The Truth About Grain-Free Diets: What the FDA Studies Actually Found

In July 2018, the FDA issued an announcement that sent shockwaves through the pet food industry. They were investigating a potential link between grain-free diets and dilated cardiomyopathy (DCM)—a serious heart condition—in dogs. For the next three years, the investigation dominated headlines, sparked lawsuits, and divided the veterinary community. Now, with the FDA’s investigation largely concluded, we can finally look at what the data actually said—and what it didn’t.

The Initial Investigation

The FDA investigation began after cardiologists at veterinary teaching hospitals noticed an unusual spike in DCM cases. DCM is a disease where the heart muscle becomes enlarged and weakened, reducing its ability to pump blood. It’s historically been associated with specific breeds (Dobermans, Great Danes, Boxers) and taurine deficiency. But the new cases were appearing in breeds not typically prone to DCM—Golden Retrievers, Labradors, and mixed breeds.

What linked these cases was diet. The affected dogs were predominantly eating grain-free diets, often containing high concentrations of peas, lentils, chickpeas, and potatoes as carbohydrate sources. By 2019, the FDA had received 524 reports of DCM, with 560 dogs affected and 119 deaths. The grain-free diet association was striking: 93% of reported diets were grain-free, despite grain-free diets representing only about 20-30% of the market at the time.

What the FDA Actually Concluded

In December 2022, the FDA released its final update on the investigation. The conclusion was nuanced—and widely misreported by the media. The FDA did not find that grain-free diets cause DCM. What they found was a correlation between certain diets and DCM in some dogs, and the correlation was strongest in diets that substituted legumes (peas, lentils, chickpeas) for grains. The mechanism remains unknown.

The FDA explicitly stated: “The FDA does not advise any dietary changes based solely on the information we have gathered. Pet owners should consult their veterinarians for advice on their pet’s diet.” This was a far more cautious statement than the headlines suggested. The FDA also noted that many dogs eating grain-free diets never developed DCM, and that DCM is a multifactorial disease with genetic, metabolic, and environmental components.

What the Veterinary Nutrition Community Thinks Now

The American College of Veterinary Nutrition (ACVN) and the World Small Animal Veterinary Association (WSAVA) have issued guidelines that reflect the current consensus. The WSAVA’s 2024 nutrition guidelines state: “There is no evidence that grains are inherently harmful to dogs. The decision to feed grain-free should be based on individual dietary needs rather than marketing trends.”

Dr. Lisa Freeman, a veterinary nutritionist at Tufts University who has published extensively on DCM, emphasizes that the issue isn’t “grains vs. grain-free” but rather the overall nutritional adequacy of the diet. Many grain-free diets, particularly boutique and exotic formulations, have not undergone AAFCO feeding trials. They meet nutritional profiles on paper but may not perform well in practice.

Key Takeaways

• 93% of DCM cases in the FDA investigation involved grain-free diets, but correlation is not causation
• The FDA did not conclude that grain-free diets cause DCM; the mechanism remains unknown
• The correlation was strongest in diets high in peas, lentils, and chickpeas
• Grains are not inherently harmful to dogs; the issue is overall nutritional adequacy
• Choose diets that have undergone AAFCO feeding trials, regardless of whether they contain grains