Over the past decade, grain-free diet for dogs has become all the rage for pet owners. It's likely you've heard or read how no pet food should contain grains, and all this buzz may leave you wondering: is grain-free food bad for dogs, or is it actually better? Here's what science and vets say about this.

No Grains About It…

The first thing to mention is that taking what's good for people and applying the same concepts to dogs isn't always the best approach as far as veterinary medicine and science are concerned. Similarly, going with a grain-free diet for dogs isn’t always the right way. This is how we came to FDA issuing warnings about grain-free food being bad for dogs and causing heart problems in pets.

This happened because, with the recent advent of ‘gluten-free’, ‘grain-free’, and ‘whole food’ diet fads for humans, the grain-free diet for dogs has successfully taken off in the pet food market as well. Many grain-free dog foods became popular, and a common thought process is, “well, if grains are bad for me, they must be bad for my dog… right?” or “grains are just added filler and have no reason to be in pet food, right?”

In my veterinary practice, I often hear the question, “is grain-free food bad for dogs or do you recommend it?” In short, grain-free dog food has long been controversial with many experts, scientists, and veterinarians that follow an evidence-based approach. Vets have been advising against grain-free foods for a long time but few pet owners listened, which is what resulted in these recent FDA warnings.

That said, the question of grains in dog food is a little more complicated than a simple “it's good” or “it's bad.” Overall, it may be a suitable choice for some dogs but not necessary for most dogs, and there are a few other reasons why feeding grain-free dog foods may not be the best option for your pooch.

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Is Grain-Free Food Bad for Dogs?
(5 Reasons You May Want to Avoid It)

Ask a Veterinarian - Is Grain Free Food Bad for Dogs

1. Food Fraud: It May Not Actually Be “Grain-Free”

Pet owners are often surprised that not all grain-free diets for dogs are actually that, grain-free. In order to understand how this is possible, you need to learn about food substances that are technically grains. Merriam-Webster’s online dictionary defines a grain in the following way (1):

  1. “a seed or fruit of a cereal grass”
  2. “the seeds or fruits of various food plants including the cereal grasses and in commercial and statutory usage other plants (such as the soybean)”

Botanically speaking, cereal grains belong to the family “Poaceae”, which includes wheat, corn, rice, oats, barley, sorghum, spelt, millet, triticale, rye, and many others.

Another group of “grains” has become popular in certain boutique dog foods and is often marketed as “grain-free” dog food diets. They are technically correct, as ‘pseudo-grains’ buckwheat, quinoa and amaranth are seeds – botanically speaking.

So why does this matter?

It matters because dog food companies may be lying to you, which shouldn't be a surprise at this point.

Pet food manufacturers rely on the fact that most people don’t fully understand what grain is. For example, most people think of wheat and corn when they think of ‘grains.’ It is corn and wheat that are currently the most ‘villainized’ cereal grains, associated with GMO production, chemical residues, and poor health.

If you are committed to a grain-free diet for dogs, be sure to read the labels carefully. Sometimes rice or brewer’s barley is in “gluten-free” or “grain-free” dog food diets. These diets should be labeled “No Wheat, Soy or Corn” instead of simply grain-free because rice is a grain.

Stick with reputable companies that are committed to quality product. If you're looking for recommendations for reputable dog food brands, do some research online or ask a canine nutritionist for assistance in choosing a product.

2. It's Not Necessarily Healthier for Dogs

First, let's start with a simple fact: there is no scientific evidence suggesting that a grain-free diet for dogs is a better option for every pet. In fact, the research that has been done on these diets found somewhat opposite results. A 2014 study concludes:

“Labels that read ‘grain-free’ are more harmful to the dog and should not be given unless required for other specific needs.”

Experts staying on top of current research on pet nutrition further confirm this, and generally disagree about switching your dog to a grain-free diet without a good reason to do so (see this, this, this, and this).

Grain-free diets differ significantly one from another

Moreover, the grain-free diet for dogs has many variations, and they are not all created equally. Unless he has a special health condition, your pet's grain-free dog food diet shouldn’t be “low-carb,” but many are.

On the other hand, grain-free diets that are high in protein and fat and low in carbs can be problematic for some dogs (2).

Studies show how feeding your dog grain-free may result in an imbalance of microorganisms in the dog’s digestive tract, and if not immediately then eventually result in flatulence, diarrhea, vomiting, or constipation.

Some dogs that experience digestive upset or inconsistent stools on a high-protein grain-free diet will return to normal once grains or an appropriate high-fiber carbohydrate source is reintroduced. In order to stick with a good balance of all macronutrients and fiber, look for pet foods that provide adequate amounts of fiber through ingredients like green peas, lentils, pumpkin, butternut squash, quinoa, apples, pears, and beet pulp.

Be careful of high-protein diets that contain only one or two sources of fiber. Not all fiber is created equal and different types have different effects on the digestive system.

For example, Ziwi Peak’s Air Dried Beef Formula is a grain-free dog food recipe and almost 100% meat. On a dry matter basis, it comes at 44% protein (high-protein) and 1% fiber. This seems okay on the surface. However, when you look at where that fiber is coming from in the ingredients list, it is from two sources – chicory root inulin (soluble fiber) and dried kelp (seaweed), a source of alginate fiber.

Both inulin and alginates from kelp are types of soluble fiber. Ideally, insoluble and soluble fiber sources should be included in your dog’s diet.

Soluble fiber makes feces less bulky, feeds the “good” bacteria in the bowel, and binds water – making a “gel” that increases water in the feces (3). It also makes speeds up fermentation by some bacteria, which can predispose dogs to flatulence if their diet only contains soluble fiber. Meat-heavy diets that contain only soluble fiber can also predispose some dogs to chronically loose stool or diarrhea, and even over-stress the kidneys.

Insoluble fiber helps to normalize how quickly digested food moves through the digestive tract. It can help to speed things up or slow them down. They also make stools bulkier and a little drier. Your dog’s diet should contain both soluble and insoluble fiber sources. Check his diet for a combination of fiber sources, grain-free or not. This will likely give the best balance of insoluble and soluble fiber.

If you see ingredients on the label from both sides of this chart, your dog’s fiber is well-covered:

Soluble Fiber Sources Insoluble Fiber Sources
Inulin, chicory root Whole Wheat
Seaweed, kelp Oat Bran
Beet pulp Whole Vegetables and Fruits or fruit skins
Whole Fruits Flax
Whole Berries Rye
Psyllium Soybeans
Pectin Peas, Lentils


What the “normal” amount of fiber should be in a dog's diet is widely debated among experts. Typically, less than 5% dry matter fiber is recommended for adult dogs (4). Most commercial dog food diets are 1-2% fiber on a dry matter basis.

3. Dogs are Not Wolves

Many makers of products included in the grain-free diet for dogs promote their foods by claiming that your dog’s ancestral DNA is common with the wolf. This is true, but the comparison is flawed. After a strong scientific inquiry into how similar dogs of today are to wolves, the answer is – not very similar.

Yet pet owners often ask me, “wolves don’t eat grains, so why should my dog?”

This comparison is flawed in that dogs are a different species from wolves and have evolved alongside humans for thousands of years. Dogs are closer to indifferent omnivores, not true carnivores (5), and while wild dogs will hunt for fresh meat, they also get a large portion of their diet from scavenging.

Wild dogs today can and will eat leftover bread from a human garbage bin or half-rotten apples that have fallen from a tree. Wolves typically don’t. Dogs evolved alongside humans and ate what we ate, which includes grains. And 10,000 years of existing alongside humans is enough time to have the dog's digestive system to change and adapt to the new environment and diet, experts say.

Think about this: a similar comparison would be that humans share a lot of common DNA with chimpanzees, as we are all primates. But, do humans have the same nutritional requirements as a chimp? No. We have evolved differently.

4. The Majority of Dogs Can Easily Digest Grains

As dogs have evolved alongside people, their digestive tracts can efficiently digest grain-based calories. As I've mentioned, a grain-free diet for dogs can be a good option in very specific cases. For example, if your pet has allergies, switching to a grain-free dog food diet may seem like the way to go (and sometimes, it is). Many people decide to try a gluten-free or grain-free diet in order to alleviate certain symptoms.

While it's true that going grain-free may help certain canines, it is unlikely to help your dog in the way that you think.

Most dogs with allergies suffer from atopic dermatitis. Dogs can have itchy skin allergies to a variety of different substances, but dogs don’t commonly suffer from gluten or grain intolerances or allergies. It is not impossible – but very unlikely.

Only about 10% of allergies in dogs are caused by food (6, 7, 8). Most of this 10% is caused by eating proteins such as beef, chicken, eggs, and lamb, which studies have found to be the most common allergens. While it does occur, wheat and corn are a more rare causes of allergies in dogs. Statistically, your pet's itchy skin is most likely caused by an allergy to something in the environment, such as pollen, mold, dust mite dander, and cockroach dander.

If you think that your dog is suffering from a food allergy, please talk to your veterinarian. It may be better to try a novel protein (venison, kangaroo) diet or a hypoallergenic diet before cutting out the grains, and put your pooch through the elimination diet trial.

5. The High Cost of Grain-Free Dog Foods

If nothing else, the last thing to mention about grain-free diets for dogs is their expensive price tag. As you have probably already noted, whether cheap brands or those among the top-rated dog foods, the grain-free diet for dogs typically commands a higher cost than their grain-containing counterparts. Animal-based products are almost always more expensive pound-for-pound than plant-based products in pet foods.

Many dog food brands that are grain-free also include human-grade meats. While this can be healthier for our dogs, it commands a higher price as well. Whole fruits, vegetables, and even lentils that are human-grade in dog foods also drive up the price. This doesn't mean that you shouldn't spend an extra dollar on your pet's food if you can afford it, but just be prepared before you make the switch.

In Conclusion

So is grain-free food bad for dogs? In most cases, the answer is likely yes. Grain-free diet for dogs can be good only for certain pets and in very specific cases. In the large majority of instances, there is no need for your pet to be eating a grain-free diet.

Moreover, studies have also found many cases where grain-free diet can be worse for the dog than a grain-containing brand of commercial food.

If you decide to switch to or from a grain-free dog food diet, remember to do so carefully. Anytime you change your dog’s food, it is important to do so slowly.

Start by introducing 10% new food to 90% old food on Day 1 and by Day 7, you should be at 100% new food. If you find that your dog has a soft stool, diarrhea, or vomiting – go back to your old food for a few days and contact your veterinarian.

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