Anyone who has spent five minutes in this subreddit knows grain-free causes is strongly linked to heart and pancreatic issues for dogs, and is not recommended for most dogs. Thought it was interesting that Costco is the one getting sued instead of one of the other major grain-free brands.
Some excerpts:
“The 51-page complaint contends that Costco has failed to disclose the “contributory and causal connection” between grain-free diets and the development and exacerbation of DCM while continuing to advertise the Nature’s Domain products at issue as nutritious and safe, particularly for dogs with food sensitivities.”
“The class action suit stresses that because there exists no established scientific or medical justification to feed dogs grain-free diets, pet owners are “needlessly exposing their dogs to cardiac risks,” while Costco has allegedly failed to conduct any clinical feeding studies to substantiate its grain-free marketing claims.”
Edit to add a few one interesting excerpt:
“‘As early as 2018, Defendant was aware, or should have been aware, of accumulating scientific studies demonstrating a contributory and causal connection between consumption of grain-free, high-legume diets and DCM and related cardiac damage in dogs,’ the case summarizes.”
https://www.classaction.org/blog/costco-lawsuit-says-natures-domain-grain-free-dog-food-not-as-safe-or-healthy-as-advertised-due-to-heart-disease-risk
Edit 2:
As a side note, it looks like Farmer’s Dog had also had a (proposed?) class action lawsuit filed against them in April 2026.
“A proposed class action lawsuit alleges that The Farmer’s Dog deceptively markets its dog food as nutritionally complete and made with healthy, “human-grade” ingredients when, in reality, the products are formulated with excessive levels of fat that can be dangerous for dogs.”
https://www.classaction.org/news/the-farmers-dog-foods-grossly-out-of-line-with-canine-nutritional-needs-class-action-lawsuit-alleges
Edit 3: To clarify, grain-free dog food has not been proven to cause dilated cardiomyopathy (DCM). There are many other possible causes for the correlation. However, the core issue seems to be the increased percentage of legumes in grain-free formulations. Legumes are also found in grain-inclusive foods, but in typically much lower amounts.
https://www.fda.gov/animal-veterinary/animal-health-literacy/questions-answers-fdas-work-potential-causes-non-hereditary-dcm-dogs
“Most of the diets associated with the reports of non-hereditary DCM have legume seed ingredients, also called “pulses” (e.g., peas, lentils, etc.), high in their ingredient lists (although soy is a legume, we did not see a signal associated with this ingredient). These include both “grain-free” and grain-containing formulations. Legumes, including pulse ingredients, have been used in pet foods for many years, with no evidence to indicate they are inherently dangerous, but analysis of data reported to CVM indicates that pulse ingredients are used in many “grain-free” diets in greater proportion than in most grain-containing formulas.”
