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Still seeking a grain of truth

dvm360dvm360 March 2024
Volume 55
Issue 3
Pages: 20
Atlantic City

In the years since experts began hashing about the possible heart hazards of grain-free dog food, thinking has changed. But conclusions remain few, leaving pet owners and their veterinarians to chew on the dilemma.

Popularized as a panacea for pruritus, an answer to allergies, a guardian for the gastrointestinal tract, grain-free diets were once the darlings of the dog food aisle. Then 2014 happened… and reports started to trickle in to the FDA of nonhereditary dilated cardiomyopathy (DCM) in dogs caused by eating certain commercial pet foods, many of which were labeled “grain free.”

As cases mounted, the FDA announced its pledge to investigate, and sales of grain-free canine diets crumbled. Yet today, grain-free bags and cans decorate store shelves, ride checkout conveyor belts and fill kitchen pantries.

Grain-free pet food

Photo: Mikhail/Adobe Stock

In the last year, pet foods labeled as grain-free have seen 5% sales growth, said Danielle Conway, DVM, while presenting a session at the Fetch Coastal conference in Atlantic City, NJ. She also noted that revenues are predicted to hit $53 billion over the next decade.1 “It is here to stay,” she said.

Clearly, there was a shift in the collective attitude toward grain-free canine nutrition. But to digest it requires an understanding of the science behind the probe.

Ganging up on grain-free

DCM, heart chamber dilation secondary to cardiac muscle wasting, occurs genetically in breeds like Doberman pinschers, boxers, great Danes and Irish wolfhounds2; a separate link between DCM and taurine deficiency has been described in golden retrievers3 and English cocker spaniels4. But the cases that turned FDA heads involved dogs that didn’t match recognized breed criteria, and were seemingly nonhereditary.

By 2018, more than 300 case reports of nonhereditary DCM had landed on the FDA’s doorstep: The common thread for many was diets devoid of grain.5 Their recipes swapped cereals like wheat, rice, corn, millet and rye for higher-than-usual proportions of such ingredients as legumes—or “pulses” (peas, lentils and beans)—and potatoes.

In response to the alerts, the agency announced an investigation. As word spread, people stopped feeding grain-free formulations to their pets. Within a year, the FDA had received a running total of more than 500 records for affected dogs (plus reports for 9 sick cats), which included a wide variety of commercial foods.6 “That’s a whole lot of patients and a whole lot of diets out there,” Conway said.

In mid-2019, the FDA named the top 16 brands of grain-free recipes appearing in these canine DCM case reports.6 But the agency fell short of panning grain-free altogether.Instead, they stated that nonhereditary DCM is spun by a complex interplay of genetics, diet and underlying medical conditions.

Carbohydrates and human crazes

If owners were quick to turn their back on grain-free diets after learning of the FDA’s scrutiny, they were even hastier to reject grain in the first place. That’s because pet food choices tend to follow human diet trends, Conway explained. "It’s the belief that less grain, less gluten and less sugar is a healthier person. And we project this onto our animals,” she said.

Glutens have come under fire, and indeed there is the occasional dog with a celiac-like sensitivity to gluten. (Inherited gluten sensitivity has been documented in Irish setters7 and soft-coated wheaten terriers.8) But just as nutrition trends in people become broadened to include dogs, gluten gets generalized to encompass grains.

However, Conway pointed out, not all grains contain gluten. But some do. And pet owners typically do not know the distinction.

Grain-free pet foods exploded in popularity in the early 2000s, for their being sansgluten and, in consumers’ eyes, free of other allergens as well. But seasonal allergies are often mislabeled as food allergies, which are uncommon and usually directed against protein sources.9-11 These allergenic proteins, Conway clarified, are present at higher levels in meats than in grains.

Many people also consider grain-free rations to be low in carbohydrates and, therefore, closer to the ancestral diet of the wolf. Carbohydrates are generally seen as little more than cheap fillers, devoid of nutrients and full of calories.

“Carbohydrates seem to be the macronutrient being vilified at the moment,” she said.“But carbs are so much more than just sugars and starches.”

Carbohydrates power the body. They can be simple - white rice, pasta and plain old sugar… rapid-fire fuel injectors. But those complex cousins, things like whole grains, legumes and vegetables, should not be forgotten. These carbs are healthy sources of fiber and protein, and release glucose at a more measured pace.

Regardless, eliminating grain hardly solves the carbohydrate problem: Ingredients like potatoes, chickpeas and lentils are often used as stand-ins for deleted grains in commercial foods. This is particularly true for kibble, which requires sufficient carbohydrate binder to hold it together.

The social media silo

Pet nutrition is indeed complex. Conway said owners look to the veterinary community for information. She referenced a 2003 American Animal Hospital Association (AAHA) study that found 90% of clients expect nutritional recommendations during their clinic visits, but only 15% leave feeling they have one in hand.12

As for the clinicians, perhaps food talk drags appointments out too long. “Nutrition conversations are time-consuming,” she conceded.

But critical, nonetheless. Especially to counteract the hapless hype that abounds on social media, where folks who are neither veterinarians nor nutritionists dish out feeding directives. “These are the people our clients are going to because they don’t feel they are getting the information from us,” she said. “So, there is a lot of misinformation being spewed out there.”

Grain as hot potato

As omnivores, all canids are adapted to eating grain. But there are some scientifically proven reasons why some dogs might experience adverse effects from grain consumption.

Gluten-containing cereals, wheat in particular, contain amylase/trypsin inhibitors, which have been implicated in various types of inflammation.13 Other wheat compounds, including lectins and amylopectin, also possess proinflammatory properties.14 Inflammation can set any body system on fire, with the gastrointestinal tract and skin particularly vulnerable.

Modern, domestically produced commercial grains differ from heritage lines of yesteryear and from varieties grown abroad.15 Higher levels of gluten and amylopectin, Conway said, could play into the food sensitivities to which U.S.-grown grains have been linked.

Dimming the spotlight on ingredients

The FDA now advises owners to defer to their vets if considering making the switch from a traditional diet. But their apparent flip-flop on grain-free feeding is hardly a roadmap for veterinarians trying to advise clients on pet nutrition.

Although ingredients matter, Conway said, they are not everything. “You could make a really horrible grain-inclusive diet, and a really great grain-free diet. It depends on how it’s formulated.”

She said good nutritional choices hinge on brand scrutiny, and she encourages the veterinary community to mentor owners in evaluating manufacturers on things like feeding trials, digestibility studies and overall quality control.

“I don’t think we necessarily have to recommend avoiding grain-free,” she said, “but we should recommend the companies we trust.”


  1. Grain-Free Pet Food Market Outlook, 2022-2032. Future Market Insights, Inc. Newark, De.
  2. Freid KJ, Freeman LM, Rush JE, et al. Retrospective study of dilated
  3. cardiomyopathy in dogs.J Vet Intern Med. 2021;35:58-67.doi:10.1111/jvim.15972
  4. Kaplan JL, Stern JA, Fascetti AJ, et al.Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets.PLoS One. 2018;13(12).doi:10.1371/journal.pone.0209112
  5. Basili M, Pedro B, Hodgkiss-Geere H. Low plasma taurine levels in English cocker spaniels diagnosed with dilated cardiomyopathy. J Sm An Prac. 2021.doi:10.1111/jsap.13306
  6. United States Food and Drug Administration. FDA investigating potential connections between diet and cases of canine heart disease. July 12, 2018. Accessed December 14, 2023. https://wayback.archive-it.org/7993/20201222194256/https://www.fda.gov/animal-veterinary/cvm-updates/fda-investigating-potential-connection-between-diet-and-cases-canine-heart-disease
  7. United States Food and Drug Administration. FDA investigation into potential link between certain diets and canine dilated cardiomyopathy. June 27, 2019. Accessed December 14, 2023. https://www.fda.gov/animal-veterinary/outbreaks-and-advisories/fda-investigation-potential-link-between-certain-diets-and-canine-dilated-cardiomyopathy
  8. Garden OA, Pidduck H, Lakhani KH, et al. Inheritance of gluten-sensitive enteropathy in Irish setters. Am J Vet Res. 2000;6(4):462-468. doi:10.2460/avjr.2000.61.462
  9. Vaden L, Sellon RK, Melgarejo LT, et al. Evaluation of intestinal permeability and gluten sensitivity in Soft-Coated Wheaten Terriers with familial protein-losing enteropathy, protein-losing nephropathy, or both. Am J Vet Res. 2000;61(5):518-24. doi:10.2460/avjr.2000.61.518
  10. Mueller RS, Olivry TT, Prélaud P. Critically appraised topic on adverse food reactions of companion animals: Common food allergen sources in dogs and cats. BMC Vet Res.2016;12:1–4.doi: 10.1186/s12917-016-0633-8
  11. Gaschen FP, Merchant SR. Adverse food reactions in dogs and cats. Vet Clin North Am Small Anim Pract. 2011;41:361–379. doi:10.1016/j.cvsm.2011.02.005
  12. Suto A, Suto Y, Onohara N, et al. Food allergens inducing a lymphocyte-mediated immunological reaction in canine atopic-like dermatitis. J Vet Med Sci. 2015;77:251–254. doi:10.1292/jvms.14-0406
  13. Arendt M, Fall T, Lindblad-Toh K, Axelsson E. Amylase activity is associated with AMY2B copy numbers in dog: implications for dog domestication, diet and diabetes. Anim Genet. 2014;45(5):716–722. doi:10.1111/age.12179
  14. Junker Y, Zeissig S, Kim SJ, et al. Wheat amylase trypsin inhibitors drive intestinal inflammation via activation of toll-like receptor 4. J Exp Med. 2012; 209(13):2395–2408.doi:10.1084/jem.20102660
  15. De Punder K, Pruimboom L. The Dietary Intake of Wheat and other Cereal Grains and Their Role in Inflammation. Nutrients. 2013; 5(3):771–787.doi:10.3390/nu5030771
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