longer for dogs with DCM eating nontraditional diets that had their diets changed (median survival, 337 days; range, 9-1307 days) compared to dogs eating nontraditional diets that did not have their diets changed (median survival, 215 days; range, 1-852 days; P = .002)."
"Overall, DCM-like changes observed with the wrinkled pea diet, but not lentil diet, after only 4 weeks in a breed not known to be susceptible support a link between pea-based diets and canine nutritionally-mediated DCM."
"Thus grain-free, legume-rich Test diets caused reduced RBC and hyperphosphatemia, findings also indicated in dogs with suspected DCM."
"A reduced cardiac function along with the greatest increase in NT-proBNP was observed after feeding the husbandry diet that contained the highest amount of insoluble fiber but did not contain legumes or oligosaccharide."
The case against a link
The strongest reasons the connection may be overstated.
"The use of the acronym ‘BEG’ and its association with DCM are without merit because there is no definitive evidence in the literature."
"The average incidence rate of DCM, amongst referral cases seen in the participating hospitals, was 3.90% (range 2.53–5.65%), while grain-free diet sales increased from 2011 to 2019."
"The results from this study suggest that increasing the inclusion of pulses up to 45% with the removal of grains and equal micronutrient supplementation does not impact cardiac function concurrent with dilated cardiomyopathy, body composition, or SAA status and is safe for healthy adult dogs to consume when fed for 20 wks."
"These data suggest that feeding APS, a grain-free diet, over a 26-wk period improved taurine status in Labrador Retrievers and is not the basis for the incidence of DCM for dogs fed APS."
"These data demonstrate that cardiac function was supported in healthy adult dogs fed foods formulated to provide similar nutrition through different ingredient profiles."
The FDA closed its investigation in 2022, citing insufficient data to establish causation.
How we grade evidence
Not all studies carry the same weight. We grade each by design, strongest to weakest:
- Randomized trial. Dogs are assigned to diets and compared. The strongest design for showing cause.
- Cohort or cross-sectional study. Dogs are observed, not assigned, so it can show a link but not a cause.
- Case series or survey. A set of real cases or reports, with no comparison group.
- Case report or opinion. A single account or an expert's view.
We also tag who funded each study. Funding does not make a finding wrong, but it tells you whose interpretation to scrutinize, and we tag it on both sides.