These days, more and more pet owners are asking about gluten-free diets for dogs. It’s easy to see why—in recent years, news has spread about gluten sensitivity and celiac disease, an autoimmune disorder in which the ingestion of gluten causes digestive problems and may lead to damage in the small intestine. Now there’s a broader trend of gluten-free foods being marketed to reduce inflammation, even in people who don’t have celiac. Naturally, advertisements for grain- and gluten-free pet products weren’t far behind. So, this begs two questions: Are these diets the best choice for your dog?
Are Grains and Gluten the Same Thing?
First, it’s helpful to understand the difference between grain-free and gluten-free food for dogs. Gluten, in a broad sense, is used in animal nutrition to describe the protein fraction of a grain. You’ll often see corn gluten and wheat gluten listed on pet food labels—both are added as a source of amino acids, the essential building blocks for protein that are required in pet diets.
Here’s where it gets confusing: the term “gluten” doesn’t mean exactly the same thing in pet nutrition as it does in human nutrition. Corn gluten in pet food, for example, contains protein—but no true gluten as human nutritionists define it.
So, the definition of gluten used by human nutritionists describes the contents of the endosperm (which provides nutrition to a plant embryo inside a seed) of a certain subset of cereal grains (wheat, rye, barley, triticale). Other grains, like oats, millet, corn, and rice, don’t contain the typical components of gluten, namely the proteins gliadin and glutenin.
Gluten can be helpful in cooking—the interactions between these specific proteins are used in baking when fermentation by yeast causes bubbles to form which are trapped in this gluten matrix. While most pet foods aren’t baked, gluten is usually used in making kibble to help the process of extrusion (a common method for manufacturing large quantities of shelf-stable pet foods).
If all grains don’t contain gluten, how do we define a grain? Grains are broadly defined as the small hard seeds of a plant. Even this definition is confusing, because most people talk about “grains” in pet food when referring to cereal grains, or those seeds from grasses that belong to the family known as Poaceae and are commonly eaten by humans, like wheat, rice, and corn.
Of course just like with gluten, the definition is a little muddy as there are a few seeds in pet diets that aren’t cereal grains—namely quinoa but also buckwheat (not related to true wheat), chia, and amaranth. Sometimes these are labeled as “pseudocereal grains,” sometimes they’re labeled as “seeds” rather than grains. Confusing, right?
The take-home is that you can find both gluten-free diets and grain-free diets for dogs. Just know that with “grain-free” kibble, some carbohydrate is currently required to give the food its form. As a result, the source of carbs in those products will either be a root vegetable (like potato, sweet potato, or tapioca) or non-cereal grains / seeds like quinoa or chia.
Signs Your Dog May Have a Gluten Sensitivity, Intolerance, or Allergy
Let’s start off with the fact that much of what we know to be true is found in the scientific literature, where associations are drawn from a large number of pets going to a veterinary clinic or in carefully controlled experiments. From this limited and always changing body of knowledge, we know that the most common food sensitivities and allergies in dogs are to animal-source proteins. Grains and gluten sensitivity have been proven to be a cause of allergies in very few animals.
The best way to find out if your dog has a possible food allergy is a food trial—when you stop feeding a certain food for a few months, then reintroduce it, and see if a problem develops. Keep in mind too, that if your pet is allergic to one grain, it doesn’t mean they’re by extension allergic to all grains, just like being allergic to one meat doesn’t mean all meats are a problem. There’s no good blood test for gluten sensitivity, intolerance, or allergy—generally, the same goes for grains. The best method to “test” is through a food trial.
The most common signs of food allergies, to any type of food protein, in dogs are itching and skin redness or infection. A subset of dogs may have gastrointestinal (GI) symptoms like vomiting or diarrhea, but these appear to be less common than skin signs.
Gluten sensitivities have only been reported in a group of Irish Setters; these dogs didn’t gain weight well and had chronic diarrhea. There were changes seen in the intestines in response to gluten, and the changes and clinical signs were improved after eliminating gluten. There aren’t any reports in other breeds of dogs. Could it be possible that gluten is responsible for less severe signs in other dogs? Of course, we just don’t yet have evidence. Many diets designed for use in dogs with potential food allergies or chronic diarrhea are coincidentally free of gluten, so it’s not difficult to avoid it if your dog has chronic GI conditions.
Does Your Dog Need a Grain- or Gluten-Free Diet?
If your dog has chronic allergies or gastrointestinal symptoms, a food trial is often recommended in which, ideally, you feed a diet from foods to which your pet has been exposed to before. It’s most important to select a new animal source protein. In other words, if your dog has shown symptoms after eating food containing chicken, switch to one with beef. But you can certainly avoid grains easily by picking a carbohydrate-free diet or grain-free diet which uses potato, sweet potato, or tapioca.
If you’re simply trying to avoid gluten in your pup’s diet, you can either pick a grain-free diet, which won’t contain gluten by default, or just avoid the gluten-containing cereal grains of wheat, rye, barley, and triticale. Other grains without gluten—which are safe in gluten-sensitive people—are oats, rice, barley, and “pseudocereals” like quinoa, to name a few.
It’s not clear yet that gluten causes chronic inflammation in dogs or cats or that all grains are problematic in every pet, and it’s unlikely that’s the case. Still, like all food choices, it’s best to find the diet your pet does well on through trying different nutrient compositions and ingredients. Each pet, just like each human, may have specific intolerances that you can’t predict, and you’ll only be able to identify them through experimentation. No matter what, it’s a good idea to rotate diets regardless of the type you select, so you learn more about your dog’s tolerances—and also provide nutrient variety.