The grain free vs grain dog food debate is one of the most commercially charged arguments in dog nutrition — and one where marketing language has consistently run well ahead of the science. Dog food brands selling grain-free products implied that grains were unnatural, harmful, or inferior. Dog owners bought the premise. Then an FDA investigation complicated the picture significantly.
Table of Contents
Here is the honest, evidence-based position on grain-free vs grain-inclusive dog food — covering what the science actually shows, what the FDA investigation found and concluded, when grain-free is genuinely indicated, and what the real benchmark for any dog food should be.
Where Grain-Free Came From — The Marketing Origin
JustFoodForDogs provides the clearest account of how grain-free dog food became mainstream: the idea that dogs need high-protein, grain-free, meat-heavy diets only became mainstream in the last 10 to 15 years. It didn’t come from veterinary nutritionists. It came from human diet trends — paleo, ancestral eating, the general cultural moment of eating like our ancestors. Pet food marketers saw an opportunity, and the wolf imagery followed.
The core marketing argument was that dogs evolved from wolves, wolves don’t eat grains, therefore grains are unnatural for dogs. As covered in our Are Dogs Carnivores? article, this argument ignores the significant genetic and metabolic adaptations that occurred during domestication — particularly the AMY2B gene duplication that gives dogs significantly enhanced starch-digesting capacity compared to wolves. Dogs have been eating plant-based food scraps alongside humans for 15,000 to 40,000 years. The grain-free framing of dogs as wolves needing meat-only diets was always more marketing than biology.
Improve International, whose veterinary-authored content is used in continuing education for vets, is direct: most veterinary professionals have long felt that grain-free diets are a fad with no real evidence that they are better than grain-inclusive diets.
Are Grains Bad for Dogs? The Honest Answer
No — for the vast majority of dogs, grains are not bad. They are not harmful, not unnatural in the context of domestication, and not nutritionally inferior to grain-free alternatives.
Grains dogs tolerate well include: oats, brown rice, barley, millet, quinoa, and whole wheat. These provide digestible carbohydrates for energy, dietary fibre for gut health, B vitamins, iron, and other useful micronutrients.
Are grains hard for dogs to digest? No. As covered in our Are Dogs Omnivores? article, dogs digest cooked starches with over 90% efficiency — directly comparable to human starch digestion. The AMY2B gene evidence from the landmark 2013 Nature study confirms this adaptation.
Do grains cause allergies in most dogs? No — this is the most persistent myth driving grain-free purchases. JustFoodForDogs is explicit: grain-free food is not an effective solution for most dog allergies, as the majority of canine food allergies are caused by protein sources such as chicken, beef, or dairy — not grains. A vet-supervised elimination diet is the only reliable way to identify the actual allergen. Most dogs who appear to improve on grain-free food do so because the protein source changed, not because grains were removed.
Is corn just a cheap filler? This is another persistent marketing claim. As confirmed in our Can Dogs Eat Corn Kernels? guide, corn provides linoleic acid (an essential fatty acid), antioxidants, and digestible carbohydrate. It is not nutritionally empty — the AKC confirms many veterinary nutritionists agree that corn for dogs is not a problem and can be part of a well-balanced diet.
The FDA Investigation — What Actually Happened
This is the most important and most misrepresented aspect of the grain-free debate, and it requires clear, accurate reporting.
July 2018: The FDA announced it was investigating a potential link between grain-free diets and dilated cardiomyopathy (DCM) — a serious heart condition that causes the heart to enlarge and lose its ability to pump blood effectively. Cases of DCM were appearing in breeds not traditionally predisposed to the condition, and many affected dogs were eating grain-free diets high in legumes (peas, lentils) and potatoes.
The concern: DCM is associated with taurine deficiency. The working hypothesis was that the amino acid precursors to taurine were less bioavailable from legume-heavy diets, or that high legume content was interfering with taurine synthesis or absorption. Houndsy’s veterinary-reviewed content notes that a 2018 study highlighted taurine deficiency as a concern particularly in Golden Retrievers on grain-free diets, and that over 90% of dogs with reported DCM cases had been eating grain-free food containing high levels of legumes.
December 2022: The FDA closed the investigation without finding a causal link and without issuing recalls or warnings against grain-free diets. The AKC confirms the FDA’s conclusion: there is no scientific evidence proving that grain-free diets cause DCM. The FDA stated it would not release further public updates unless meaningful new scientific information emerged.
What the investigation revealed: DCM is a complex condition influenced by multiple factors including genetics, breed predispositions, and overall diet formulation. The cases were not straightforwardly attributable to grain-free feeding alone.
The important nuance — it was never just about grains: JustFoodForDogs identifies the key distinction that much of the public debate missed. The FDA investigation focused on what it called “BEG diets” — boutique, exotic ingredient, and grain-free diets. The concern was not simply the absence of grains. It was the combination of:
- Boutique manufacturers without the nutritional research infrastructure of established brands
- Exotic protein sources (kangaroo, bison, alligator) with less established nutritional profiles
- High legume content (peas, lentils, chickpeas) as a primary carbohydrate substitute
- Grain-free formulation
A grain-free diet from a well-established manufacturer with robust nutritional research and appropriate ingredient sourcing presents a fundamentally different risk profile from a boutique grain-free product with peas as the first or second ingredient. The nuance matters.
What Improve International’s Evidence Review Found
Improve International’s vet-authored evidence review provides the most balanced academic assessment available. Their conclusions, presented to veterinary professionals:
- There are a couple of small-scale studies showing grain-free diets are more palatable than grain-inclusive diets
- There is some evidence they reduce postprandial glucose, which may benefit diabetic dogs
- Gluten sensitivity is very rare in dogs — genuine gluten intolerance exists in Border Terriers with paroxysmal dyskinesia and potentially in Irish Setters, but is not a widespread canine condition
- Any benefit from switching to grain-free is likely coincidental — most apparent improvements are explained by the change in protein source, not the removal of grains
- Research into diet-associated DCM is continuing — the FDA closure does not mean the investigation is entirely resolved, it means causality was not established with the available evidence
The practical takeaway from the veterinary evidence review: grain-free diets have no proven benefit for most dogs, some concerning signals remain (particularly for high-legume formulations), and the apparent benefits owners observe when switching are most likely attributable to protein source changes or simply the novelty of a new food.
When Grain-Free Is Genuinely Indicated
The evidence base supports grain-free feeding in specific, defined circumstances:
True grain allergy or confirmed grain sensitivity — rare but real. If a veterinarian has conducted a proper elimination diet trial and confirmed that your dog reacts to grains specifically, a grain-free diet is appropriate. JustFoodForDogs confirms this is the only scenario where grain-free is genuinely indicated — and it should always be implemented under strict veterinary supervision.
Gluten-sensitive Border Terriers — paroxysmal dyskinesia in Border Terriers has been specifically associated with gluten sensitivity. Grain-free or gluten-free diets have documented benefit in this specific condition.
Diabetic dogs with postprandial glucose concerns — Improve International notes the evidence of reduced postprandial glucose on grain-free diets may benefit diabetic dogs. A vet recommendation is essential here.
Specific gastrointestinal conditions — some dogs with chronic digestive conditions respond better to grain-free diets. As with all medical dietary decisions, this should be made with veterinary guidance.
For all other healthy dogs without these specific conditions, grain-free offers no proven benefit and carries the BEG diet concern for legume-heavy formulations.
What Actually Matters — AAFCO Standards
The grain-free vs grain-inclusive debate has distracted from what the evidence consistently identifies as the most important consideration in dog food selection: nutritional completeness and adequacy, as defined by AAFCO standards.
AAFCO (Association of American Feed Control Officials) sets the nutritional adequacy standards for dog food in the US. A food labelled “complete and balanced” and meeting AAFCO standards for the appropriate life stage has been assessed as nutritionally adequate for dogs at that stage — regardless of whether it contains grains.
The AKC and Improve International both reach the same conclusion: the key is not whether a food is grain-free or grain-inclusive. The key is whether it meets AAFCO nutritional standards, comes from a manufacturer with robust nutritional research and quality control, and is appropriate for your dog’s individual life stage, health status, and specific needs.
Quest Quip’s veterinary nutrition commentary captures the current consensus: veterinary nutritionists and cardiologists emphasise choosing companies with strong research, quality control, and transparent formulation practices — rather than focusing solely on marketing terms such as grain-free or boutique.
How to Evaluate Any Dog Food — The Practical Framework
Whether grain-free or grain-inclusive, apply this framework before choosing a dog food:
1. AAFCO statement — look for “complete and balanced” for your dog’s specific life stage (puppy, adult, all life stages). This is the minimum standard.
2. Manufacturer nutritional research — does the brand employ veterinary nutritionists? Have they conducted feeding trials? Do they have published research? Large established manufacturers (Purina, Hill’s, Royal Canin, Eukanuba) have extensive research infrastructure. Boutique brands often do not.
3. Ingredient list perspective — the first five ingredients make up the majority of the food. Named protein sources (chicken, beef, salmon) first is positive. High levels of peas, lentils, or chickpeas as primary carbohydrate substitutes warrants consideration in the context of the DCM investigation.
4. Your vet’s knowledge of your specific dog — breed, age, health status, activity level, and any specific conditions all affect the right food choice. No general article replaces a vet who knows your dog.
5. Watch your dog — coat condition, energy level, stool quality, and body weight are the practical indicators of whether a food is working for your individual dog.
The Natural Treats Angle — How This Applies to Treats
The grain-free vs grain-inclusive debate is primarily a dog food discussion, but it has practical implications for natural treats too.
Most high-quality natural treats are naturally grain-free — they are single-ingredient dried or freeze-dried meat, fish, or organ products. Beef liver treats, dried salmon skins, air-dried chicken, bully sticks — none of these contain grains, and none need to. Their grain-free status is a consequence of what they are, not a marketing claim.
This is meaningfully different from grain-free dog food that replaces grains with large quantities of peas or lentils as a primary ingredient. A piece of freeze-dried chicken heart contains no grains, no legumes, and no carbohydrate — it is simply dried chicken heart. The DCM concern from the FDA investigation does not apply to this kind of natural treat use.
For grain-based treats — rice-based chews, oat-based biscuits — the evidence does not suggest these cause harm in healthy dogs. Applied to treats within the 10% daily calorie guideline, grain-containing treats present no meaningful health concern for most dogs.
Browse our Are Dog Treats Healthy? guide for the complete framework on choosing quality treats regardless of their grain content.
The Bottom Line
Grain-free dog food is not superior to grain-inclusive dog food for most dogs. The marketing premise — that grains are unnatural, harmful, or that dogs need to eat like wolves — was never well-supported by veterinary science. The majority of dogs have no issue with well-prepared grains as part of a complete and balanced diet.
The FDA’s DCM investigation raised legitimate concerns about high-legume, boutique, grain-free formulations specifically — not about grain-free as a universal category, and not about high-quality grain-free diets from established manufacturers. The FDA closed the investigation in December 2022 without establishing causality, but the signal from legume-heavy BEG diets remains a reason for caution with that specific subset.
For most dogs, the right food is one that meets AAFCO standards for their life stage, comes from a manufacturer with credible nutritional research, contains named protein sources, and suits your dog’s individual health and preferences. Whether that food contains grains or not is a secondary consideration.
Consult your veterinarian. Feed a complete and balanced diet. The grain-free label is a marketing decision — nutritional completeness is what actually matters.
Frequently Asked Questions
Is grain-free dog food better than grain-inclusive? Not for most dogs. There is no proven benefit of grain-free over grain-inclusive for healthy dogs without grain sensitivity. Improve International’s veterinary evidence review concludes that any apparent improvement when switching to grain-free is most likely due to the protein source change, not the removal of grains.
Did the FDA prove that grain-free food causes heart disease? No — the FDA closed its investigation in December 2022 without establishing a causal link between grain-free diets and DCM. The concern remains specifically with legume-heavy BEG (boutique, exotic, grain-free) diets, not with grain-free as a universal category.
Do dogs have grain allergies? Genuine grain allergies exist but are uncommon. Most canine food allergies are caused by protein sources (chicken, beef, dairy) — not grains. A proper veterinary elimination diet trial is the only way to identify the actual allergen.
Are grains good or bad for dogs? Grains are neither inherently good nor bad — they are a source of carbohydrates, fibre, and some nutrients that most dogs can digest effectively. The key is the overall nutritional profile of the food, not the presence or absence of grains.
When is grain-free dog food appropriate? For dogs with confirmed grain allergy (rare, requires proper elimination diet), Border Terriers with paroxysmal dyskinesia and gluten sensitivity, and specific gastrointestinal conditions under veterinary guidance.
What should I look for in dog food? AAFCO complete and balanced statement for your dog’s life stage, a manufacturer with nutritional research infrastructure, named protein sources in the first ingredients, and a vet recommendation for your individual dog’s specific needs.
Sources:
- American Kennel Club — grain-free diet alert and DCM: best approach is consulting your veterinarian; weighing pros and cons of grain-inclusive vs grain-free; monitoring for DCM signs; FDA found no scientific evidence proving grain-free diets cause DCM (akc.org): https://www.akc.org/expert-advice/nutrition/fda-grain-free-diet-alert-dcm/
- JustFoodForDogs (veterinarian-authored) — grain-free trend came from human paleo/ancestral diet marketing; FDA investigations linked BEG diets to DCM; grain-free food not effective for most dog allergies as majority of canine food allergies are protein-sourced not grain-sourced; grain-free only genuinely indicated for confirmed grain allergy under strict veterinary supervision (blog.justfoodfordogs.com): https://blog.justfoodfordogs.com/grain-inclusive-dog-food.html
- Improve International (vet-authored CPD content) — most veterinary professionals feel grain-free diets are a fad with no real evidence they’re better than grain-inclusive; some palatability evidence; postprandial glucose reduction may benefit diabetic dogs; gluten sensitivity very rare in dogs; FDA announced no causal link in December 2022 (improveinternational.com): https://improveinternational.com/uk/grain-free-diets-and-pet-health/
- US Food and Drug Administration (FDA) — investigation into diet-associated DCM in dogs began July 2018; December 2022 announcement: adverse event numbers do not supply sufficient data to establish a causal relationship; FDA does not intend to release further public updates unless meaningful new scientific information emerges (fda.gov)
- Houndsy (veterinary-reviewed) — over 90% of dogs with reported DCM cases had been eating grain-free food with high legume content; 2018 study highlighted taurine deficiency concern particularly in Golden Retrievers; DCM complex condition influenced by genetics, breed predispositions, and overall diet formulation (houndsy.com): https://www.houndsy.com/blogs/modern-tails/is-grain-free-dog-food-best-a-deep-dive-into-pros-cons-and-vet-insights
For the canine diet evolution context behind this debate, see our Are Dogs Carnivores? and Are Dogs Omnivores? articles. For natural treat guidance that sidesteps the grain-free debate entirely, see our Are Dog Treats Healthy? guide — or browse our Can Dogs Eat series for guidance on specific safe and nutritious foods.