Plain-English summary
Since 2018, when a link between grain-free diets and canine dilated cardiomyopathy was first raised publicly, dog owners have been asked to make a decision on evidence that is still being assembled.
This 2021 study looked at 188 healthy dogs of four breeds and compared those eating grain-free diets with those eating grain-inclusive ones. On the measures that describe the heart's structure and function — echocardiography — there were no differences. Taurine, the nutrient most often blamed, showed no deficiency in either group.
But one blood marker did differ. High-sensitivity cardiac troponin I, which rises when heart muscle cells are damaged, was higher in the dogs eating grain-free diets.
That is the whole finding: no visible difference in the heart, a hint of something in the blood. It is neither reassurance nor alarm, and presenting it as either would misrepresent it.
What the study found
The study was observational and cross-sectional, enrolling 188 healthy Doberman Pinschers, Golden Retrievers, Miniature Schnauzers and Whippets. Echocardiograms, cardiac biomarkers, and blood and plasma taurine were compared between dogs eating grain-free (n = 26) and grain-inclusive (n = 162) diets, and separately between dogs whose food listed peas, lentils or potatoes among the top ten ingredients (n = 39) and those whose food did not (n = 149). Comparisons controlled for age and breed.
No differences were found in echocardiographic variables, in N-terminal pro-B-type natriuretic peptide, or in whole blood taurine between diet types.
Dogs eating grain-free diets had a higher median high-sensitivity cardiac troponin I — 0.076 ng/mL (IQR 0.028–0.156) against 0.048 (IQR 0.0026–0.080) for grain-inclusive dogs (P < .001) — and higher median plasma taurine, 125 nmol/mL against 104 (P = .02).
Dogs eating diets with the flagged ingredients in the top ten had a higher median troponin than those without (0.059 against 0.048; P = .006), and a greater proportion had ventricular premature complexes during examination: 10% against 2% (P = .04).
The authors' conclusion is carefully bounded: higher troponin in healthy dogs eating these diets might indicate low-level heart-muscle injury.
For context on the other strand of this question, a 2018 case series described 24 golden retrievers with taurine deficiency and dilated cardiomyopathy, 23 of which were eating diets that were grain-free, legume-rich, or both. Twenty-three of the 24 improved on echocardiography and normalised their taurine after diet change and taurine supplementation.
What this study cannot tell you
The grain-free group was small — 26 dogs against 162. Differences based on a group that size warrant caution, and the confidence around those medians is correspondingly loose.
The design is cross-sectional and observational. Dogs were not randomised to diets; owners chose them. Owners who select grain-free food may differ in other ways that were not measured, and this design cannot separate diet from whoever chooses it.
Troponin is a marker, not an outcome. A higher median troponin in a group of dogs that all had normal echocardiograms is a signal worth pursuing, not evidence that any of those dogs will develop heart disease. No dog in this study was followed to see what happened next.
The four breeds studied were chosen partly for their known cardiac profiles, and results may not transfer to other breeds.
The golden retriever case series carries its own limits: 24 dogs, no control group, and diet change and taurine supplementation given together, so their separate contributions cannot be distinguished. It also describes taurine-deficient disease specifically, which is not what the 2021 study found in healthy dogs — these are two different pictures, and conflating them is a common error in coverage of this topic.
What pet owners should track
This is a topic where a clear record is more useful than an opinion:
- Exactly what your dog eats — brand, product name and formulation, not just "grain-free" — with the date you started it
- Every diet change, with dates, since diet history is the first thing a cardiologist will ask about
- Treats, chews and table food, which are routinely forgotten and can be a substantial share of intake
- Exercise tolerance, coughing, fainting or collapse, and any breathing change — the signs that would prompt cardiac investigation
- Any murmur or arrhythmia noted at a check-up, with the date
Do not change your dog's diet based on this article. Diet choice interacts with breed, life stage and any existing condition, and abrupt changes carry their own risks. Bring the question and your diet record to your veterinarian.
What PAWai can help organize
Diet history is exactly the kind of information that is trivial to record and almost impossible to reconstruct two years later — which is precisely when it gets asked for. PAWai keeps what your dog ate and when, alongside any cardiac findings from check-ups. PAWai does not evaluate diets, does not recommend or discourage any food, and does not assess heart health. Nutrition and cardiology are both veterinary domains, and this question in particular is unsettled enough that no app should be taking a position on it. What PAWai contributes is an accurate diet timeline for whoever does.
Disclaimer
PAWai organizes information and educates pet owners. PAWai does not diagnose conditions or recommend treatment. Always consult a licensed veterinarian for medical decisions about your pet.
Citation
Adin, D., Freeman, L., Stepien, R., Rush, J. E., Tjostheim, S., Kellihan, H., Aherne, M., Vereb, M., & Goldberg, R. (2021). Effect of type of diet on blood and plasma taurine concentrations, cardiac biomarkers, and echocardiograms in 4 dog breeds. Journal of Veterinary Internal Medicine, 35(2), 771–779. https://doi.org/10.1111/jvim.16075
Kaplan, J. L., Stern, J. A., Fascetti, A. J., Larsen, J. A., Skolnik, H., Peddle, G. D., et al. (2018). Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets. PLOS ONE, 13(12), e0209112. https://doi.org/10.1371/journal.pone.0209112