Many mass-market commercial pet foods contain corn. But what does this mean for your pet’s health?
I recently conducted an informal survey (i.e., I went online and read the ingredients) of some major mass-market pet food brands, and most notably the leading dog and cat “prescription diet” brand. Being a “prescription diet”, the implication is that these foods are supposed to create optimum wellness in our pets. Yet, what I found in my informal survey was that a startling number of these products (unless they were labeled “grain free”) contained some form of corn – whole grain corn, corn gluten meal, corn starch, ground whole grain corn, etc.
There is a lot of controversy surrounding the use of corn in pet foods, which basically seems to be divided between two groups – consumers who do not want to feed their pets corn because they think Corn bad for dogs, cats and the pet food industry that insists that corn is a nutritious form of protein for pets. It is this same pet food industry (and believe me, if you read pet food journals, you’ll see this a lot) that insist that consumers don’t understand the basics of pet nutrition and that they are basically incorrectly applying human nutrition standards to dogs and cats by choosing not to embrace corn as a viable food for their pets.
In our book, Canine Nutrigenomics: The New Science of Feeding Your Dog for Optimum Health, Dr. W. Jean Dodds and I encourage our readers to steer clear of commercial pet foods that contain corn. And, we do this based on sound scientific rationale (sorry, mass-market pet food industry).
Why Corn is a Popular Pet Food Ingredient
Here’s the short answer as to why corn so often shows up in mass-market commercial pet foods: it’s cheap. Corn is a highly subsidized crop, so US farmers grow corn at astounding rates. In 2012, 10.8 billion bushels of corn were grown. [1][2]
And here’s the really interesting part. The vast majority of the corn that is grown is not the type of corn that you would buy in your supermarket’s produce aisle, or even canned or frozen. That type of corn is called “sweet corn”. However, most corn grown by US farmers is called “dent corn,” a type of corn that is processed and used for foods such as cornstarch, high fructose corn syrup, corn cereal, corn oil, livestock feed, ethanol and yes, you guessed it – pet food. [1][2]
Issues surrounding corn in commercial pet foods include:
- Corn is a leading cause of food intolerances in pets.
- Corn contains potentially problematic lectins, which can lead to “leaky gut” syndrome.
- Corn can be contaminated with dangerous mycotoxins.
- Unless it’s organic, the corn in your pet’s food will be made from genetically engineered crops, which we do not endorse (I’ll cover this topic in more detail in a future post).
Let’s take a closer look at some of these issues.
Corn and Food Intolerances/Sensitivities
If your dog is scratching or has gastrointestinal problems, he could suffer from a food intolerance, also known as a food sensitivity. Food intolerances, while generally not life threatening, can pose many long-term health issues for pets, including:
- GI tract problems similar to IBD.
- Chronic itching.
- Chronic burping and gas rumblings (borborigmi).
- Chronic skin, ear and foot infections (especially with the presence of yeast).[3]
If your pet suffers from any of these issues and is eating a diet consisting of grains, including corn, this could be the culprit. The most convenient, quickest and least invasive way to test your pet for a food intolerance is with NutriScan saliva-based food intolerance testing.
Corn and Lectins
Along with wheat and soy, corn contains high levels of lectins, which are sugar-binding proteins that act as natural insecticides and fungicides to protect plants from predators. Lectins are sticky molecules, enabling them to effectively bind to their sugars. The problem is that this stickiness can also cause lectins to bind onto the lining of the small intestine. This can cause damage to the intestinal lining, resulting in a decreased ability to absorb nutrients.
Lectin can also harm the gut microflora, the trillions of beneficial bacteria that live inside the mucosal tissue lining of the gut, resulting in leaky gut syndrome, [4] which is a breach in the lining of the gut. The lining of the gut serves as a barrier that prevents unwanted invaders such as food toxins, toxic chemicals, bad bacteria, undigested food particles and fungi from entering the system. When this lining is compromised, the openings in the gut enable these unwanted and dangerous particles to cross into the bloodstream. [5] Once in the bloodstream, these particles bind to tissues, where they are recognized as foreign invaders by the body’s immune system, which reacts by attacking them. At the same time, the immune system also attacks healthy tissue, which creates inflammation throughout the entire body.[6][7] [5][4]

Corn is not the only food that contains lectins. Actually, some foods that we also consider healthy contain them, such as legumes. Unlike corn, however, these foods contain beneficial qualities, for example legumes are excellent sources of plant-based protein and other nutrients, including phytonutrients and essential vitamins and minerals. In addition, soaking and cooking beans can help reduce their lectin content.
Corn and Myctoxins
A major concern regarding corn involves the risk of contamination with dangerous mycotoxins, such as aflatoxin. Mycotoxins, which are toxic metabolic by-products produced by fungi, can cause serious illness, and even death, to people and animals that eat foods contaminated with them.
A 2007 study found that mycotoxin contamination in pet food “poses a serious health threat to pets”. [8]
A separate study revealed that cattle fed primarily corn developed high stomach acidity that appears to breed a deadly strain of E. coli bacteria. [9]
Yet another study out of the University of Guelph in Canada found that pet foods containing plant-derived proteins are more likely to contain harmful mycotoxins than foods that contain animal-based fish and meat proteins. [10]
These are just some of the issues related to corn in pet foods, which is why I strongly urge you to steer clear of feeding it to your companion dog or cat.
What do you think of corn in mass-market commercial pet foods? Please feel free to let me know your opinion by scrolling below and leaving a comment. I’d love to hear from you!
References
- [1] National Corn Growers Association. (2013). 2012 Facts and Figures in New World of Corn. Retrieved from http://www.ncga.com/news-and-resources/news-stories/ article/2013/03/-2012-facts-and-figures-in-new-world-of-corn ↩
- [2] Williams, K. (2012, October 26). A Tale of Two Corns. Retrieved from http://nefb.wordpress.com/2012/10/26/whats-the-difference-between-field- corn-and-sweet-corn/. ↩
- [3] Dodds, W. J. (2014). Food intolerance: Diagnostic testing & dietary management. Journal of the American Holistic Veterinary Medical Association, 36: 36-42 (summer issue). ↩
- [4] Sisson, M. (2013). The Lowdown on Lectins [Web log post]. Retrieved from http:// www.marksdailyapple.com/lectins/#axzz2ZEGf7fPq ↩
- [5] Robinson, L.E. & Reeves, S. (2013). Review of sIgA’s Major Role as a First Line of Immune Defense and New Indications Regarding Inflammation and Gut Health. Retrieved from http://www.embriahealth.com ↩
- [6] Hyman, M. (2012). How Hidden Food Sensitivities Make You Fat. Retrieved from http://drhyman.com/blog/2012/02/22/how-hidden-food-sensitivities-make-you- fat/ ↩
- [7] Hyman, M. (2013). Three Hidden Ways Wheat Makes You Fat. Retrieved from http://drhyman.com/blog/2012/02/13/three-hidden-ways-wheat-makes-you-fat/ ↩
- [8] Boermans, H.J. & Leung, M.K. (2007). Mycotoxins and the pet food industry: Toxological evidence and risk assessment. International Journal of Food Microbiology, 119 (2007), 95–102 ↩
- [9] Voiland, A. (2007). Health Reasons to Cut Back on Corn Consumption. Re- trieved from http://www.usnews.com/news/50-ways-to-improve-your-life/arti- cles/2007/12/17/health-reasons-to-cut-back-on-corn-consumption ↩
- [10] PetfoodIndustry.com. (2013, August 23). Petfoods with Plant-derived Proteins may Contain more Mycotoxins, Researcher says [Press release]. Retrieved from http://www. petfoodindustry.com/48909.html ↩
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