While you know you’re supposed to load up on veggies on The Paleo Diet®, sweet corn is not on the menu. Why is that?
In short, sweet corn isn’t a vegetable, despite what food brands might have you believe. We’ll explain why corn is categorized differently based on when it’s harvested, and why eating any type can be harmful to your health.
According to the USDA, corn can be considered either a grain or a vegetable based on when it is harvested. Sweet corn, which is the immature state defined as when the kernels are still juicy, is considered a starchy veggie by the USDA. Only when it’s harvested fully mature and dry, and can be milled into cornmeal, does the USDA consider it a grain. [1]
Of course, most vegetables don’t just “grow into” grains. While it may be an issue of semantics, we consider sweet corn a cereal grain. Regardless of how it may be classified, sweet corn still has the same harmful anti-nutrients of its mature version, and is best avoided.
Sweet corn, unlike vegetables, is bad for your digestion, and can promote weight gain over weight loss. Here are three major ways that eating sweet corn can negatively impact your health.
Here at The Paleo Diet, we recommend focusing on foods with a low glycemic load, which means that the food will only minimally impact blood sugar and insulin levels.
Since corn is high in starch, it’s also high on the glycemic index. [2] That means that corn can spike blood sugar levels, which often leads to fatigue, bloating, and unnecessary weight gain.
Corn was not eaten before the advent of agriculture, let alone Paleolithic times. Since we are designed to eat as closely as possible to the way our hunter-gatherer ancestors did, our bodies have not evolved to handle the consumption of corn, particularly as a staple.
Corn and other cereal grains contain the harmful compounds lectins and prolamins. [3-4] These sneaky anti-nutrients can negatively impact nutrient absorption and also cause inflammation in the body. This digestive disruption can also lead to leaky gut syndrome and can trigger the initiation and development of autoimmune diseases. [5]
If you’re not yet convinced that corn's golden gems can cause your body grief, you’ll be surprised to learn that 92 percent of corn planted in the United States is genetically modified. [6]
GMOs, or genetically modified organisms, refer to any crop whose DNA has been modified using genetic engineering technology. While the health implications of consuming GMOs is a common debate in the scientific community, what we do know is that GMOs create antibiotic-resistant genes in the gut bacteria of those who eat them. (7) That’s bad news if you’re sick and need to take antibiotics!
Since these foods are new inventions—and clearly unavailable to our ancestors' diet, therefore not a Paleo-friendly food choice—their long-term effects on human beings are unknown. (8)
Corn can show up in our food in tricky ways. Read labels carefully: Corn can hide as high-fructose corn syrup, corn meal, corn starch, and even the innocuous-sounding vegetable oil.
High-fructose corn syrup hides in a lot of our foods, even surprising places like yogurt, cereal, ketchup, and salad dressings. This artificial sugar made from corn starch is added to processed food to extend their shelf life and to amplify flavor. Its sweetness has an addictive quality that makes consumers want more, all while adding an unnatural amount of fructose to your diet. In other words, consuming high-fructose corn syrup is like adding table sugar to your meal.
Weight gain and obesity has been directly linked to the consumption of high-fructose corn syrup and is especially a cause for concern for those living with diabetes. [9]
Think you’ll miss your side serving of corn in the summer? You can easily replace it with riced broccoli or cauliflower. We’re especially partial to this Paleo Cilantro Lime Broccoli recipe!
While corn is often considered a vegetable, it’s important to remember that corn is actually a grain. Our bodies are incapable of properly digesting corn, and eating it can cause issues like bloating, inflammation, and weight gain. Corn shows up in in many ways besides just on the cob, so it’s always important to read food labels!
1. AskUSDA [Internet]. Ask.usda.gov. 2021 [cited 7 July 2021].
2. Glycemic index for 60+ foods - Harvard Health [Internet]. Harvard Health. 2021 [cited 7 July 2021].
3. Dabravolski SA, Kavalionak YK. Effect of corn lectins on the intestinal transport of trace elements. J Consum Prot Food Saf. 2020;15(2):163–70.
4. de Punder K, Pruimboom L. The dietary intake of wheat and other cereal grains and their role in inflammation. Nutrients. 2013;5(3):771–87.
5. Mu Q, Kirby J, Reilly CM, Luo XM. Leaky gut as a danger signal for autoimmune diseases. Front Immunol. 2017;8:598.
6. Center for Food Safety, Applied Nutrition. GMO crops, animal food, and beyond [Internet]. Fda.gov. 2020 [cited 2021 Jul 7].
7. Keese P. Risks from GMOs due to horizontal gene transfer [published correction appears in Environ Biosafety Res. 2008 Jul-Sep;7(3):151]. Environ Biosafety Res. 2008;7(3):123-149. doi:10.1051/ebr:2008014.
8. Bawa AS, Anilakumar KR. Genetically modified foods: safety, risks and public concerns-a review. J Food Sci Technol. 2013;50(6):1035–46.
9. Forshee RA, Storey ML, Allison DB, Glinsmann WH, Hein GL, Lineback DR, et al. A critical examination of the evidence relating high fructose corn syrup and weight gain. Crit Rev Food Sci Nutr. 2007;47(6):561–82.
Irene Jay is a Holistic Health Coach and a certified Nutrition Coach from Vancouver, BC.
Dr. Loren Cordain’s final graduate student, Trevor Connor, M.S., brings more than a decade of nutrition and physiology expertise to spearhead the new Paleo Diet team.
One of the original members of the Paleo movement, Mark J. Smith, Ph.D., has spent nearly 30 years advocating for the benefits of Paleo nutrition.
Ironman athlete, mom, author, and nutrition blogger Nell Stephenson has been an influential member of the Paleo movement for over a decade.
As a professor at Colorado State University, Dr. Loren Cordain developed The Paleo Diet® through decades of research and collaboration with fellow scientists around the world.
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