The Truth About Corn in Dog Food


Some insist corn is a nutritious dog food ingredient… while others denounce it as nothing more than a problematic cereal grain.

Dog Food CornSo, what should you believe? What’s thetruth about corn in dog food?

Is it good? Or is it bad?

Well, that depends on whom you ask.

In general, anxieties expressed over the use of corn in dog food seem to come from consumers… pet owners, breeders and the like.

Whereas the “Corn is Great” crowd appears to include those who have something to gain from making or selling products made with this controversial grain.

Myths About Corn Promoted
by the Pet Food Industry

Makers and sellers of corn-based foods insist the negative stories about corn are simply unsubstantiated myths and rumors spread around the Internet by simple-minded consumers.

The truth is, the pet food industry itself is guilty of disseminating its own self-serving and myth-based distortions, too.

In fact, most of the exaggerated claims extolling the virtues of corn actually originate within the pet food industry and are unwittingly propagated by naive and well-meaning pet owners.

Here are some of the most enduring myths about corn promoted by makers and sellers of corn-based dog foods.

Myth #1
Corn Has a Low Glycemic Index

The glycemic index is a way of measuring the tendency of a specific food to raise the blood sugar level of an animal. The higher the index, the greater the risk of an unhealthy rise in blood sugar.

Here are the actual glycemic index figures1 for a few common dog food grains…2

  • Corn meal (69)
  • Brown rice (55)
  • Corn (53)
  • Oatmeal (49)
  • Wheat (41)
  • Barley (25)

Compared to most other cereal grains used for making dog food, corn does not have a low glycemic index.

Myth #2
Corn Does Not Cause Allergies

Cheerleaders for corn-based products like to point out that corn is one of the least allergenic ingredients in dog food.

And according to some studies, that is probably true. One report found the incidence of corn allergy to be only 14%.3 And another places corn at just 3% of all allergies.4

Yet to be fair, other reports caution readers not to place excessive value on the accuracy of these studies due to the notable difficulty in confirming the precise incidence of food allergies in dogs.5

In any case, although it may not be a common food allergen, corn still cannot be completely excused as a potential cause.

When searching the Internet for these studies, it’s hard not to notice the thousands of legitimate reports by owners, breeders, forums and veterinary sites reporting corn and other cereal grains as a likely cause of their dogs’ allergies.

And then there’s the (very real) issue of cereal grain quality.

In many cases, problems aren’t so much a matter of allergies to the corn itself but rather to undetected contaminants within that grain.

It’s not unusual to find storage mites, their droppings and expired carcasses in bulk lots of feed grains6. And all of these are known to be notable canine allergens.

So, for these reasons (and until proven otherwise), we believe corn should still be considered a reasonable suspect when investigating the cause of any food-related canine allergy.

Myth #3
Corn Is Highly Digestible

As a whole grain, corn is not easily digestible. Unless the kernel is first refined into a meal or a flour (and then cooked), corn can be very difficult for a dog to digest.

As a matter of fact, corn (and other grains) are only digestible to the extent to which they’re processed.

That’s why even though the grain may be listed as “whole” on a pet food label, it’s nearly always first ground before being cooked into kibble.

And the finer it’s ground, the more digestible corn will be. But also, the higher its glycemic index.

However, to the uninformed, the pet food industry’s claim that corn is “99% digestible” can be misleading. It’s easy to innocently take that statement to mean corn has a high nutritional value, too.

Unfortunately, as you’ll see, that is simply not the case.

Myth #4
Corn Has a High Biological Value

There’s nothing unique enough about corn’s content that makes it a nutritional standout… nothing that can’t be found in, or converted from, some other ingredient. Not even protein.

And to those who insist the protein content of a corn kernel has some important biological value we present the following table…7

Dog Food Ingredients and Their Biological Value

When it comes to its protein usability, corn has a measurably lower biological value.

Myth #5
Corn Is Rich in Vitamins and Minerals

Fans of corn also like to claim the grain is high in anti-oxidants and minerals.

High in anti-oxidants and minerals? Compared to what?

Aside from its energy content, corn’s nutritional completeness is certainly not exceptional.

The Nutrient Balance Completeness Score is a measure of how complete a food is with respect to vitamin, mineral and dietary fiber content. The higher the score of a food, the more complete its nutrients.

According to information gathered by NutritionData.com8 from the USDA’s National Nutrient Database for Standard Reference, theCompleteness Score for corn and a number of other common ingredients are listed here in increasing nutritional value

  • Brown rice (33)
  • Corn (34)
  • Barley (36)
  • Oats (43)
  • Quinoa (45)
  • Wheat (48)
  • Potato (51)
  • Peas (53)
  • Sweet potato (55)
  • Spinach (91)

So, when it comes to judging its vitamin and mineral content, corn is mostly unremarkable.

Myth #6
Corn Is a Superior Source of Energy

Some pet food manufacturers like to point out that corn is a better source of energy – especially for working animals – than meat.

However, science proves this to be yet another myth.

Consumers shouldn’t favor a dog food because “protein” is the first ingredient. They should choose a dog food because meat is the first ingredient.

That’s because meat doesn’t just contain protein – it also contains fat.

Corn is mostly fat free. It’s a carbohydrate.

From a scientific standpoint (and not marketing hype), here’s the actual energy scorecard for each of the 3 macronutrients9 found in all food:

Nutrient Calories per Gram

The following caloric information is based upon the USDA’s National Nutrient Database for Standard Reference and published by NutritionData.com10:

Dog Food Ingredient Calories per Gram

Ounce-for-ounce, science proves meat contains significantly more energy than corn.

The Truth About Corn

So, why is corn used so abundantly in the manufacture of today’s commercial dog foods?

Well, as you’ve just seen, surely not because it could be considered more nutritious.

Then, could corn be “more natural”?

When you study a dog’s natural ancestral history, you won’t find any mention of corn. That is, until the year 1956. For that was the year indelibly marked by the invention of kibble.

So, why did the introduction of kibble bring with it such a dramaticrise in the use of corn in making dog food? What suddenly made carbohydrates (like corn, grains and potatoes) so popular with the pet food industry?

The truth is…

  • Carbohydrates are cheap
  • Carbohydrates are vital to the kibbling process

You won’t find corn in commercial dog food because it contributes some unique nutritional property. No, it’s there simply because it supplies cheap calories to the product.

And starchy carbohydrates play a critical role in a process known asgelatinization… which is absolutely crucial to the workings of kibble machinery.

As proof, how often do you find corn in a raw or canned dog food?

The Bottom Line

In a nutshell, corn makes any pet food you find it in less expensive to produce. And it does this by diluting a recipe’s more costly meat ingredients.

Kibble is simply inexpensive fast food for dogs. And that’s OK. Because corn doesn’t just save money for manufacturers. It also makes dog food more affordable for pet owners, too.

However, to advertise that corn is included in commercial dog food primarily for its nutritional benefits is misleading — and a grossmisrepresentation of the facts.

It may be OK for a dog food to contain corn. However, it’s not OK for a manufacturer to make such outrageous claims about this rather ordinary cereal grain in a deceptive attempt to mislead consumers and to exaggerate its true nutritional value.


  1. Based upon human studies, canine values unavailable 
  2. Brand-Miller J et al, The Glycemic Index Foundation, “The New Glucose Revolution”, New York (2003), pp.291-296 
  3. Fadok V (1994), “Diagnosing and Managing the Food Allergic Dog”, The Compendium 16:12, 1541-1544 
  4. Roudebush P, “Ingredients associated with adverse food reactions in dogs and cats”, Adv Small Anim Med Surg 2002;15(9):1-3 
  5. Chesney, C.J., 2001, “Systematic review of evidence for the prevalence of food sensitivity in dogs”, Veterinary Record, 148:445–448 
  6. Extension Entomologists, North Central States, Federal Extension Service, U.S. Department of Agriculture 
  7. Palika, Liz, The Consumers Guide to Dog Food, New York, Howell Book House, 1996 
  9. Per Modified Atwater Method