Costco Lawsuit Says Nature’s Domain Grain-Free Dog Food Not as Safe or Healthy as Advertised Due to Heart Disease Risk

A proposed class action lawsuit alleges that Costco has deceptively marketed its Kirkland Signature Nature's Domain grain-free dog food as healthy and safe despite scientific research suggesting that grain-free diets high in legumes and pulse ingredients may increase a dog’s risk of dilated cardiomyopathy (DCM), a fatal heart disease.

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.

According to the lawsuit, DCM was historically believed to be a primarily inherited condition mainly affecting certain large dog breeds, such as Great Danes, Irish wolfhounds, and Doberman pinschers. However, after veterinarians began to diagnose the condition in dogs not typically known to be susceptible to it, researchers increasingly explored whether DCM could be diet-induced, particularly in dogs consuming grain-free, high-legume diets, the filing relays.

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.

“In misrepresenting its product and failing to inform consumers of the implications of consuming Nature’s Domain grain-free dog food, while simultaneously marketing the products as safe and healthy, Defendant abuses the public’s trust,” the filing charges.

Rise in DCM diagnoses among atypical breeds sparked scrutiny of grain-free diets, lawsuit says

According to the complaint, dilated cardiomyopathy is a heart disease that causes enlargement and weakening of the left ventricle, which reduces the heart’s ability to pump blood effectively.

The suit explains that the disease progresses in stages. After an initial asymptomatic period with no functional cardiac changes, the case says, dogs may begin to show signs of cardiac damage before reaching clinical heart failure, which includes respiratory distress, exercise intolerance, weakness, fainting, abdominal distention, lethargy and weight loss. In many cases, the complaint says, dogs with advanced DCM die within a year of diagnosis.

Although DCM was historically observed predominantly in larger dog breeds, vets around 2012 began to report increasing numbers of DCM cases and related cardiac damage in breeds not traditionally associated with the disease, the complaint explains.

According to the lawsuit, the jump in unexpected diagnoses prompted researchers to investigate whether diet could be contributing to the disease. The suit contends that growing concerns over diet-induced DCM coincided with the rapid rise in popularity of grain-free dog foods, which gained steam in the late 2000s amid broader consumer interest in low-carbohydrate and gluten-free diets.

Filing claims that human dieting trends fueled the rise of grain-free dog foods

According to the complaint, the popularity of grain-free dog food surged alongside the rise of low-carb paleo, gluten-free, and “Atkins” diets in the 2000s. As pet owners increasingly sought foods they perceived as healthier, grain-free products grew from a niche segment to nearly one-quarter of the dog food market, per the case.

The suit alleges that manufacturers capitalized on these trends by promoting grain-free formulas as superior alternatives to traditional dog foods, particularly for dogs with food sensitivities or allergies.

In place of grains, grain-free dog foods typically incorporate alternative carbohydrate and plant protein sources, including legumes and pulses such as peas, lentils, chickpeas and their derivatives. The complaint states that these ingredients are generally less expensive than animal proteins, allowing manufacturers to reduce production costs while marketing the products as premium offerings.

Despite the popularity of grain-free diets, however, the complaint contends that there is little scientific evidence supporting their use for most dogs and no established medical justification for routinely feeding dogs grain-free foods.

Dog food lawsuit argues that veterinary research, FDA findings challenge grain-free diet claims

In light of increased reports of diet-induced DCM, veterinary cardiologists began promulgating warnings against such diets and recommending immediate feeding changes to reduce the risk of disease progression. According to the complaint, a growing body of peer-reviewed research has not only linked grain-free diets to an elevated risk of DCM and related cardiac damage, but has also shown that dogs diagnosed with DCM experienced improvements in heart function after being switched off a grain-free diet and to a traditional one.

In response to mounting veterinarian reports, the U.S. Food and Drug Administration (FDA) launched an investigation in July 2018 into a possible connection between non-hereditary  DCM and grain-free dieting, the suit says.

According to the complaint, FDA data demonstrated that Nature’s Domain grain-free dog food was ranked the seventh most commonly reported dog food in DCM cases. The lawsuit alleges that Costco and other manufacturers were subsequently asked to aid in the investigation and provide information about their products’ formulations.

The lawsuit references analyses conducted by veterinary researchers, biostatisticians, and epidemiologists that found associations between grain-free dieting and increased left ventricular diameters, and that dogs would live longer on traditional diets than on grain-free diets.

Per the suit, this growing body of evidence put Costco on notice of the potential risks associated with grain-free, high-legume dog foods.

Despite the findings to the contrary, Costco has continued to market its Kirkland Signature Nature’s Domain grain-free products as healthy, nutritious options for dogs without warning consumers of the purported DCM risk, the complaint alleges.

“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.

Costco benefits from lack of public awareness of DCM risks, lawsuit says

According to the complaint, manufacturers in the grain-free dog food industry have concealed and suppressed dietary recommendations by blocking references to veterinary and FDA findings and attempting to undermine the implications of the research. Specifically, the suit alleges that, through extensive lobbying campaigns, manufacturers have been able to use “pressure tactics” that resulted in the FDA in December 2022 announcing that it would release no further updates on its investigation into non-hereditary DCM, purportedly to “encourage research and collaboration by academia, veterinarians, and the industry.”

Consequently, the case asserts, many consumers remain unaware of the connection between grain-free diets and DCM in dogs.

By advertising its Nature’s Domain grain-free dog food as nutritious, tasty and healthy for all dogs, especially those with food sensitivities, Costco effectively omits all contrary recommendations and induces consumers to pay a price premium for dangerous products, the lawsuit contends.

The suit further alleges that Costco has not provided any supporting evidence for its pro-grain-free diet claims, ostensibly because it has yet to conduct adequate feeding studies to assess the safety or efficacy of the Nature’s Domain dog food.

“No reasonable consumer would expect that Nature’s Domain grain-free dog food marketed as healthy and safe would pose a risk to their dogs’ cardiac health, safety, and well-being, or that it would cause or contribute to a fatal heart condition,” the complaint stresses.

The lawsuit emphasizes that pet owners have paid a price premium for products they believed were safe, healthy and supported by science when they otherwise might have chosen a different dog food had they been aware of the risks of a grain-free diet for dogs.

Who’s covered by the Nature’s Domain dog food lawsuit?

The Nature’s Domain class action lawsuit seeks to represent all individuals who purchased Nature’s Domain grain-free dog food in the United States within the last four years.

I purchased Nature’s Domain grain-free dog food. How do I join the lawsuit?

Typically, there is nothing a consumer needs to do to join or sign up for a class action lawsuit when it’s first filed. The time to take action typically occurs in the event of a class action settlement, at which point the people covered by the case, called class members, may receive notice of the settlement with instructions on how to submit a claim form for benefits.

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