Grains in Dog Food - A Scientific Outlook

Current trends in pet nutrition favor a grain free, low carbohydrate diet. However, a grain free dog food trend comes without much scientific basis. Many grain free dog foods are wholesome and nutritious and are completely fine to feed for the majority of healthy dogs.

Avoiding grains will not ensure a better quality diet.

In this article we’ll discuss the trend of grain free dog foods and why it may not be a good option for your dog. We’ll examine the most common grains found in dog foods and give nutritional insight into each. Although legumes, such as beans and soybeans technically can be classified as grains, we’ll focus on cereal grains such as wheat and rye.

Using Grains in Dog Food Diets

Grains are defined as seed crops. The seeds are generally small and hard with a hull or outside layer. The three most common are corn, rice and wheat.

The reason grains were introduced into dog foods is because they are often an ideal food source since they are durable and have many applications and uses. Many grains are nutritionally dense and can be a great source of fiber and protein for dogs.

There are no studies suggesting carbohydrates in the form of grains contribute to an increase in disease or obesity. In fact, scientific literature suggests the opposite for obesity – carbohydrates, often in the form of grains, can help satiate hunger and help dogs lose weight (1, 2).

Further research into grain free dog foods found that these diets may even be harmful to dogs (PDF) in multiple cases. The final conclusion of the study was to completely avoid grain free diets unless they’re required for very specific needs of a dog.

It is also important to recognize that many grain free dog foods are not low carbohydrate at all, and instead use starchy vegetables such as potatoes and peas to provide calories in the form of carbohydrates.


Corn is probably one of the most common grains used in dog foods, and one of the most contentious ingredients as well. While corn is considered gluten-free, it has gotten a bad reputation as a an allergenic ingredient and as a “filler” or a poorly nutritious food, but corn does have a lot to offer.

Corn allergies in dogs are actually very rare (345). Of all food allergies in dogs, studies observed that canines are much more likely to be allergic to protein sources such as beef and chicken or gluten in wheat; not corn (6).

Corn on its own will not provide a complete balance of essential amino acids needed for dogs. Obviously any grain on its own would be lacking in terms of balanced nutrition.

When paired with ingredients containing complementing amino acids, corn can be a nutritious part of a balanced diet for dogs. It provides a highly digestible source of complex carbohydrates (789). It’s also a good source of linoleic acid and fiber which have known benefits to dog’s health (101112).

In addition to having nutritional value to offer dogs, another big reason corn is so widely used is likely due to cost. Corn is cheap because it is subsidized annually by the Farm Bill. This makes corn an attractive ingredient in dog foods in order to be economical, and the savings are often passed onto dog owners.


We think of millet as being a common ingredient in bird food, but millet isn’t just for birds. Millet is considered a gluten-free grain, but it is actually more consistent with a seed.

Millet has similar protein structure as wheat and is nutritionally dense, containing calcium for healthy bones, B vitamins that have a variety of important functions in the dog’s body, and antioxidants which have known health benefits (131415).


Sorghum is less commonly used gluten-free cereal grain that is nutritionally similar to oats. It contains complex carbohydrates and is a good source of fiber. Sorghum is also a good source of B vitamins and iron.


Barley is a nutritious source of energy and is high in fiber. Fiber has been shown to have many health benefits for dogs (161718).

It has a relatively low glycemic index compared to common grains such as rice and corn. This has been shown to be beneficial in maintaining fullness in dogs, and helping to control blood sugar (1920).

Barley is nutritionally dense and a good source of manganese, which is involved in bone formation and carbohydrate metabolism; selenium which functions as an antioxidant and is involved in metabolism; Vitamin B1 (Thiamine) which is crucial for cell function; and Vitamin B3 (Niacin) which is important to dog’s skin and digestive health (21).

Barley does contain some gluten, and may not be appropriate for dogs with gluten allergies or gluten sensitivities.


Oats are considered gluten free when pure and can be suitable for dogs with gluten allergies. They are a little higher in fat and protein than some of the other cereal grains.

Oats are a great source of fiber and have been shown to benefit in aiding in satiety in dogs. Oats provide a source of antioxidants and essential nutrients including Vitamin B1 (Thiamine), selenium and copper, which is important for dog’s heart health and can act as an antioxidant (22).


Rice is another very common grain in dog food, especially in hypoallergenic diets. It is considered gluten free. Rice is highly digestible and an excellent source of carbohydrates for energy.

There is very little fat or protein in rice and it does have a higher glycemic index compared to many other cereal grains.

Brown rice, which is less refined than white rice and still contains the bran, is more nutrient dense and high in vitamin E and fiber (23, 24).


Rye is a less commonly used cereal grain. As with most cereal grains it is an excellent source of carbohydrates.

Rye has a high concentration of lignans which help maintain cell health in the same manner as antioxidants (25, 26, 27).


Wheat is another very commonly added grain in dog food and is one of the more contentious ingredients due to its high gluten content. It is the most gluten dense cereal grain among all mentioned.

It is considered to have a high glycemic index and may not be suitable for diabetic dogs.

While gluten allergies are less common than allergies to protein sources such as beef or chicken, wheat is the third most allergenic ingredient in food allergic dogs (6). That percentage is still very small in terms of total number of allergic dogs.

If the dog isn’t sensitive to gluten, wheat can offer a lot in terms of nutrition. It is a dense source of fiber when it is whole grain. There is very little fiber in refined wheat sources where the bran has been removed.

Wheat is a good source of protein, and is high in folic acid, or Vitamin B9 which is important during dog’s pregnancy, and in phosphorous, which is important in maintaining cell function and growth in puppies.

Take Home Message

Grains are one of the most widely consumed food sources in the world both by people and by animals. The most commonly consumed grains are corn, wheat and rice, but there are many other alternatives.

There is some misconception that dogs are carnivores and should eat only meat based diet but there’s no scientific basis to this claim. Dogs are closer to omnivores and eat a little bit of everything. An all-meat diet without supplementation will be lacking in minerals and vitamins, and can cause a whole host of dietary related problems in dogs (28).

Grains, when combined with ingredients with complimenting amino acid profiles are part of a well balanced diet for dogs. Dogs with food allergies are typically allergic to the protein in their diet, such as beef or chicken, and are less likely to be allergic to gluten.

Not all grains contain gluten, and grains can be a part of a gluten-intolerant dog’s diet.

In general, grains provide a rich source of carbohydrates and some can actually contain significant protein levels as well. Protein derived from grain can be a nutritious and healthy source of amino acids for dogs (2930).

Many grains are nutrient dense and supply significant number of B vitamins, antioxidants and fiber, especially when provided as less refined whole grains.

Leave a Reply