Grain-free dog food has been one of the most significant commercial trends in pet nutrition over the past fifteen years. At its peak, grain-free products accounted for more than 40% of all premium dog food sales in the United States. Marketing positioned these products as more natural, closer to a dog's ancestral diet, and superior for dogs with allergies or sensitivities. Then, in July 2018, the U.S. Food and Drug Administration began an investigation that changed the conversation dramatically — a possible link between grain-free diets and a form of heart disease in dogs had emerged from veterinary cardiology reports.
Understanding what grain-free food actually is, what replaced the grains, what the FDA investigation found, and what the current evidence says is essential for any dog owner navigating the pet food aisle.
What Does "Grain-Free" Actually Mean?
Grain-free dog food is exactly what it sounds like: dog food formulated without cereal grains. The grains excluded from these products include wheat, corn, rice, barley, oats, rye, and sorghum — all of which have historically been common components of commercial dry dog food.
What grain-free dog food does NOT mean is low-carbohydrate. This is the most important and most widely misunderstood aspect of grain-free nutrition.
Dry extruded kibble requires a starchy carbohydrate source to form the pellet matrix during processing. When grains are removed, something must take their place. In the vast majority of grain-free products, that something is one or more of the following:
- Peas
- Lentils
- Chickpeas (garbanzo beans)
- Green peas / split peas
- Pea protein / pea starch
- Potatoes
- Sweet potatoes
- Tapioca
These ingredients are legumes and tubers — not grains — but they are high in carbohydrates. Potatoes contain approximately 85% carbohydrate by dry matter. Peas contain approximately 60-65% carbohydrate by dry matter. A grain-free kibble made with these ingredients can contain as much or more total carbohydrate as a conventional grain-inclusive kibble.
The key difference is not carbohydrate content but starch source. Grain-free advocates argue that legumes and potatoes are more digestible and less allergenic for dogs than grains. Whether this is clinically meaningful for most dogs is discussed below.
The FDA Dilated Cardiomyopathy Investigation
In July 2018, the FDA Center for Veterinary Medicine issued an alert describing an apparent increase in reports of dilated cardiomyopathy (DCM) in dog breeds not typically predisposed to the condition. This alert prompted a formal investigation that has generated significant scientific discussion, controversy, and ongoing research.
What is dilated cardiomyopathy (DCM)? Dilated cardiomyopathy is a disease in which the heart muscle weakens and the heart's chambers enlarge (dilate), reducing the organ's ability to pump blood effectively. It can cause congestive heart failure and sudden death. DCM has known genetic associations in certain large breeds — Doberman Pinschers, Great Danes, Boxers, and Irish Wolfhounds are among the breeds with documented hereditary DCM.
What did the FDA investigation find? Between July 2018 and December 2022, the FDA received more than 1,100 reports of suspected diet-associated DCM. The affected dogs included breeds not typically predisposed to DCM, such as Golden Retrievers, Labrador Retrievers, and mixed breeds. A substantial proportion of the affected dogs had been eating grain-free diets for an extended period. Among the brands most frequently implicated were several popular grain-free manufacturers using legume-heavy formulations.
Importantly, the affected dogs were eating diets with large amounts of peas, lentils, or potatoes in the first few ingredients — the highest-volume ingredients by weight in the formula.
The taurine deficiency hypothesis. One proposed mechanism linking grain-free diets to DCM involves taurine. Some dogs — particularly Golden Retrievers — appeared to have low blood taurine levels alongside their DCM diagnosis. Taurine is an amino acid involved in cardiac function. In the 1980s, taurine deficiency was identified as a cause of DCM in cats (leading to mandatory taurine supplementation in cat food). A similar mechanism in dogs was hypothesised.
The connection to grain-free diets is indirect: legumes like peas and lentils contain compounds (phytates, fibre, and terpene glycosides) that may interfere with taurine synthesis or bioavailability in some dogs. This hypothesis has not been confirmed, and taurine deficiency was not present in all affected dogs, making it at most a partial explanation.
Where does the investigation stand in 2025? As of 2025, the FDA has not established a confirmed causal link between grain-free diets and DCM. The investigation is ongoing. Key challenges in the research include:
- DCM is underdiagnosed in dogs because cardiac monitoring is not routine
- The increase in reports may partly reflect increased veterinary awareness rather than a true disease increase
- Confounding factors (breed, age, genetics, other dietary factors) are difficult to control
- Causal mechanisms remain unproven
However, several prominent veterinary cardiologists — including groups at Tufts University Cummings School of Veterinary Medicine — have issued guidance recommending that certain breeds avoid grain-free, legume-heavy diets as a precaution, particularly breeds already predisposed to DCM.
Breeds at Higher Risk
Based on the patterns observed in the FDA investigation and subsequent research, the following breeds are considered higher risk and are most commonly cited in cardiologist recommendations to avoid grain-free, legume-heavy diets:
- Golden Retrievers
- Labrador Retrievers
- Miniature and Standard Schnauzers
- Cocker Spaniels
- American Cocker Spaniels
- Irish Wolfhounds
- Doberman Pinschers
- Boxers
- Saint Bernards
- Portuguese Water Dogs
For these breeds, most veterinary cardiologists recommend feeding a diet that includes grains and avoids large amounts of peas, lentils, and potatoes as primary ingredients.
Are Grain Allergies Common in Dogs?
One of the primary marketing arguments for grain-free diets is that grains cause allergies or sensitivities in dogs. The evidence does not support this framing.
True food allergies in dogs — involving an immunological response — are relatively uncommon. They affect an estimated 0.1-1% of the dog population. When food allergies do occur in dogs, the most common triggers are not grains. Multiple studies, including a landmark review published in Veterinary Dermatology, found that the most common food allergens in dogs are animal proteins:
- Beef (most commonly reported)
- Dairy
- Chicken
- Wheat
- Egg
- Lamb
- Soy
- Corn
Wheat is on this list, but it accounts for a smaller percentage of canine food allergies than beef, dairy, or chicken. Corn and rice, which are among the most commonly marketed-against grains, rank lower still.
The clinical implication is that most dogs marketed as having "grain sensitivities" do not have immunological reactions to grains. A dog with genuine dietary allergies causing skin or GI symptoms is more likely to be reacting to the animal protein in their food than to the grain.
For a dog with suspected food allergies, the appropriate diagnostic approach is a strict hydrolysed protein or novel protein elimination diet trial of 8-12 weeks, supervised by a veterinarian — not a switch to grain-free food.
Grain-Free vs Grain-Inclusive: Ingredient Comparison
| Aspect | Grain-Free (Legume-Based) | Grain-Inclusive (Standard) |
|---|---|---|
| Primary carbohydrate source | Peas, lentils, chickpeas, potatoes | Rice, oats, barley, corn |
| Total carbohydrate content | Typically 30-50% DM | Typically 40-60% DM |
| Protein content | Similar | Similar |
| Fat content | Similar | Similar |
| DCM investigation link | Yes (legume-heavy varieties) | Not implicated |
| Grain allergy suitable | Yes (for true grain allergy — rare) | No |
| Typical premium price | Higher | Lower |
| AAFCO compliant options | Yes | Yes |
Reading a Grain-Free Ingredient Label
If you are evaluating a grain-free product, the key is ingredient order. Pet food ingredient labels list components in descending order by pre-cooking weight. If peas, lentils, chickpeas, pea protein, or pea starch appear in the first five ingredients, the product is high in legumes and falls squarely within the category associated with the FDA investigation.
A grain-free product with a named meat (chicken, beef, salmon) as the first ingredient, followed by limited quantities of legumes or potatoes lower in the ingredient list, is a different product with a different risk profile than one where legumes dominate the top ingredients.
Examples of ingredient labels (simplified for illustration):
High legume grain-free (higher concern): Chicken meal, peas, lentils, pea protein, pea starch, chickpeas, chicken fat...
Lower legume grain-free (lower concern): Deboned chicken, chicken meal, chicken fat, sweet potato, potatoes, salmon oil, tapioca starch...
Grain-Free and Low-Carbohydrate Are Not the Same
This distinction bears repeating because it is so frequently confused in marketing and consumer discussions.
A dog eating a grain-free kibble may be eating as much or more carbohydrate as a dog eating a grain-inclusive kibble. Peas and potatoes are high-carbohydrate foods.
If a dog owner's goal is genuinely reducing dietary carbohydrate — for weight management, diabetes, or other medical reasons — a raw diet, a wet food, or a specifically formulated low-carbohydrate diet (verified by nutrient analysis, not just by the absence of grains) is more likely to achieve that goal than simply switching to grain-free kibble.
Conversely, if a dog owner's goal is simply avoiding wheat gluten specifically, there are grain-inclusive options that exclude wheat while retaining rice or oats, which are less commonly implicated in food allergies.
What the Tufts Cardiology Position Actually Says
The Cummings School of Veterinary Medicine at Tufts University has published publicly accessible guidance that is frequently cited in this discussion. Their position (as of the most recent updates) is as follows:
- They recommend avoiding diets in which peas, lentils, legumes, or potatoes appear in the first five ingredients, particularly for breeds predisposed to DCM
- They do not state that all grain-free foods are dangerous or that all grain-inclusive foods are safe
- They recommend regular cardiac monitoring for breeds predisposed to DCM regardless of diet
- They acknowledge that the causal link between grain-free diets and DCM has not been proven
This is a nuanced position. It is not a blanket condemnation of grain-free food, but it is a specific recommendation against legume-heavy formulations for at-risk breeds — which includes many of the most popular large breeds in North America.
Practical Guidance for Dog Owners
For breeds predisposed to DCM (Golden Retrievers, Dobermans, etc.): Follow cardiologist guidance and choose grain-inclusive diets or grain-free diets with minimal legume content (legumes not in the first five ingredients). Have the dog's heart assessed by a veterinarian or veterinary cardiologist regularly as the breed ages.
For dogs with suspected food allergies: Conduct a proper elimination diet trial under veterinary supervision. Do not assume grains are the cause. The allergen is more likely to be an animal protein.
For dogs without any specific health concerns: The majority of dogs do well on high-quality, AAFCO-compliant diets whether grain-free or grain-inclusive. The decision should be guided by the specific product's ingredient quality and nutritional completeness rather than by the grain-free label alone.
For dog owners simply attracted to "natural" or "ancestral" diets: A high-quality grain-inclusive diet from a reputable manufacturer with meat as the first ingredient is likely to be equally or more nutritionally appropriate than a low-quality grain-free alternative.
Cross-Links and Related Articles
- Raw Diet for Dogs: Pros and Cons
- How Much to Feed a Dog by Weight
- Senior Dog Nutrition Guide
- Labrador Retriever
- Golden Retriever
- Wet vs Dry Dog Food: Which Is Better
References
Adin D, et al. "Echocardiographic phenotype of canine dilated cardiomyopathy differs based on diet type." Journal of Veterinary Cardiology. 2019;21:1-9. doi:10.1016/j.jvc.2018.11.002
U.S. Food and Drug Administration. "FDA Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy." FDA Alert, June 2019 (updated 2022). fda.gov
Verlinden A, et al. "Food hypersensitivity reactions in dogs and cats: a review of 251 owner-reported cases." Veterinary Dermatology. 2006;17(3):195-202. doi:10.1111/j.1365-3164.2006.00515.x
Kaplan JL, et al. "Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets." PLOS ONE. 2018;13(12):e0209112. doi:10.1371/journal.pone.0209112
Freeman LM, et al. "Diet-associated dilated cardiomyopathy in dogs: what do we know?" Journal of the American Veterinary Medical Association. 2018;253(11):1390-1394. doi:10.2460/javma.253.11.1390
Cummings Veterinary Medical Center at Tufts University. "Diet and Heart Disease in Dogs." Tufts Cardiology, 2023. vetmed.tufts.edu
Frequently Asked Questions
Is grain-free dog food dangerous?
Grain-free dog food containing large amounts of legumes (peas, lentils, chickpeas) or potatoes in the top ingredients has been associated with increased reports of dilated cardiomyopathy (DCM) in dogs since 2018. The FDA is investigating a potential link but has not established confirmed causation. For breeds predisposed to DCM (Golden Retrievers, Cocker Spaniels, Dobermans), veterinary cardiologists recommend avoiding legume-heavy grain-free diets as a precaution.
What replaced the grains in grain-free dog food?
Most grain-free dog food replaces grains with peas, lentils, chickpeas, pea protein, pea starch, potatoes, sweet potatoes, or tapioca. These are high-carbohydrate ingredients, so grain-free food is not low-carbohydrate. The kibble still requires a starchy binder for the extrusion process.
Do dogs have grain allergies?
True grain allergies in dogs are rare — affecting roughly 0.1-1% of dogs. When food allergies do occur, the most common triggers are animal proteins (beef, dairy, chicken, lamb) rather than grains. Wheat is a documented allergen, but corn and rice rarely cause true allergic responses. Most dogs marketed as 'grain sensitive' do not have immunological grain allergies.
What is the link between grain-free food and DCM?
The FDA began investigating grain-free diets and dilated cardiomyopathy (DCM) in 2018 after veterinary cardiologists reported DCM in breeds not typically predisposed to the condition. The proposed mechanism involves taurine deficiency — compounds in legumes may interfere with taurine synthesis in some dogs, and taurine is important for cardiac muscle function. As of 2025, no confirmed causal relationship has been established, but the investigation is ongoing.
Which dog breeds should avoid grain-free food?
Breeds most commonly recommended to avoid legume-heavy grain-free diets by veterinary cardiologists include Golden Retrievers, Labrador Retrievers, Cocker Spaniels, Miniature and Standard Schnauzers, Doberman Pinschers, Boxers, and Irish Wolfhounds. These breeds are either already predisposed to DCM genetically or appeared disproportionately in FDA investigation reports.
How do I know if a grain-free dog food is high in legumes?
Read the ingredient label. Pet food ingredients are listed in descending order by pre-cooking weight. If peas, lentils, chickpeas, pea protein, or pea starch appear in the first five ingredients, the product is high in legumes and falls within the dietary pattern associated with the FDA DCM investigation. Legumes lower in the ingredient list (after several meat-based ingredients) are less of a concern.